Produced for:

Sheep Easy Breeding Group

Breeding easier-managed sheep

Judith Collins and Joanne Conington

SAC, West Mains Road, Edinburgh, EH9 3JG, Scotland.

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Contents

1 Summary................................................................................................................................. 31.1 Recommendations........................................................................................................... 4

2 Introduction............................................................................................................................ 52.1 Potential characteristics of ‘easy care’ sheep ................................................................. 5

3 Breeding for resistance to disease......................................................................................... 63.1 Nematodes ...................................................................................................................... 7

3.1.1 Faecal egg count....................................................................................................... 73.1.2 Faecal consistency scores and dag scores ................................................................ 93.1.3 Phenotypic and genetic markers for nematode resistance...................................... 10

3.2 Footrot........................................................................................................................... 123.2.1 Genetic variation .................................................................................................... 123.2.2 Footrot lesion scoring............................................................................................. 133.2.3 Use of molecular genetic markers.......................................................................... 13

3.3 Mastitis ......................................................................................................................... 133.3.1 Milk Somatic Cell Counts...................................................................................... 143.3.2 Molecular technologies to quantify mastitis resistance ......................................... 16

3.4 Blowfly strike ............................................................................................................... 184 Breeding for enhanced flock fertility ................................................................................. 19

4.1 Ewe fertility .................................................................................................................. 204.2 Litter size ...................................................................................................................... 204.3 Scrotal circumference ................................................................................................... 214.4 Enhanced ram sexual performance............................................................................... 22

5 Breeding for improved ewe maternal ability and lamb survival..................................... 235.1 Maternal ability traits.................................................................................................... 25

5.1.1 Ease of parturition.................................................................................................. 255.1.2 Care of the newborn ............................................................................................... 265.1.3 Maternal behaviour score....................................................................................... 285.1.4 Milk production...................................................................................................... 29

5.2 Lamb traits .................................................................................................................... 305.2.1 Lamb survival ........................................................................................................ 305.2.2 Gestation length ..................................................................................................... 315.2.3 Parturition............................................................................................................... 325.2.4 Time taken to stand and suck ................................................................................. 325.2.5 Ewe recognition and attachment ............................................................................ 335.2.6 Cold resistance ....................................................................................................... 33

6 Breeding for other traits...................................................................................................... 346.1 Tolerance to food shortages.......................................................................................... 346.2 Longevity...................................................................................................................... 35

6.2.1 Teeth and bone ....................................................................................................... 366.3 Body composition......................................................................................................... 366.4 Wool shedding .............................................................................................................. 366.5 Temperament ................................................................................................................ 37

7 Conclusions ........................................................................................................................... 387.1 Breeding for resistance to disease................................................................................. 38

7.1.1 Nematodes.............................................................................................................. 387.1.2 Footrot .................................................................................................................... 387.1.3 Mastitis................................................................................................................... 397.1.4 Blowfly strike......................................................................................................... 39

7.2 Breeding for enhanced flock fertility............................................................................ 397.2.1 Ewe prolificacy ...................................................................................................... 39

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7.2.2 Scrotal circumference............................................................................................. 407.2.3 Ram serving capacity ............................................................................................. 40

7.3 Breeding for enhanced maternal ability and lamb survival .......................................... 417.4 Breeding for other traits................................................................................................ 427.5 Application to the UK sheep industry........................................................................... 437.6 Recommendations......................................................................................................... 44

8 References ............................................................................................................................. 459 Appendices............................................................................................................................ 72

9.1 Footrot scoring system.................................................................................................. 729.2 Molecular markers for mastitis resistance in cattle ...................................................... 729.3 Maternal behaviour scores at tagging ........................................................................... 759.4 Trait checklist ............................................................................................................... 76

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1 Summary

To maintain the financial viability of UK sheep systems in recent years it has been necessary to reducelabour costs. Better handling and management practices enable greater numbers of sheep to be lookedafter per labour unit but less time for specific tasks may lead to reduced input in areas such assupplementary feeding, health care and supervision and inspection of stock. Furthermore, modernfarmed breeds, bred and raised under intensive conditions, may not be adequately adapted for moreextensively managed systems and may not be able to survive and thrive in situations where there arefewer human inputs. Animal welfare could consequently be compromised due to insufficient animalcare.

It is widely recognised that some breeds are easier to look after compared to others, in particular atlambing time. However, many farmers may be reluctant to substitute their existing breeds for easier-managed ones entirely, to prevent the loss of other important characteristics such as carcassconformation and growth. For this reason, new breeding tools are required, to facilitate within-breedselection for traits that confer greater efficiency and easier management.

The purpose of this fact-finding study was to investigate the key components of ‘easy care’ breedingstrategies and the best approach for the development of practical breeding programmes to achievebreeding for easier-managed sheep. The following groups of candidate traits that may confer betteradaptation to more extensive management systems were considered:

• Resistance to disease (nematodes, footrot, mastitis, blowfly strike and others)• Enhanced flock fertility (ewe fertility, litter size, ram sexual capacity)• Improved maternal ability and lamb survival

o maternal traits (lambing ease, care of the newborn, milking ability)o lamb traits (lamb survival, gestation length, parturition, neonate behaviours, cold

resistance)• Tolerance to food shortages• Longevity (including teeth and bone)• Body composition• Wool shedding• Temperament

Some of these traits are already used in UK sheep breeding schemes (e.g. ewe longevity is predicted inbreeding programmes for hill sheep although it is not recorded separately in practice). Other traits are inthe pipeline to be included in breeding programmes (e.g. direct lamb survival), and others are still beingresearched (e.g. resistance to footrot, nematodes and mastitis).

Difficulties that may be encountered when trying to incorporate some of the traits into breedingprogrammes include:

• insufficient evidence for genetic variation in the trait concerned (e.g. bone quality);• insufficient consensus or knowledge about the ‘best’ trait to be recorded to achieve the breeding

goal (e.g. resistance to nematodes);• traits that are difficult, time-consuming or expensive to record (e.g. behavioural traits);• the fact that ‘hidden’ benefits of trait improvement may not immediately appeal to some breeders

because their cumulative benefits are not realised until some time in the future (e.g. longevity).

However, most of the traits reviewed could potentially be used in UK sheep breeding programmes. Theuse of genetic information from related animals to predict easier-managed traits would be particularlyuseful where the heritability is low or if the traits are difficult to record.

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1.1 Recommendations

Some of the traits considered in the report could be recorded immediately. These include: i) lambsurvival, ii) ewe longevity, iii) ewe fat levels, iv) ‘gestation’ length, v) lambing ease and vi) ram scrotalcircumference. The incorporation of these into indexes would require varying degrees of programmingeffort including full genetic analyses of traits iv), v) and vi) and the identification of associations withother traits that are part of the breeding objective. Faecal Egg Count could also be recorded now but asthe application of the use of this indicator trait for nematode resistance in the UK is yet to be established(e.g. when to sample, how many sampling times, recommended levels of pasture contamination beforesampling etc.), in order to make the best use of this technology it may be preferable to wait until thisknowledge becomes available.

For flocks that have problems with mastitis, the use of Somatic Cell Count (SCC) could be instrumentalin improving resistance to the disease. Further research is needed to quantify the genetic variation inthis trait and to develop a protocol for its inclusion into breeding programmes.

More work is required (which is currently underway) before molecular tests for resistance to disease(footrot, nematodes, mastitis) can be used in practice.

A promising trait for easy care systems is ram libido, as defined by ram serving capacity. Theverification of existing tests from other research groups should be done using UK sheep breeds toestablish a useful protocol that could be used in the field. Further research work is needed before thecommencement of recording.

Further research is also needed for most of the behavioural traits, including the use of either physical orphysiological proxy traits.

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2 Introduction

To maintain the financial viability of UK sheep systems in recent years it has been necessary to reducelabour costs. Better handling and management practices enable greater numbers of sheep to be lookedafter per labour unit (it is now common for each shepherd to be responsible for more than 1000 sheep)but less time for specific tasks may lead to reduced input in areas such as supplementary feeding, healthcare and supervision and inspection of stock. Furthermore, modern farmed breeds, bred and raisedunder intensive conditions, may not be adequately adapted for more extensively managed systems andmay not be able to survive and thrive in situations where there are fewer human inputs. Animal welfarecould consequently be compromised due to insufficient animal care.

It is widely recognised that some breeds are easier to look after compared to others, in particular atlambing time. For example Blackface ewes require less intervention at lambing compared to Suffolks,and lambs take a shorter time to stand after birth (Dwyer and Lawrence, 2005). However, many farmersare reluctant to substitute their existing breeds for easier-managed ones entirely, to prevent the loss ofother important characteristics such as carcass conformation and growth. For this reason, new breedingtools are required, to facilitate within-breed selection for traits that confer greater efficiency and easiermanagement.

To work towards this goal, the ‘Sheep Easy’ breeding group was set up in 2004, comprising breeders ofLlyen, Blackface, Easicare, Romney, Texel and Suffolk sheep. The aim of this group is to sharecommon interests in selective breeding for ‘easy care’ traits, and to work towards the development ofappropriate breeding strategies for easier-managed sheep.

There exists a dearth of genetic information on this subject in UK sheep breeds. In addition, several ofthe traits involve some degree of subjective assessment. Therefore, the development of robust scoringmethods is crucial before any genetic analyses can be adequately implemented or interpreted, prior totheir inclusion in breeding programmes. The purpose of this fact-finding study is to investigate the keycomponents of ‘easy care’ breeding strategies and the best approach for the development of practicalbreeding programmes to achieve breeding for easier-managed sheep. It is envisaged that this initialstudy will lead to the development of a further collaboration with the industry partners which in turnwill lead to the development of new selection indices and breeding recommendations for the sheepindustry. It is also hoped that this project may stimulate breeders to record a wider set of traits than iscurrently undertaken with a view to their ultimate inclusion in selection indices for easier-managed,more efficient sheep.

2.1 Potential characteristics of ‘easy care’ sheep

The trend in Europe towards more extensive rearing conditions in areas of intensive production andtowards the maintenance of farming activity in less favourable regions will lead to considerable changesin rearing management.

Greater emphasis will be placed on the adaptation of animals to their environment and on theirbehavioural response to different stresses. It will be particularly important to achieve harmoniousestablishment of mother-young relationships. Animals will have to be accustomed to the presence ofhuman beings even if the contact periods are only short, because adverse responses can lead to stress.Reduced levels of supervision may mean that disease, injury and parasitism, for example, go undetectedand untreated.

Genetic selection for certain traits could result in the development of breeds and strains of sheep betterable to survive and thrive in such systems. For example, the ‘Marshall easy care’ Romney from NewZealand. Development of this breed began in the mid 1930s and, at least initially, the ewes were notshepherded at all in the hope that sheep would be selected which could look after themselves in difficultterrain. The result is a strain with a reputedly high survival rate, excellent growth rate, good mobility,good wool production and the ability to thrive in harsh conditions. In a study of maternal ability, this‘easy care’ strain had a significantly higher maternal behaviour score than control Romneys, andrequired less intervention by the shepherd. In a 5 year study, lamb survival in the Marshall Romney

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averaged 92%, compared with 88%, 86% and 73% in the Dorset-Romney, Perendale and Romneyrespectively, a result which may be partly due to the smaller litter size of Marshall Romney ewes(Kilgour and de Langen, 1980).

Another example is the Easycare breed developed by Iolo Owen in Wales. The aim was to produce abreed of sheep which would require minimal shepherding and veterinary care and yet offer good meatyields and lambing ratios. This breed sheds its wool, reducing or eliminating labour costs associatedwith shearing and dagging lambs prior to slaughter.

Starting in the 1960s, the breed was derived from the Nelson Welsh Mountain (Welsh Mountain xCheviot) which were crossed twice to the Wiltshire Horn, a wool shedding breed, and selected for woolshedding, no horns and easy care traits. Typically they are not housed and are fed minimum amounts ofconcentrates. Where there is no threat from sheep scab, no dipping is required as there are no incidencesof blowfly on non-soiled parts of the wool. Easycares carry a reasonable fleece of up to 1 - 2 inches inlength through the winter which they cast in the spring. The breed appears to have good conformationand genuine easy care features. Lambs at birth appear to have sufficient wool, are easily born andquickly gain their feet and start suckling. The breed has the potential to significantly reduce labour inputand is recommended where shearing is expensive and difficult to organise. Other hair breeds like theDorper could make good terminal sires or early breeding sheep (Vipond, 2006).

This report will consider the following groups of candidate traits that may confer better adaptation tomore extensive management systems:

• Resistance to disease (nematodes, footrot, mastitis, blowfly strike and others)• Enhanced flock fertility (ewe fertility, litter size, ram sexual capacity)• Improved maternal ability and lamb survival

o maternal traits (lambing ease, care of the newborn, milking ability)o lamb traits (lamb survival, gestation length, parturition, neonate behaviours, cold

resistance)• Tolerance to food shortages• Longevity (including teeth and bone)• Body composition• Wool shedding• Temperament

Each section will include discussions on reported heritability estimates for the various traits and otherrelevant genetic parameters, where available.

The report will conclude with a summary of the different traits and their current and future potential forinclusion in breeding programmes in the UK.

3 Breeding for resistance to disease

Animal health affects production economics, animal welfare, and food safety. Prevention of diseaseswill usually be preferable to curing them, and in cases where there is genetic variation in resistance to adisease, selection may be a useful preventative measure. This approach may be particularly useful inextensive systems where the animals cannot be inspected as regularly as those in more intensivesystems.

Variation in disease resistance (or susceptibility) has been found between species, between breeds andalso between individuals within breeds. Much research into genetic resistance to disease in sheep isfocused on gastrointestinal parasites, footrot and blowfly strike because they impose severe economicconstraints on sheep grazing systems. In addition, the increasing resistance of the causative organismsto commercially available chemical solutions, and public concern over chemical residues in meat,brings into question the long term effectiveness of disease control through chemotherapy. A freshapproach to control the incidence of mastitis in sheep is also required due to the importance of thedisease affecting sheep breeds in the UK, and the costly, ineffective treatments used to control it.

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3.1 Nematodes

Gastro-intestinal nematode infection threatens the health and welfare of livestock, compromises theefficiency of production and is possibly the major disease challenge facing ruminants (Perry andRandolph 1999), costing the UK sheep industry an estimated £84M per annum (Nieuwhof and Bishop,2005).

The increasing problems of attaining effective control of nematode parasites through the use ofanthelmintics due to the evolution of drug resistance in parasite populations is well documented (e.g.Jackson and Coop, 2000; Bartley et al., 2003), and this threatens sustainable sheep productionthroughout the world. The decreasing efficacy of anthelmintics, coupled with the desire to movetowards production systems less reliant upon chemical interventions, has stimulated the search foralternative sustainable control methods. The selection of sheep, particularly growing lambs, withenhanced resistance to nematode parasites is often advocated as a control measure that maycomplement other strategies and, in the longer term, lead to a reduction in the requirements foranthelmintics.

Between- and within-breed genetic variation in resistance to nematodes has been demonstrated in manycountries and production environments. Well known examples include the Merino (e.g. Woolaston andPiper, 1996; Woolaston and Windon, 2001), Romney (e.g. Morris et al., 1997 and 2000a) and ScottishBlackface (Bishop et al., 1996; Stear et al., 1997) as well as feral Soay sheep (Smith et al., 1999).Genetic differences between host animals in nematode parasite resistance have also been observed for avariety of parasite species including Haemonchus contortus, Trichostrongylus colubriformis,Teladorsagia circumcincta and various Nematodirus species. In the UK, the major gastro-intestinalnematode of sheep is Teladorsagia circumcincta, and the mechanisms by which infections caused bythis parasite reduce growth have recently been reviewed by Stear et al. (2003).

Lambs are generally susceptible to infection until about 1 year of age and become increasingly lesssusceptible as they grow older (Courtney et al., 1985; Gamble and Zajac, 1992; Kambara et al., 1993).In contrast, adult ewes are relatively resistant to infection except during late pregnancy and lactation(Courtney et al., 1984). Female lambs have been reported to be more resistant to infection and havelower Faecal Egg Counts (FEC) than males after puberty, although there appears to be no differencesbetween sexes before puberty (Courtney et al., 1985; Barger, 1993; Woolaston and Piper, 1996).

If selective breeding for nematode resistance is to be implemented then it is necessary to be able toquantify resistance. Faecal egg count, the number of eggs per gram of faeces, is the indicator traitcommonly used to assess the level of infection. FECs indicate the product of the adult nematodenumbers and the mean fecundity of the resident parasite population. Other potential indicator traitsinclude phenotypic physiological markers such as plasma IgA activity, pepsinogenaemia, fructosamineconcentrations in the plasma and eosinophilia. Potential genetic markers include the majorhistocompatibility complex and the interferon gamma region.

3.1.1 Faecal egg count

Selective breeding using faecal egg count (FEC) as an indicator trait for animals that have greaterresistance to nematodes has been shown to be effective under New Zealand and Australian conditions(Morris et al., 1997 and 2000a; Woolaston and Piper, 1996; Woolaston and Windon, 2001). In thesecountries, the exploitation of host genetic variation in resistance using FEC in commercial sheepbreeding programmes is now well-established (e.g. the ‘WormFEC’ scheme in New Zealand and the‘Nemesis’ scheme in Australia) leading to reduced dependency on drug usage. Studies have alsodemonstrated that it would be feasible, in principle, to select sheep for resistance to gastrointestinalnematode parasites under typical commercial sheep conditions in the UK where sheep face a naturalparasite challenge, using the same indicator trait (Bishop et al., 1996; Bishop et al., 2004).

Heritability estimates for FECs lie between 0.2 and 0.4 (reviewed in Safari and Fogarty, 2003; see alsoPollot and Greef, 2004a), i.e. moderately high and similar to most performance traits in lambs.However, egg counts are generally a lot more variable than performance traits, giving considerable

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opportunities for genetic progress if they are used as a measured trait in a breeding programme (Bishopet al., 2004). Heritablities for Nematodirus egg counts tend to be slightly higher than correspondingheritabilities for Strongyle egg counts (McEwan et al., 1992 and 1995; Bishop et al., 2004).

Research in the UK has shown that resistance to different species of nematodes tends to be related, withgenetic correlations between the FEC values arising from different species or genera of parasitesgenerally being close to 0.5 (e.g. Bishop et al., 2004). Studies in New Zealand, looking at the geneticcorrelation of FEC for Trichostrongylus and Nematodirus spp. (Morris et al., 2004), found thecorrelation to be approximately 0.43. This means that in practice, it might not be necessary for thepresence of all genera to benefit from selection strategies to improve host genetic resistance.

Vanimisetti et al (2004), in agreement with Courtney et al. (1986), found that selection for indicators ofparasite resistance in nonlactating ewes would have little correlated effect on resistance in lambs,suggesting that response to infection with H. contortus is mediated by different mechanisms in lambsand nonlactating ewes. Therefore they recommend that because the economic impact of parasitism ismuch larger in lambs than in ewes (and because of the apparent lack of correlation between parasiteresistance in ewes and lambs) selection should focus on reducing parasite susceptibility in lambs.

Other studies indicate that in the periparturient ewe, FEC is a moderately heritable trait (Bishop andStear, 2001, Morris et al., 1998; Watson et al., 1995; Woolaston, 1992) and that selection of lambs forincreased resistance to parasitic infection also confers a degree of resistance in periparturient ewes(Woolaston, 1992; Morris et al., 1998).

The direct effects of selection for reduced FEC on lamb growth and other performance traits appear tovary according to production environment, the level and species of parasite challenge and the trait ofinterest (Morris et al., 2000a; Bisset et al., 2001). For relationships between Stongyle egg counts andlamb growth traits, published values from European studies have tended to be negative and strong, e.g. -0.8 between egg counts and live weight in Scottish Blackface lambs (Bishop et al., 1996) and -0.6 forthe same traits in Polish lambs (Bouix et al., 1998). However, Bishop et al. (2004) reported acorrelation of only -0.13 between egg counts and live weight in UK Texel lambs. Under New Zealandand Australian conditions, strong correlations are seldom seen, with values generally being between 0and -0.3 (eg Bisset et al., 1992; Douch et al., 1995; Eady et al., 1998; Pollot et al., 2004), howeverslightly positive, i.e. unfavourable, correlations have also been reported (e.g. McEwan et al., 1992 and1995; Greef and Karlsson, 1998 and Morris et al., 2000a).

Correlations of Nematodirus egg counts with lamb growth are not well documented, although McEwanet al (1992) reported genetic correlations that were more negative than the corresponding correlationswith Strongyle egg counts. In contrast, Bishop et al. (2004) found correlations of performance traitswith Nematodirus egg counts tended to be neutral or slightly positive.

Genotype xenvironment interaction is a term used to describe the phenomenon that occurs when a set ofgenotypes change their relative performance in different environments (Falconer, 1981). Suchgenotype x environment interactions potentially have implications for the efficacy of selectionstrategies to improve host resistance. Pollot and Greeff (2004) working with Merinos in Australiafound that FEC had a high heritability at the extremes of the environmental range, but a moderate levelin the middle. This implies that in low FEC environments, the genetic variation for FEC was high andtherefore some rams have the genetic predisposition to have high egg counts even when the challenge isrelatively low (ie they have no resistance to the parasites at all). Under a moderate challenge regimen,animals are more similar in their genetic control of FEC; presumably the animals with lower resistancein good environments increase their FEC values towards the animals with no resistance. At highchallenges, some animals have the ability to resist the parasites more than others. The way heritabilityvaries across the range of trait environments may have some implications for selection programmes. Forexample, selection schemes could be designed to select against the animals that have high FEC in poorenvironments, as well as selecting those that have a low FEC in all environments.

Experimental results from New Zealand and France, along with theoretical considerations, show thatadded benefit is obtained from genetically reducing FEC, and hence pasture contamination, as sheep

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grazing this pasture subsequently face a lower level of challenge and hence perform better. These areepidemiological effects that give greater apparent responses to selection than predicted by conventionalgenetic theory, both in terms of reduced FEC (Bishop and Stear, 1997) and increased performance(Bishop and Stear, 1999). Experimental verifications of these concepts are provided by Gruner et al.(2002) and Leathwick et al. (2002). In both cases, the grazing of fields by ‘susceptible’ sheep led toconsiderably heavier pasture contamination, increased FEC and reduced performance, than grazing by‘resistant’ sheep. This means that direct benefits of selection will accrue from decreased anthelminticrequirements of selected animals and indirect, flock-wide, benefits on health and performance willfollow from reduced pasture contamination and hence decreased larval challenge (Bishop and Stear,2003).

The cost effectiveness of including parasite resistance in the breeding goal using a selection indexapproach depends on the identification of a reliable and repeatable measure of resistance, therelationships between resistance and other production traits, and the specificity of selection to resistancein terms of other parasite species and non-parasite pathogens. The weighting attributed to parasiteresistance in the breeding goal will be dependent on the degree of parasitism in the productionenvironment and the cost-effectiveness of breeding for resistance relative to other control measures.Independent studies looking at various selection index models indicate considerable value fromimproving resistance to nematode infection, and that these benefits may be obtained without sacrificingmuch direct gain in liveweight (Woolaston, 1994; Amer et al., 1999; Bishop et al., 2004). Somebenefit is predicted to come directly due to the moderate but favourable genetic correlation between liveweight and Stongyle egg counts, however, greater benefit may accrue from the indirect benefits ofreducing pasture larval contamination and reduced use of anthelmintics. Bishop et al. (2004) suggestthat extra benefit will be obtained from basing selection on both Strongyle and Nematodirus egg countsbecause of the higher heritability of the latter and the strong genetic correlation between them.

3.1.2 Faecal consistency scores and dag scores

The accumulated faecal matter in the wool of the breech area is referred to as ‘dags’, which can besubjectively scored. Dag scores (DS) and faecal consistency scores (FCS) have been investigated aspossible indirect indicator traits to breed for decreased worm-related diarrhoea or scouring (Greeff andKarlsson, 1997; McEwan et al., 1997).

Dag score seems to be a moderately heritable trait (between 0.25 and 0.35; reviewed in Pollot et al.,2004) with higher values of heritability at the yearling age than either weaning or hogget age. Manystudies have found dag score to be unfavourably correlated with FEC, suggesting that selection fordecreased FEC will result in an increase in DS (Watson et al., 1986, Baker et al., 1991,; Pollot et al.,2004). However, others have reported a positive correlation between the two traits (Bisset et al., 1992,1996; McEwan et al., 1992).

There are various reports of FCS having a low heritability (Bisset et al., 1994; Bisset et al., 1996; Pollotet al., 2004), although a similar number have estimated higher values (Karlsson and Greeff, 1996;McEwan et al., 1992). McEwan et al (1997) and Greeff and Karlsson (1997) found negative geneticcorrelations between FCS and FEC. However, in a larger study using a flock unselected for FEC,Greeff and Karlsson (1999) found a small positive genetic relationship of 0.1 between FCS and FECand a value of 0.23 was reported by McEwan et al. (1992). Pollot et al (2004) found the correlationsbetween FEC and FCS to be effectively zero.

Dag score and FCS have been found to be highly correlated in all reports indicating that these two traitsare controlled by the same genes and suggesting that FCS could potentially be an indicator trait for DS.This could be useful given that wool is normally removed from around the breech area to make theanimals less susceptible to blowflies, a practice which removes the variation in dags between animals.

The genetic correlations between liveweight and DS and liveweight and FCS have been found to begenerally negative (Watson et al., 1986; McEwan et al., 1992; Bisset et al., 1996) with the exception ofPollot et al. (2004) who reported positive genetic correlations between the traits.

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Dag score and faecal consistency score are clearly not the same trait as faecal egg count. Thus, althoughthese traits are generally used as indicators of host resistance to parasites, their poor relationship withfaecal egg count implies that they would be ineffective to improve host resistance to parasites.However, selection for these traits in their own right could be important to decrease the occurrence ofscouring in sheep, where it is a problem (Pollot et al., 2004).

3.1.3 Phenotypic and genetic markers for nematode resistance

The use of FEC as the only indicator of host susceptibility or resistance to nematodes is time-consuming and costly. Traits other than FEC, particularly various peripheral blood measurements, maybe used to assess resistance to nematodes or host response to infection. If the blood sample taken is thenalso used for further genetic and physiological screening (e.g. for resistance to scrapie, and potentially,for resistance to footrot), then multiple testing of blood samples may well prove to be an economicallyefficient route to assess genetic resistance to several diseases. Furthermore, for T. circumcinctainfections, FECs appear to be relatively insensitive to changes in infection intensity (Bishop and Stear,2000), and additional indicator traits may aid the identification of resistant and susceptible sheep.

There are several phenotypic and genetic markers for nematode resistance in sheep naturally infectedwith nematodes that could potentially assist responses to selection. The phenotypic physiologicalmarkers include immunoglobulin A (IgA) activity (Strain et al. 2002), pepsinogenaemia (Stear et al.1999), fructosamine concentrations in the plasma (Stear et al. 2001) and eosinophilia (Stear et al. 2002).The genetic markers include the major histocompatibility complex (Schwaiger et al. 1995) (Stear, et al.,2005) and the interferon gamma region (Coltman et al. 2001).

Phenotypic markersIdeally, a useful phenotypic marker, in addition to being strongly correlated with nematode resistance,would be easy to sample and its assay would be inexpensive and able to be automated. Potentialphenotypic markers are described below (Box 1).

Box 1: Potential phenotypic markers• IgA is a secreted antibody which is part of the acquired immune response. It has a major role in gut

infections and appears to regulate worm fecundity (Smith et al., 1985; Stear et al., 1995).• Pepsinogen is a precursor of the digestive enzyme pepsin. An increase in pepsinogen activity

therefore indicates the presence of parasites and resultant damage to the gut of the host animal(McKellar et al., 1986; Fox et al., 1989).

• Fructosamine concentration reflects average glucose and protein concentrations as well as the rate ofprotein turnover. T circumcincta can cause a relative protein deficiency as well as an increase inprotein turn-over. Heath and Connan (1991) observed a decrease in fructosamine concentrationfollowing deliberate gastro-intestinal infection, while Stear et al. (2001) reported that naturallyinfected animals with low fructosamine concentrations subsequently acquired more nematodes of allspecies and had shorter, less fecund, female T. circumcincta.

• Eosinophils are a type of white blood cell and are part of the immune response. Changes ineosinophil counts have been associated with resistance to parasitic infection, and they may interactwith IgA to regulate nematode growth (Stevenson et al., 1994; Doligalska et al., 1999; Stear et al.,2002).

Taken from Davies et al., 2005

As a first step towards developing useful phenotypic markers, various studies have looked directly atthe genetic control of parasitic traits describing the properties of the infection in lambs. The parasitedevelopment traits - mean worm length and mean number of eggs in utero in adult female worms -appear to be considerably more heritable than the numbers of larvae or adult worms present in the gut(Table 1; Stear et al., 1997). These results were confirmed by Davies et al. (2005). In contrast, Gaulyet al (2002) reported a heritability value of 0.54 for worm burden yet found worm length to be notheritable, in a small study of Rhoen sheep deliberately infected with Haemonchus contortus.

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Table 1 Necropsy trait heritabilitiesTrait h2 s.e.Worm length 0.53 0.17Worm burden 0.13 0.10No. eggs in utero 0.50 0.16No. of adult females 0.08 0.09No. of adult males 0.12 0.10No. of L4 larvae 0.06 0.09No. of L5 larvae 0.12 0.09Total no. of worms 0.12 0.10Stear et al., 1997

Antibody responses to helminth infection have been investigated on a number of occasions. Forexample, Douch et al. (1995) reported heritabilities of 0.18 for immunoglobulin G (IgG) specific to T.colubriformis and 0.31 for antibodies specific to T. circumcincta. However, Gauly et al. (2002) foundIgG activity not to be heritable. Davies et al (2005), working with Scottish Blackface sheep, reportedstrong and consistent heritabilities for IgA specific to T. circumcincta (0.57 at a mean age of 22 weeks).

Davies et al (2005) also observed strong negative genetic correlations between both IgA activity andeosinophil counts and the worm development traits. This suggests that families with high levels of IgAor eosinophil counts will have shorter, less fecund worms. This result is in agreement with previouswork that associated IgA activity with the regulation of worm fecundity (Smith et al., 1985; Stear et al.,1995). Thus IgA activity and eosinophil count may be useful traits for selection purposes, with the aimbeing to increase values of these traits in order to decrease worm development and fecundity.Confirming this hypothesis further, FEC was found to be positively genetically correlated with wormburden, and negatively correlated with eosinophil and IgA activity (Davies et al, 2005).

Genetic correlations between worm development traits and fructosamine were positive and moderate tostrong (Davies et al., 2005). This indicates that families with high fructosamine concentration havelong, fecund worms and therefore it may be possible to use fructosamine concentration to indicateinfection status. In general, the indicator traits discussed above are moderately to strongly heritableand favourably genetically correlated with both FEC and worm size and fecundity, suggesting that theydo indeed reflect the animal’s ability to respond to infection (Davies et al., 2005). By using theseindicator traits within a selection scheme it would potentially be possible to influence wormdevelopment traits to a greater extent than by using FEC alone. However, selection on these traitswould need to be implemented as part of a structured breeding programme and many factors, includingthe cost and logistical implications, would need to be investigated first.

Genetic markersStudies to detect quantitative trait loci (QTL) for resistance or detect associations with candidates arenow well advanced in New Zealand, Australia, Kenya, US and Europe - including the UK, France, Italyand Spain - although results are not always readily available in the public domain. Full or partialgenome scans have revealed QTL for FEC on chromosome 1 (for T. colubriformis (Beh et al., 2002,Diez Tascon et al, 2005) and H. contortus (Cockett et al, 2005)), chromosome 2 (for Nematodirus(Davies et al., 2006)), chromosome 3 (for T. colubriformis (Beh et al., 2002), general Strongyleschallenge (Paterson et al, 1999, Davies et al., 2005) and Nematodirus (Davies et al., 2006)),chromosome 6 (for T. colubriformis (Beh et al., 2002)) and H. contortus (Cockett et al., 2005)),chromosome 14 (Nematodirus (Davies et al., 2006)), chromosome 19 (H. contortus (Cockett et al,2005)) and chromosome 20 (general Strongyles challenge (Davies et al., 2006)). Further, Marshall et al.(2005) report several significant QTL for H. contortus FEC, in sheep from the ‘Golden Ram’ flockwithin which a major gene for resistance is believed to be segregating. The most consistentlysignificant region is that containing the interferon gamma locus on chromosome 3, although currentevidence suggests that the causative mutation is not within the interferon gamma gene.

QTL for IgA produced in response to Strongyles challenge have been reported by Davies et al. (2006)on chromosomes 3, in the interferon gamma region, and 20, in the MHC region. The study by Cockett

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et al (2005) also found a QTL for packed red blood cell volume (PCV) after H. contortus challenge inthe same location on chromosome 1 as the FEC QTL.

Several studies have also looked at associations between specific genes or markers and FEC. Inparticular, Coltman et al. (2001) found significant associations with a microsatellite within theinterferon gamma gene (IFNG) in feral sheep, and various associations with microsatellites in or nearthe major histocompatability complex (MHC) have been observed (Schwaiger et al., 1995, Janssen etal., 2002). In addition, research in New Zealand has also implicated some QTLs for dagginess (J.McEwan, pers. Comm).

3.2 Footrot

Footrot of sheep is an infectious and highly contagious disease, easily transmitted from sheep to sheepvia pasture, bedding or handling pens, and even spread by sheep that show no clinical signs of disease.The disease results from invasion of epidermal tissue of the hooves by a mixed group of bacteria(Egerton et al., 1969; Roberts and Egerton, 1969), the essential component of this mixture beingDichelobacter nodosus, formerly Bacteroides nodosus (Dewhirst et al., 1990). Footrot-affected sheepfrequently experience pain, discomfort and lameness that affects their ability to compete for feed(Abbot and Lewis, 2005). Affected sheep are also more susceptible to other diseases because of theirweakened condition.

Footrot is widespread and is the major cause of lameness in sheep in the UK (Grogono-Thomas andJohnston, 1997), costing the UK sheep industry an estimated £24M per annum (Nieuwhof and Bishop,2005). In a recent survey of farmers’ practices and attitudes towards footrot (Wassink and Green, 2001;Hosie, 2003), more than 90% of sheep farmers had seen footrot in their sheep in the past year and 31%considered that 6% or more of their flock were affected with footrot.

Control of footrot has largely focused on elimination of virulent isolates of D. nodosus from flocks,prophylactic control of hosts through vaccination, and therapy of affected sheep through the use ofantibiotics and chemicals such as zinc oxide and formalin. None of these measures offers a long-termeasy-care approach to sheep management as they are expensive, not fully effective and will becomeeven less effective if the causative organism becomes resistant to chemotherapy.

It is likely that successful selection of sheep with improved genetic resistance to footrot through theincorporation of footrot resistance into structured breeding programmes would be cost-effective,reducing the current dependency on chemical solutions to control the disease, and would contribute toincreased sustainability by improving animal health, welfare and productivity.

3.2.1 Genetic variation

Breed differences in susceptibility to footrot have long been recognised and confirmed when animals ofdifferent commercial breeds were uniformly exposed to infection by experimental and field challenge(Skerman et al., 1982; Emery et al., 1984; Stewart et al., 1985; Cumlivski, 1988; Lewis et al., 1988).

There are also strong indications that within breeds, contradisposition to footrot infection is responsiveto selection. In the USA, Parker et al. (1983) reported significantly improved footrot resistance inprogeny of Targhee sheep which had failed to succumb to preliminary artificial challenge. In NewZealand, similar advantages have been demonstrated in the Broomfield strain of Corridale sheepdeveloped from animals that have endured intensive field exposure to the disease (Skerman andMoorhouse, 1987).

Estimates for the heritability of footrot liability vary. From an investigation of straightbred Romneyand Perendale ewes and their Booroola Merino crosses, Baker et al. (1986) reported estimates of 0.34for liability to footrot and 0.03 for liability to severe footrot. Heritabilites of 0.53 and 0.23 respectivelywere reported by Alwan (1983) for the same traits in Perendale sheep, and for the Romney breed,Skerman et al (1988) reported heritabilities of 0.28 and 0.17. In a genetic study following challengeand subsequent vaccination, Raadsma et al (1994), working with Merino sheep, found heritability

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estimates of liability to footrot to range between 0.09 and 0.41, depending on the time after challengewhen the inspections were made. Half-sib heritability estimates of resistance to footrot were low tomoderate for single observations recorded pre-vaccination (0.07-0.22) and slightly lower for inspectionsmade after vaccination (0.07-0.15).

3.2.2 Footrot lesion scoring

Using Merino sheep in Australia, a footrot lesion scoring method has been developed, with severityscored on a scale of 0 to 4 (Egerton and Roberts, 1971). This was further developed with sub-classesthat separated clinical signs into 8 categories (appendix 8.1; Raadsma et al., 1994). Successful breedingfor enhanced footrot resistance in Merinos has been described using this approach (Patterson andPatterson, 1989), and Skerman (1985) and Skerman and Moorhouse (1987) have reported thedevelopment of lines resistant to footrot in both the Romney Marsh and Corridale breeds using similarscoring protocols.

3.2.3 Use of molecular genetic markers

Although selection using footrot lesion scoring has been shown to be successful, the development anduse of a molecular genetic test for footrot resistance potentially has enormous advantages. This isbecause of the practical difficulty of objectively scoring feet lesions well, and the difficulty ofclassifying them objectively and repeatably. In addition, with genetic markers, animals that arecandidates for selection do not have to be exposed to infection to determine whether they aregenetically susceptible or not. This method can also shorten the generation interval.

A group of genes important for controlling immune response lie within the Major HistocompatibilityComplex (MHC). These genes show great allelic diversity between individuals and it is thought thatsome alleles are more efficient at initiating an immune response to specific pathogens than others. Dataexist, which suggest an association between genetic polymorphisms within the MHC Class II regionand response to footrot infection (Litchfield et al., 1993; Escayg et al., 1997). Indeed, genetic variationwithin the ovine MHC loci in the class II region, specifically at the DQA2 gene, has subsequently beenused by Lincoln University, New Zealand to develop genetic markers for footrot resistance (Hickford etal., 2004). Importantly, no links were found between the variation of D. nodosus strain (of which thereare at least 9 serogroups covering 18 subsidiary serotypes; Claxton, 1989) and resistance to footrot, soselection of resistant sheep would not be compromised by inter-strain variation.

A footrot test for the New Zealand (NZ) sheep industry, based on their DQA2 alleles, is nowcommercially available (Hickford, 2000) to select more tolerant or resistant animals, without having toexpose the animals to infection. Even though for IP reasons the data associating DQA2 alleles withfootrot have not been published, to date, more than 28,000 sheep have been genotyped in New Zealandfor 258 ram breeder clients. It is estimated that over 1 million sheep have already been born to rams thathave been screened using the NZ test, and the number of tests carried out have been growing by 30%per annum. Recent survey results indicate that on properties that have adopted the technology, zincsulphate use has been reduced by 26% on Merino farms and 55% on Mid-Micron farms, formalin useby 68% and 77% respectively, the number of doses of vaccine by 67 and 55%, and the numbers ofdoses of antibiotics by 66 and 99%. Overall, footrot prevention and control costs have been reduced bybetween 50 and 70% (Greer, 2005).

Current research underway in the UK aims to determine the ‘best’ way to breed footrot-resistant sheep,which includes the further development of the NZ footrot gene test to include greater coverage of thegenome and it’s efficacy in UK sheep breeds.

3.3 Mastitis

Mastitis is considered to be one of the most important health problems in dairy cattle and sheep(Heringstad et al., 2005; Leitner et al., 2004). Mastitis in sheep costs the UK industry millions ofpounds per annum in lost production and premature culling of affected animals. Conington et al. (2006)predicted that the disease results in losses of approximately £11 per ewe.

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Clinical mastitis can be defined as an inflammation of the mammary gland resulting from theintroduction and multiplication of pathogenic microorganisms. The main causative bacteria includeStaphylococcus aureus and Streptococcus agalactiae, (both of which are contagious) and coliforms,streptococci and enterococci. All of these pathogens are found in animals’ environment (bedding,manure and soil). These major pathogens can cause clinical mastitis, which can lead to swelling or painin the udder, changes in milk composition and appearance, increased rectal temperature, lethargy,anorexia and even death.

Other, minor pathogens are also responsible for a rise in Somatic Cell Count (SCC). Sub-clinicalmastitis does not lead to visible changes in milk or the udder, although it is characterised by reducedmilk yield, altered milk composition and the presence of inflammatory components and bacteria inmilk. Both forms of mastitis can have serious economic consequences, due to loss of production andpremature culling of affected animals.

Most of the information available on mastitis in the literature relates to dairy cattle, with well-documented evidence of the causative bacteria, prevalence and incidence of disease, economic costsand control measures, including quantitative and molecular methods of breeding for resistance tomastitis. Much less information on mastitis is reported for sheep, which in turn is dominated by thedairy sheep sector in Mediterranean countries. There is almost no reported data on mastitis in meatsheep. However, a full report on the possibilities of including mastitis in meat sheep breedingprogrammes is the subject of a previous SPARK project by the same author (J.Conington) and is thesubject of a review paper (in press).

Due to the importance of mastitis affecting sheep, and the costly, ineffective treatments used to controlit, a fresh approach is required, potentially through the use of selective breeding for mastitis resistance.Selective breeding for mastitis resistance requires at least a suitable selection trait or molecular geneticmarker, and that the additive genetic variance for this trait is of sufficient magnitude. In addition,effective breeding requires knowledge of its genetic relationship with other traits of economicimportance.

3.3.1 Milk Somatic Cell Counts

CattleUsing breeding as a measure to combat mastitis in dairy cattle has been the subject of considerableresearch effort over the past 20 years or so. In the last decade, genetic evaluations for somatic cell count(SCC) in dairy cattle have become available in most countries. Selecting for SCC rather than for clinicalmastitis (CM) has several advantages: SCC is routinely recorded in most dairy cattle recording systems,contrary to CM, and SCC has a higher heritability than CM (0.15 vs. 0.02; reported in Barillet et al.,2001). As SCC is genetically correlated with CM (a correlation of around 0.7), selection for reducedSCC will lower the incidence of mastitis.

Many studies have shown that unfavourable genetic correlations exist between resistance to mastitis andmilk production traits in cattle. Beilharz et al.(1993) and subsequently Rauw et al. (1998) and Bakkenet al.(1998) used resource allocation theory to explain the negative genetic correlations that many, butnot all, researchers have observed between performance traits and those important for fitness andhealth. Several countries have included mastitis into breeding programmes alongside conventional traitsto stem the deterioration in genetic susceptibility as a result of selection for increased productivity.Mark et al. (2002) list 12 such countries. Veerkamp et al. (1998) estimated that selection to decreasemastitis or limit the rate of increase of mastitis, with a cumulative impact of 1% per year and a nationalpenetration of 50% would result in a national benefit of £0.9m/year, and Conington et al. (2003)reported that increases in mastitis incidence would be halted by the inclusion of SCC into dairy cowgenetic evaluations.

SheepGenetic literature is limited for dairy sheep and not always in agreement with dairy cattle results.Intramammary infections in dairy sheep mainly differ from bovine infections by their etiology and by alower incidence of clinical mastitis versus subclinical mastitis (Emanuelson et al., 1988). In both

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species, coagulase-negative staphylococci are usually the most frequently isolated germs in subclinicalmastitis. They are, however, considered minor pathogens in cattle whereas in dairy sheep they areresponsible for most cases of mastitis caught in milking parlours and consequently appear to be majorpathogens in this species (Barillet et al., 2001).

Selection for resistance to mastitis in sheep is currently underway in the French dairy sheep breedLacaune using SCC as a proxy trait for mastitis and incorporating it into sheep dairy breedingprogrammes (Rupp et al., 2002). The Latxa Breeders’ Associations’ Confederation in Spain(CONFELAC) also began recording milk composition traits including SCC in 2001 (Legarra andUgarte, 2005).

Genetic parametersThere are several heritability estimates for somatic cell count and other milk traits in dairy sheep (Table2.1). The h2 values for SCC are relatively low and range from 0.04 to 0.24, depending on the breed andstage of lactation when they were estimated, tending to increase with days in milk (Barillet et al., 2001).Genetic correlations with other production traits are shown in Table 2.2.

From this table it is clear that there is no consensus among the literature estimates for the geneticrelationships between milk yield and SCC, unlike those for dairy cattle. For example, Legarra andUgarte (2005), working with Spanish Laxta dairy sheep, found that selection for milk yield would havea negative effect on udder depth and teat placement (with implications for milking) but would decreaseSCC. This negative (favourable) genetic relationship between milk yield and SCC is in agreement withestimates for other Spanish breeds and Greek Chios sheep (see table 2.2) but not with the positiveestimates for the French Lacaune breed (Barillet et al., 2001; Rupp et al., 2003).Differences among reported genetic correlations may be related to models, level of production (Spanishbreeds show similar levels of production whereas Lacaune shows a higher level), or data collecting. Itmay be that genetic improvement in sheep dairy breeds has not been implemented to the same degree asthat for dairy cattle and therefore any susceptibility among high-producing sheep to mastitis is not yetapparent. It could also mean that there simply are no antagonisms between selection for increased milkproduction and SCC in sheep. What these estimates do imply, is that any attempt to introduce milksampling as a way to detect mastitis in sheep will need robust estimates of genetic parameters in therelevant population, in particular in relation to key production traits.

Table 2.1: Heritability estimates of milk production traits in sheep

Traits Heritability Population (breed) ReferencesSCC 0.15 (0.04-0.12*)Milk yield 0.34Milk fat 0.50Milk protein 0.63

French Lacaune dairy sheep Barillet et al., 2001

SCC 0.12Milk yield 0.24Protein percentage 0.17

Spanish Churra ewes El Saied et al., 1999

SCC 0.13 French Lacaune dairy sheep Rupp et al., 2003SCC 0.11 Churra ewes Othmane et al., 2002SCC (1st lactation) 0.12SCC (2nd lactation) 0.19SCC (3rd lactation) 0.24SCC (all lactations) 0.04

Manchega ewes (Serrano et al., 2005)

SCC 0.14Milk yield 0.35Milk fat percentage 0.21Milk proteinpercentage

0.31

Greek Chios dairy sheep Ligda et al., 2002

SCC** 0.13Milk yield 0.21

Spanish Laxta dairy sheep Legarra and Ugarte,2005

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SCC 0.04Milk yield 0.34Milk protein % 0.13

Spanish Churra ewes Baro et al., 1994

* increasing with days in milk** Lactational Somatic Cell Score

Table 2.2: Genetic correlation between mastitis (or SCC) and other production traits in sheep

Traits Geneticcorrelation

Population References

SCC-milk yield 0.15 French Lacaunedairy sheep

Barillet et al., 2001

SCC-milk yield -0.15SCC-protein % -0.47

Spanish Churraewes El Saied et al., 1999

SCC-milk yield 0.18SCC-fat content 0.04SCC-protein content 0.03

French LacauneDairy sheep Rupp et al., 2003

SCC-milk yield (ml/d) -0.36SCC-Fat (g/L) 0.04SCC-Protein (g/L) 0.13SCC-Casein (g/L) 0.09SCC-Serum protein (g/L) 0.20SCC-cheese yield (kg/100 L) 0.33

Churra ewes Othmane et al., 2002

SCC-120d Milk Yield (1st lactation) -0.12SCC-120d Protein % (1st lactation) 0.23SCC-120d %Dry Matter (1st lactation) -0,04SCC-120d Milk Yield (2nd lactation) -0.14SCC-120d %Protein (2nd lactation) 0.09SCC-120d %Dry matter (2nd lactation) 0.02SCC-120d Milk Yield (3rd lactation) -0.15LSCS-120d %Protein (3rd lactation) 0.08SCC-120d %Dry Matter (3rd lactation) -0.00SCC-120d Milk Yield (1st, 2nd and 3rd

lactation)-0.16

SCC-120d %Protein (1st, 2nd and 3rd

lactation)0.22

SCC-120d %Dry Matter (1st, 2nd and 3rd

lactation)0.04

Manchega ewes Serrano et al., 2005)

SCC – Milk yield -0.11SCC – Fat % -0.05SCC – Protein % 0.12

Greek Chiosdairy sheep

Ligda et al., 2002

SCC* - Milk yield -0.30 Spanish Laxtadairy sheep

Legarra and Ugarte,2005

SCC – Milk yield -0.37SCC – Protein % 0.37

Spanish Churraewes

Baro et al., 1994

* Lactational Somatic Cell Score

3.3.2 Molecular technologies to quantify mastitis resistance

Molecular genetic markersAs the continuous measurement of phenotypic indicator traits for mastitis resistance or susceptibility istime and labour intensive, the use of suitable molecular genetic markers could be an attractiveproposition, particularly for meat sheep breeds as it does not require milk sampling. However, all theliterature published to date on molecular markers refers to dairy cattle, and only one (unpublished)study is relevant to dairy sheep. A summary of the literature is presented in appendix 8.2.

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Even though there are markers reported for 22/30 cattle chromosomes, the greatest number (6) are onchromosome 23, where the genes responsible for the major histocompatibility complex are located.These genes are responsible for the induction and regulation of immune response and are the focus forseveral other studies related to disease resistance.

In a review on the genetics of mastitis in cattle (Rupp and Boichard, 2003) the immune mechanismsunderlying mastitis resistance pointed towards better functionality of neutrophils (white blood cells),although the associations with them and clinical mastitis were not straightforward and require furtherinvestigation. This review gives a comprehensive summary of the major markers and candidate genesthat have significant relationships with mastitis resistance or susceptibility. Interestingly, in one study,the markers associated with resistance to clinical mastitis were not the same as those responsible forlow SCC indicating that the use of SCC data in QTL studies aimed at reducing the incidence of mastitisshould be carefully evaluated. This highlights the usefulness of markers for traits that are essentiallypolygenic (i.e. expressed by many different genes) and it is notable that to date, no published reportsexist of using molecular techniques for resistance to mastitis in dairy breeding programmes, althoughmost such knowledge stems from cattle.

The hunt for molecular genetic markers in cattle and sheep

In cattle, many Quantitative Trait Loci (QTL) for clinical mastitis and SCC were found by using wholegenome scanning. For example, the QTL for clinical mastitis were localised to Chr. 9, 10, 11,18 and 25(Holmberg & Andersson-Eklund, 2004b; Schulman et al., 2004). QTL for SCC were mapped to Chr. 3,5, 7, 9, 11, 15, 18, 23, 26 and 29 (Boichard et al., 2003; Holmberg & Andersson-Eklund, 2004b;Schrooten et al., 2000; Schulman et al., 2004; Kuhn et al., 2003; Ashwell et al., 2004), especially theQTL on Chromosomes 11, 15 and 18 reached the genome-wise significance level. Hence, chromosomes9, 11 and 18 should be the candidate chromosomes for mastitis resistance in cattle as QTL for clinicalmastitis and SCC are localised on the same chromosome. More markers should be selected on thesechromosomes to detect the fine location of QTL or genes of clinical mastitis and SCC until the realgene that controls the susceptibility of mastitis is known so that it can be used inbreeding for mastitisresistance.

The best route to identify potential molecular genetic markers in sheep would be to align the ovinegenome with bovine genome and find the homozygous chromosomes or regions that are similar (9, 11and 18) by using comparative genome mapping. The next stage would be to select sufficient markers,especially microsatellite markers, on the alignments with other species and detect the QTL for clinicalmastitis or SCC, which then could be used in marker-assisted selection (MAS). Whole genomescanning also could also be used to detect QTL for clinical mastitis and SCC.

Detection of candidate genesDetection of candidate genes for clinical mastitis or SCC is another way to improve the mastitisresistance in sheep. BoLA (bovine leucocyte antigen)-DBR3 gene of the bovine majorhistocompatibility complex (MHC), IgG2 gene and CD18 gene were studied as the candidate genes ofclinical mastitis and SCC in cattle (Kelm et al., 1997). BoLA-DRB3.2*16 was significantly associatedwith lower SCS in Holsteins (P< or =0.05) (Sharif et al., 1998). There was a significant associationbetween BoLA-DRB3.2*23 and occurrence of severe mastitis (P< or =0.05) (Sharif et al., 1998). Todate, the corresponding studies in sheep haven’t been reported. So, it is worthwhile to study theassociation between these genes and clinical mastitis in sheep. Single nucleotide polymorphisms (SNPs)can be detected by using PCR-RFLP or PCR-SSCP, and then the association between the genotype andphenotype needs to be analysed to finally select the favourable genotypes for mastitis resistance andtheir use in marker assisted selection.

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Candidate genes for mastitis resistance in dairy cows

The most extensively studied genes having significant associations with different indicators of mastitisare the MHC class II DRB3 alleles. The general consensus from the majority of the published literatureis that these genes may have potential usefulness as genetic markers of higher or lower risk of diseaseoccurrence in cows. Specifically, the DRB3.2*23 has been associated with severe mastitis from whichcoliforms were the most commonly isolated bacteria (Sharif et al., 1998). The presence of alleleDRB3.2*16 was associated with a higher Estimated Breeding Value (EBV) for SCC, and alleleDRB3.2*8 was associated with increased EBV for clinical mastitis, as was the IgG2b allele and thenormal CD18 allele. Alleles DRB3.2*11, *23, IgG2a, and the recessive allele for bovine leukocyteadhesion deficiency were associated with decreased clinical mastitis. A positive genetic association wasfound between allele DRB3.2*24 and EBV for intra mammary infections (IMI) by major pathogens andbetween DRB3.2*3 and IMI by minor pathogens. Several correlations between EBV for immunologicalassays and EBV for mastitis measures were significantly different from 0. Cows with low EBV for SCStended to have neutrophils that had greater functional ability at maximal immunosuppression, lowserum IgG1, and high numbers of circulating mononuclear cells. Immunological parameters, includingphysiological and molecular markers, are useful aids to understand the genetics of resistance to mastitis(Kelm et al., 1997). It is also possible that the number of DQ genes that a cow actually has, and the ratioof certain T-cell subsets (CD4:CD8) affects their susceptibility or resistance to mastitis. Susceptibilityto mastitis was associated with MHC haplotypes that have a single set of DQ genes, and animals withCD4:CD8 ratio of 0.42 compared to 3.2 for mastitis resistant animals (Park et al., 2004).

Despite the evidence supporting the involvement of the DRB3 locus, there are inconsistent reports ofwhether or not they confer increased or reduced resistance to mastitis. In a review by Rupp andBoichard (2003), three authors showed significant association of allele DRB3.2*24 with susceptibilityto mastitis, more intra mammary infections with major pathogens, more clinical mastitis and higherSCC. However, from other cited studies, allele DRB3.2*16 was associated with either higher or lowercell count. Similar inconsistent trends were reported for DRB3.2*23 and DRB3.2*8. Severalexplanations could be given to explain such trends. First, alleles may be related to resistance orsusceptibility according to environmental conditions (present pathogens), which may be different in thefive studied populations. More likely, the studied polymorphisms were not causal but linked to otherMHC loci involved in mastitis resistance, which would lead to different associations according tofamilies. Thus, analysis of effect of MHC haplotypes rather than single locus should be preferred to geta better handle on the links between genotype and resistance to mastitis.

3.4 Blowfly strike

Blowfly strike is an important disease of sheep, causing the deaths of an estimated 12,000 animals eachyear in the UK (Sargison, 2004). In a survey of organic farmers in Scotland, it was the only diseasespecifically mentioned as a health problem in organic farming (Halliday et al., 1991).

Blowfly strike is caused by the invasion of living tissue by the larvae of dipteran flies, primarily thesheep blowfly Lucilia sericata (MacLeod, 1992; Morris and Titchener, 1997). The maggots feeddirectly on the skin of the infested sheep, creating serious welfare and economic problems. Affectedanimals are restless, dull and reluctant to graze, and kick at the struck area. Secondary bacterialinfection often occurs and the animal may die of septicaemia or the absorption of toxins from liquefiedbody proteins.

Clipped sheep and young lambs with short fleeces are not usually attacked, but as the length of thefleece increases so does the risk of strike (French et al., 1996). The struck area is usually soiled ordamaged in some way to attract flies. The breech is the most commonly infested area. Soiling withfaeces or mycotic infection of the fleece, as a result of high humidity, can trigger an attack (French etal., 1995). Clipping wounds, footrot lesions and headfly lesions may also become infested.

Effective prevention of flystrike remains problematic. Blowflies can travel for several miles, so unlikelice and scab mites, they can not be eradicated from a farm. Furthermore, while modern insecticides are

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extremely effective, in practice correct application of these drugs to achieve satisfactory residualactivity is difficult. There is also evidence for blowfly resistance to insecticidal dips in New Zealand(Litherland et al., 1992) which is probably also the case in other countries.

Differences exist both between and within breeds in susceptibility to fly strike. Litherland et al. (1992)reported a fly strike rate of 0.33, 0.10, 0.10 and 0.00 in Merinos, Romneys, Wiltshires and feral sheeprespectively. These differences appear to be mainly due to the short wool and different fleece structureassociated with summer moulting in the feral and Wiltshire sheep presenting an environment notconducive to strike (see also section 5.4 of this report on selection for wool shedding). The feral andWiltshire sheep had the lowest dag scores over the treatment period. Blowfly strike incidence was farhigher in Merinos than Wiltshire Horn - Merino crosses, but these crosses were inferior to the pure bredMerinos in terms of wool traits (Rathie, 1994).

There exists considerable evidence for large differences between Merino flocks in their susceptibility toflystrike (Atkins and McGuirk, 1979, Dunlop and Hayman, 1958; Raadsma et al., 1989). Atkins andMcGuirk (1979) presented two heritability estimates for the prevalence of flystrike of 0.25 and 0.53.Gilmour and Raadsma (1986) reported an estimate of 0.37 and Raadsma (1991) reported estimates of0.58, 0.53 and 0.10 from three small data sets in which the prevalence of blowfly strike was very high.These data support the view that the predisposition of sheep to flystrike is in part geneticallydetermined, with potential scope for within-flock genetic improvement, at least within the Merinobreed.

An alternative approach to the problem is to introduce new genetic material into the population in anendeavour to make sheep less susceptible to blowfly strike. Of interest in this respect is the WiltshireHorn breed in which fleece wool is shed annually (Slee and Carter, 1961, 1962; Ryder, 1969).

4 Breeding for enhanced flock fertility

Number of lambs weaned per breeding ewe has a greater influence on productivity and profitability ofmost sheep enterprises than any other trait (Matos et al., 1992). Net reproductive rate is determined byseveral components, with fertility (number of ewes lambing per ewe joined), prolificacy (litter size;number of lambs born per ewe lambing) and lamb survival (see section 4) having the greatest influence(Wang and Dickerson, 1991).

In the male, testicular size has long been considered one of the most likely criterion from thephysiological, genetic and practical perspective to improve reproductive performance of related females(Land, 1973; Bindon and Piper, 1976; Walkley and Smith, 1980). The value of testicular size as anindirect selection criterion for improvement of female reproduction is dependent on the heritability oftesticular size and the genetic correlation between testicular size and female reproductive traits.

Sexual performance of rams is highly variable (Terrill, 1937; Price, 1987) and strongly influences flockfertility (Matos and Thomas, 1992). Rams that exhibit relatively rapid ejaculation rates are capable ofinseminating a greater number of ewes per unit of time than males with poorer libido or matingtechnique (Kilgour and Whale, 1980; Perkins et al., 1992). Tests for ranking rams on sexualperformance are repeatable (Snowder et al., 2002) and reliable predictors of sexual performance underfield conditions (Ibarra et al., 2000), potentially allowing breeders to evaluate the mating competence ofindividual males before they are employed in a breeding programme.

In the U.S., number of lambs born in a given interval is the only reproductive trait currently geneticallyevaluated. However, other reproductive trait measures are being studied, particularly those dealing withaccelerated lambing or lambing more than once per year, for possible incorporation at a later time. InAustralia and New Zealand Estimated Breeding Values are produced for litter size born, and SheepGenetics Australia currently offers Lambplan and Merinoselect customers Australian Sheep BreedingValues for scrotal circumference at post-weaning, yearling and hogget ages.

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4.1 Ewe fertility

Fertility does not usually receive direct emphasis in selection programmes, since it is subject tocontinuous natural selection, and reported heritability estimates average less than 0.10 (Fogarty, 1995;Safari and Fogarty, 2003). However, heritability estimates are on average positive, and the importanceof the trait indicates it merits attention, at least in flocks/environments where mean performance is low(less than 90%; Bradford, 2002).

Ewes dry in any year can be culled, or at least not used to produce replacements, and rams should beconsistently selected from dams that have lambed every year.

4.2 Litter size

There is an abundance of evidence for differences between and within sheep breeds in prolificacy (egTurner et al., 1962; Owen, 1971; Fahmy, 1996) which is mostly attributable to ovulation rate(Hanrahan, 1980). Mean values range from about 1.5 to 4.0, excluding the involvement of major genes.Hanrahan (2002) reported that divergent selection for ovulation rate in the Finn breed resulted in theHigh line (selected for high ovulation rate) having a mean ovulation rate 2.2 times that of the Low line(selected for low ovulation rate) confirming the availability of a considerable amount of geneticvariation. Analysis of the variation within the lines did not yield any evidence that a gene with largeeffect was involved. It is likely that a similar degree of genetic variation is available for exploitation inany population of sheep but the rate of selection response will depend on the actual mean value.

The heritability of ovulation rate is generally greater than that for litter size as a result of the influenceof embryo wastage (Hanrahan, 1982). Weighted mean heritability estimates based on numerous studiesfor number of lambs born per ewe lambing (litter size) and ovulation rate are low at 0.13 and 0.15respectively (Safari et al., 2005). A previous review (Fogarty, 1995) reported mean estimates for thesame traits of 0.10 and 0.21 respectively, although estimates of the heritability of ovulation rate for theprolific Finn and Romanov breeds were considerably higher at 0.50 and 0.39 respectively.

In a recent review, Safari et al (2005) reported that the number of lambs born per ewe joined was highlygenetically correlated with both its components: litter size (0.89) and fertility (0.73). These correlationswere higher than those for number of lambs weaned per ewe joined with litter size (0.62) and fertility(0.73). Ewe fertility was moderately genetically correlated with both ewe rearing ability (0.44) andlitter size (0.44). On the other hand, litter size had a small negative genetic correlation with ewe rearingability (-0.14).

Bradford (1985), in a review of previous literature, concluded that an annual increase of 1-2% inaverage litter size could be achieved by selection on this trait. There is also the possibility of ‘jumpstarting’ the process by an initial screening of exceptionally prolific ewes from a larger population toestablish the foundation flock (Clarke, 1972; Hanrahan, 1982; Sakul et al., 1999).

Waldron and Thomas (1992) estimated that adding information on ovulation rate would increase rate ofgenetic change in litter size by 23% compared to use of litter size data only. An experienced operatorcan measure ovulation rate rapidly and accurately by means of laparoscopy but the extra cost ofobtaining the information may be justified only in breeding flocks with an effective marketingprogramme for improved breeding stock (Bradford, 2002).

However, an undesirable side effect of increased average litter size is an increase in the incidence oftriplet and higher order multiple births (Bradford, 1985). Mortality amongst multiples is usually higherthan amongst single-born lambs, for reasons including a lower body weight (Smith, 1977; Hinch et al.,1983; Elving et al., 1986; Gama et al., 1991; Fogarty et al., 2000) and an increased risk of poor maternalbehaviour (Dwyer and Lawrence, 2005). Furthermore, multiple-bearing ewes (and their lambs) will beat greater risk from nutritional deprivation than their single-bearing counterparts, both pre and post-partum, unless management is tailored to the litter size of individual ewes. In a hill environment thenutritional quality of the grazing may make it unlikely that the ewe will succeed in carrying more thanone lamb through pregnancy without some constraint on the viability of the lambs at birth (e.g. low

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birthweight; Robinson et al., 1999). Her ability to produce sufficient milk to support adequate growth inher lambs is also dependent on good nutrition (O’Doherty and Crosby, 1996; Bizelis et al., 2000). In anextensive environment, therefore, a large litter size may be associated with impaired lamb survival, andthe lower litter size often seen in breeds traditionally managed in these environments may beattributable to some degree of natural selection (Deag, 1996; Dwyer and Lawrence, 2005).

There may also be a genetic link between production traits and litter size. Selection for lean tissue inBlackface and Coopworth breeds resulted in increased mean litter size in the lean lines compared todivergently selected or control lines (Conington et al., 1998; Dwyer et al., 2001; McEwan et al., 2001).A similar increase in litter size with selection for reduced backfat has been seen in mice (Armbrust andEisen, 1994). Ap Dewi et al. (2002) reported a small negative genetic correlation between litter sizeand ultrasonic fat depth (-0.01) and a positive correlation between litter size and ultrasonic muscledepth (0.35) in Welsh Mountain sheep. Genetic correlations between litter size and weaning, post-weaning and adult weights are generally positive and moderate in magnitude (Safari et al., 2005).Taken together, these results indicate that the increased litter size in intensively vs. extensivelymanaged animals may be a consequence of selection for production traits rather than (solely) aconsequence of extensive management. Confirming this further, a comparison of Scottish Blackface(hill) and Suffolk (lowland) ewes following similar nutritional management systems showed that theSuffolk ewes still had a higher average litter size than the Blackface ewes (Dwyer and Lawrence, 1998).

Single gene effects

The discovery that the high prolificacy of Boorola Merino sheep was due to a gene with a large effecton litter size (Davies et al., 1982; Piper and Bindon, 1982) provided a new perspective on the geneticsof fecundity in sheep and this new paradigm quickly led to evidence for major genes for prolificacy inother sheep populations (eg Cambridge (Hanrahan and Owen, 1985); Icelandic (Jonmundsson andAdalsteinsson, 1985); Javanese (Bradford et al., 1986); Belclare (Hanrahan, 1991) and Romney (calledthe Inverdale gene; Davies et al., 1991)). Studies of ovulation rate using molecular genetic techniquesin these and other breeds have since identified the major genes involved (see Hanrahan, 2003, for a fulldescription).

4.3 Scrotal circumference

Particularly since Land (1973) drew upon common hormonal mechanisms governing reproductivedevelopment in males and females to postulate that selection to improve female reproductive traitscould be based upon measures of testis size and growth rate in related males, considerable research hasbeen directed at studying testicular traits. Several authors have indicated that males with larger testeshave either greater sperm production or higher daily sperm output (Cameron et al., 1984; Purvis et al.,1984; Mukasa-Mugerwa and Ezaz, 1992). In the live ram, scrotal circumference is highly correlatedwith, and is a reliable indicator of, testis weight (Notter et al., 1981), and testis weight correlates wellwith daily sperm production (Lino, 1972). Selection of rams for greater potential to produce increasednumbers of spermatozoa on a daily basis will enhance flock pregnancy rate and lambing percentage(Memon, 1983). Póti et al. (1999) reported a positive correlation between scrotal circumference andlibido of 0.56, but no significant correlation between scrotal circumference and sperm quality.Mickelsen et al. (1981) suggested that there is no direct relationship between ram fertility and scrotalcircumference.

Scrotal circumference increases with age (Ruttle and Southward, 1988; Moore and Sanford, 1985) andshows seasonal variation (Mickelsen et al., 1981; Moore and Sanford, 1985).

In contrast to low heritabilities for female reproductive traits, moderate heritabilities have beensummarised for scrotal circumference in sheep (means of 0.24 and 0.21 reported by Fogarty (1995) andSafari and Fogarty (2003) respectively). Scrotal size has also been correlated with fertility, ovulationrate, litter size, and age at puberty in several species. In beef cattle, strong relationships have beenreported between testis size (measured as scrotal circumference) at about 1 year of age and measures ofage at puberty and yearling fertility in females (Brinks et al., 1978; King et al., 1983; Toelle and

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Robison, 1985; Smith et al., 1989). Also, divergent selection for cow fertility in tropical conditions ledto a significant positive correlated response in scrotal circumference between 9 and 18 months of age(Mackinnon et al., 1990). After 22 generations of selection for increased litter size in mice, a realisedgenetic correlation between testis weight and litter size of 0.42 was reported (Eisen and Johnson, 1981).

Results in sheep, summarised by Matos and Thomas (1992), are variable, but suggest a generallypositive relationship of testis size with ovulation rate and a somewhat smaller positive relationship withrealised prolificacy. Waldron and Thomas (1992) reported a positive genetic correlation betweenscrotal circumference and ovulation rate of 0.20, but a correlation of -0.25 between scrotalcircumference and litter size. Haley et al (1990) reported that selection for testis diameter in crossbredsheep did not change ovulation rate or litter size but increased the number of lambs born per ewe mated,apparently through an increase in fertility. Duguma et al. (2002) found that rams with larger scrotalcircumference induced a significantly higher fertility and general productivity in their ewe mates, andsuggested that the use of rams with larger testis measurements would allow a reduction in the number oframs required for breeding each year and increase the overall reproductive efficiency of the flock. Al-Shorepy & Notter (1996) reported genetic correlations between scrotal circumference at 90 days (SC90)and spring fertility and fall litter size of 0.29 and 0.36 respectively. Fossceco & Notter (1995) reporteda genetic correlation between SC90 and ewe fertility of 0.20.

Walkley and Smith (1980) indicated that greater genetic gain in selection for a ewe reproductivemeasure could be achieved if direct selection for a ewe reproductive trait was complemented withindirect selection based on a male trait with an approximate heritability of 0.35 and genetic correlationwith the female reproductive trait of >0.30. Scrotal circumference may meet these minimum criteria.

However, although various reports indicate that scrotal circumference is moderately to stronglypositively correlated with liveweight at different ages (Brash et al., 1994a,b; Fossceco and Notter, 1995;Al-Shorepy and Notter, 1996; Duguma et al., 2002), others have reported a negative correlationbetween the two traits (Land, 1982; Burfening and Davis, 1998; Haley et al., 1990) raising doubts aboutthe value of including information on scrotal circumference in a selection programme to improve littersize.

If selection for testicular size is to be practised, scrotal circumference growth from 90 to 180d (withsome adjustment for liveweight) appears to be the trait of choice because it generally has the highestheritability (Matos et al., 1992; Fossceco & Notter, 1995; Al-Shorepy & Notter, 1996). In addition, thistrait does not need to be adjusted for ram type of birth (single or multiple; Matos et al., 1992).

4.4 Enhanced ram sexual performance

Sexual performance is highly variable among populations of rams (Terrill, 1937; Price, 1987) whichmeans that a relatively rapid response to selection is very likely. Most mature rams readily court,mount and mate oestrual ewes, whereas the intensity of sexual behaviour varies from asexuality to highsexual activity. This fact has led to the development of procedures to rank rams for breeding soundnessbased on their sexual behaviour (Wiggins et al., 1953; Blockey, 1976; Kilgour and Whale, 1980;Perkins and Fitzgerald, 1992). Such tests, which assess the rate at which rams attain successful matingswhen housed with oestrous females, have been shown to accurately predict the breeding performance ofhigh and low performance, female-oriented rams (Stellflug et al., 2006). These tests are highlyrepeatable (Snowder et al., 2002) and are reliable predictors of sexual performance under fieldconditions (Ibarra et al., 2000). They can also identify rams with high sexual performance at an earlyage (14 months; Snowder et al., 2002).

High sexual performance rams (ie males that exhibit relatively rapid ejaculation rates) are capable ofservicing more ewes per unit of time and therefore produce more lambs than males with poorer libido(Perkins et al., 1992; Stellflug et al., 2006). High-performing rams are also less likely than low-performing rams to repeatedly mate with the same females (Price et al., 1996). This is an importantconsideration when choosing rams for sheep breeding programmes in which the female:male ratio isrelatively high, as in many extensive range breeding situations.

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Bench et al (2001) found that sire sexual performance classification influenced the proportion of high tolow performing ram lambs produced. 82% of high-performing ram lambs were sired by highperforming sires, whereas 60% of low performing ram lambs were sired by low performing sires.Furthermore, the average number of ejaculations attained was significantly higher in sons born to high-performing sires versus sons born to low performing sires. The greater breeding success of highperformance rams compared with low performance rams is probably related to their greater sexualmotivation (more mounts and ejaculations), rather than being attributable to general dominance (Erhardet al., 1998) or differences in ability to efficiently perform the motor patterns associated with mountingand copulation (Bench et al., 2001).

These results suggest that there is an important genetic component to sexual performance and libido insheep. Heritability estimates of 0.33 (Kilgour, 1985) and 0.22 (Snowder et al., 2002) for the servingcapacity of rams support this conclusion. Response to selection for serving capacity should therefore befavourable, with selection resulting in rams capable of mating with more ewes, improving thereproductive efficiency of the flock and reducing the number of rams needed.

Wilkins and Kilgour (1978) found that lambing success was significantly greater for the daughters ofhigh-performing rams but the number of lambs born to ewes that lambed was very similar for the twogroups, suggesting no difference in the ovulation rate. This result is supported by Bench et al. (2001)who found no significant difference in ovulation rate or the number of days between first and secondbehavioural oestrus periods in daughters of high and low performing sires. However, daughters of highperforming sires were significantly younger at first behavioural oestrus than daughters of lowperforming sires. This is important because early maturing females may attain more oestrus cyclesbefore being bred, thus improving their conception rate as ewe lambs (Price, 1985). Breeding animalsearly in life can shorten the generation interval for genetic selection and may increase the lifetimenumber of offspring produced (Hulet et al., 1969). Snowder et al. (2004) found correlations of sexualperformance of rams with number of lambs born and weaned to be nil to low, depending on the breed.

5 Breeding for improved ewe maternal ability and lamb survival

Lamb mortality is a major constraint to efficient sheep production (Alexander, 1988; Haughey, 1991)with the vast majority of lamb deaths occurring within 1-3 days of birth (Nowack et al, 2000; Southeyet al., 2004)1. The first critical stage is the birth process itself, dystocia representing one of the majorcauses of mortality (Kerslake et al., 2005). After birth, survival of the newborn will depend largelyupon the quality of the interactions with the mother and her ability to provide the neonate with anassured source of nutrition, protection and guidance (Haughey, 1993).

High lamb mortality could be reduced substantially by a short period of labour and by maternalbehaviours which protect the nutritional and thermal state of the lambs (Alexander, 1988; O’Connorand Lawrence, 1992)2. This is particularly important in more extensive management systems whereewes must be able to conceive, carry, give birth to and rear their young with little (or substantiallyreduced) human intervention.

Selective breeding has been advocated as a means of improving lamb survival and ewe rearing abilitywithin breeds (Lindsay et al., 1990; Haughey, 1991). However, lamb survival to weaning has a lowheritability (0.02 – 0.13) suggesting that the scope for genetic selection to improve this trait is limited 1 A recent study (Southey et al., 2004) where specific causes of mortality were grouped into ‘dam-related’ (egdystocia and starvation), ‘pneumonia’, ‘other diseases’ and ‘other’ categories found that mortality in the dam-related category was highest in the first week (3.2%), but it dropped below 0.3% in the second week and wasvirtually non-existent after the forth week of age. In contrast, mortality in the pneumonia category was almostconstant for the whole of the 7 week study period, ranging between 0.5 and 0.8%. Overall, mortality droppedfrom 9.8% in the first week to 1.7% in the second weeks and gradually decreased to 1% by weaning.

2 Maternal behavioural traits expressed at birth associated with lamb survival include: maternal licking andgrooming, low-pitched bleating, absence of aggression and lamb desertion, co-operation with lamb suckingattempts, ewe selectivity and lamb recognition, and maintenance of close contact between ewe and lamb(Reviewed in Dwyer and Lawrence, 2005).

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(Hall et al., 1995; Lopez-Villalobos and Garrick., 1999; Morris et al., 2000b; Fadilli and Leroy, 2001;Cloete et al., 2002) and that lamb survival is controlled mainly by non-genetic factors3. Nevertheless,recent work has shown that when lamb mortality was analysed as component traits - ‘disease’, ‘damrelated’ (including dystocia and starvation), ‘pneumonia’ and ‘other’ - the heritability of the individualtraits was slightly higher (0.09, 0.16, 0.19 and 0,14 respectively; Southey et al., 2004) supporting thesuggestion of Cundiff et al (1982) that selection on components of mortality is likely to be moreeffective than selection solely on mortality, regardless of cause. Mortality differences in sheep breedsassociated with different causes have also been reported by Nash et al. (1997), Mukasa-Mugerwa et al.(2000) and Nguti et al. (2003), among others.

Based on a number of studies, the weighted mean heritability for ewe lamb-rearing ability (number oflambs weaned/number of lambs born) was very low at 0.06 (Safari et al., 2005). However, Purser andYoung (1983) reported that lamb-rearing ability was a repeatable trait, and that the more lambs reared,the better the subsequent performance appeared to be. If the lamb was not reared from the ewe’s firstparity, lamb mortality at age three and parity two was 26.8% but if the previous lamb was reared, themortality was only 13.5%. Morris et al (2000b) found that environmental variances due to permanentmaternal effects (for example uterine capacity, pelvic width, milking and maternal ability) were foundto contribute mostly to the repeatability of ewe lamb-rearing performance, providing evidence thatimproved lamb survival has to be seen mainly as a successful partnership between mother and offspringthrough pregnancy, parturition and lactation (Everett-Hincks et al., 2005).

Various authors (eg Alexander et al., 1990b; Cloete & Scholtz, 1998 and Kuchel & Lindsay, 1999) havereported breed and line differences in lamb survival traits (eg length of parturition/ease of birth andneonatal progress of lambs). Such differences may have arisen through relaxation of selection pressurefor a particular trait or traits, particularly if traits have a negative genetic correlation with productiontraits. For example, hill and upland sheep breeds are more adapted to harsh environments and minimalhuman intervention than more intensively managed lowland sheep breeds that have been selected andmanaged for greater production of meat, wool or milk (reviewed in Dwyer and Lawrence, 2005).

It appears, however, that there are several candidate behaviours and traits, of both ewe and lamb, whichwould confer a survival advantage on the new-born lamb, regardless of whether they are transmitted viaa genetic or experiential route. Identification of these adaptations is an important first step if breeds thatcurrently appear unsuitable for less intensive systems are ever to be managed under more extensivesystems (Dwyer and Lawrence, 2005).

Conington et al. (2001, 2002) predict that using multi-trait selection indexes, improvements in maternalcharacteristics can be achieved alongside increasing lamb weaning and carcase weights, with littlechange in subjective lamb carcase quality traits. Key potential index traits include lamb loss from birthto weaning (including lambs born dead), litter size at weaning (own lambs only) and average weight oflambs weaned (including weight of lamb fostered on). Including lamb survival as a trait of the lamb aswell as lamb losses in the index is predicted to reduce lamb ‘wastage’ between birth and weaning(Conington et al., 2002).

In the U.S., evaluation of maternal performance is achieved by recording number of lambs born andcalculation of a ewe productivity index: pounds of lamb weaned per ewe per lambing. Eweproductivity is calculated only for ewes that wean at least one lamb. Weights of weaned lambs areadjusted for lamb age, lamb sex, and ewe age (but not for type of birth and rearing) and are summed toderive ewe productivity. Maternal effects on lamb weaning weight are predicted in the current within-flock analyses, but maternal weaning weight Expected Progeny Differences (EPD) are not currentlyreported.

In Australia and New Zealand, EBVs are produced for number of lambs weaned.

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5.1 Maternal ability traits

5.1.1 Ease of parturition

A prolonged labour increases the possibility of brain trauma and hypoxia in the neonate (Haughey,1993) and impairs sucking, locomotor activity and thermoregulation in lambs (Haughey, 1980; Ealesand Small, 1980; Bellows and Lammoglia, 2000; Dwyer, 2003), increasing the chances of death whensubjected to cold stress or mismothering.

Differences in length of parturition between breeds (Alexander et al, 1990b; Fahmy et al., 1997; Cloeteet al 1998) and lines (Cloete and Scholtz, 1998) have been reported suggesting that there is somegenetic variation for this trait. However, heritability estimates were below 0.05 for both SA MuttonMerino and Dormer breeds (Cloete et al., 2002) and 0.17 for Merino ewes with a small service sireeffect amounting to 0.03 (Cloete et al., 2003). This trait was, however, subject to significant maternaleffects (m2) - computed variance ratios amounting to 0.14 in Dormers and 0.15 in SA Mutton Merinos –indicating that the inheritance of ease of parturition is likely to be mainly maternal (Cloete et al., 2002).

However, embryo transfer between Blackface and Suffolk ewes revealed that the lamb may not bepassive in the birth process but can actively contribute to its ease of delivery (Dwyer et al., 1996). Lambcharacteristics such as birth weight and sex both contribute to the incidence of birth difficulty (Smith,1977; Dwyer, 2003). Likewise, singleton and triplet lambs experience more birth difficulty than twinlambs (see section 4.2.3 below), an effect seen more strongly in Suffolk ewes than Blackfaces (Dwyer,2003).

Lambe et al. (2006) reported no significant change in the incidence of ewes requiring assistance atlambing as a result of selecting Scottish Blackface ewes using a breeding index designed to improveboth carcass and maternal traits (Conington et al., 2006), compared to a control line or to a line selectedby normal commercial (visual) methods. However, lambing difficulties were significantly affected byewe sire and lamb sire (suggesting a genetic component), year, ewe age (highest at 2-years-old), lambsex (male>female), still births (higher) and ewe pre-mating weight (higher weights = less assistance).

Further studies on genetic relationships between lambing difficulties and other traits would be useful tohelp make future breeding decisions to improve productivity whilst maintaining high standards ofanimal welfare in extensively managed flocks.

Pelvic dimensionsAn important component of ease of delivery is the pelvic dimension of the ewe (McSporran andFielden, 1979; Haughey et al., 1985; Cloete et al., 1998; Bilbe et al., 2005). In Merino flocks selectedto improve the ratio of lambs weaned to lambs born (‘lamb-rearing ability’) the main outcome of theselection process has been an increase in the speed and ease of parturition of the selected line overcontrol lines (Cloete and Scholtz, 1998; Cloete et al., 2003). Similar responses have been seen with‘easy-care’ Romney ewes (Knight et al., 1988; Kilgour and de Langen, 1980). With both breeds,selection for lamb-rearing ability is associated with an increase in ewe pelvic dimensions (Knight et al.,1988; Kilgour and Haughey, 1993).

It is possible that assisting ewes at parturition may have reduced natural selection for ease of birth andlarge pelvic dimensions in ewes of more intensively managed breeds. Comparisons of Blackface orRomanov ewes with the Suffolk breed have shown that both Blackface and Romanov ewes tend to havea quicker and easier birth process than Suffolks (Dwyer et al., 1996; Fahmy et al., 1997; Dwyer andLawrence, 1998; Dwyer, 2003). Comparative studies of Soays and Suffolks have demonstrated that therelative pelvic dimensions in Soays (scaled for differences in body weight) were over twice as large asSuffolks (Silva and Noakes, 1984).

Bilbe et al. (2005), using CT scanning to measure pelvic capacity in Scottish Blackface ewes, founddifferences in mean pelvic dimensions of daughters from different sires indicating that genetic variationexists within the breed.

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Larger trials are necessary to quantify genetic properties of dystocia and pelvic measurements and theirrelationship with other production traits before selective breeding for large pelvic capacity can berecommended.

5.1.2 Care of the newborn

Fundamental to the survival of the lamb is the formation of a close and exclusive attachment or bondbetween the ewe and her lambs to ensure their early sucking and colostrum intake (Nowak et al., 2000).Specific behaviours of the ewe (licking and grooming, low-pitched bleating, absence of aggression andlamb desertion, co-operation with lamb sucking behaviours) promote ewe–lamb recognition and a closeassociation between the ewe and lamb (Alexander, 1988; Nowak et al., 1997, 2000). Suppression ofolfactory cues is detrimental for maternal acceptance (Poindron and Lévy, 1990). Ewe behaviouraround lambing time has a large effect on lamb survival, particularly in extensive situations (Nowak,1996) and may also affect weaning weight of lambs and thus ewe productivity (O’Connor et al., 1985).

IsolationIsolation from the rest of the flock during and after parturition is an important preliminary step in theformation of the mother-young bond as it protects the ewe from disturbances, prevents separation ofnewborn lambs from their dams and reduces interference or lamb stealing by other ewes (Gonyou andStookey, 1983, 1985).

The amount of time that the ewe spends isolated from the flock, and her propensity to seek isolation, isaffected by breed and by parity. Whereas isolation seeking appears to be common in hill ewes (Hewsonand Wilson, 1979), less than 50% of Lacaune and Border Leicester ewes (Lécrivain and Janeau, 1987;Alexander et al., 1990a) and less than 2% of Merinos (Stevens et al., 1981) are reported to preferisolation at lambing. Multiparous ewes tend to show greater isolation seeking behaviour thanprimiparous ewes (Gonyou and Stookey, 1983; Alexander et al., 1990a), which may be related todecreased fearfulness at separation from flockmates with the more experienced ewes (Viérin andBouissou, 2002). Characteristics of the birth site per se appear to be less important to lamb survivalthan the ewe remaining undisturbed with her lambs for at least 6 h (Murphy et al., 1994).

In one study the period that ewes remained on or near the birth site was found to be heritable (h2 = 0.20;Cloete et al., 2003). Szantar-Coddington (1994) found that fertility-flock Merino ewes remained ontheir birth sites for 266 minutes compared to 251 minutes for control ewes. Knight et al., (1989) foundthat Marshall Romney ewes (selected for rearing ability) grazed from their birth sites 46 minutes afterbirth, while control Romneys did so after 27 minutes. Therefore, the general pattern from all thesestudies was that ewes selected for lamb-rearing ability tended to remain longer on or near their birthsites than control line contemporaries

Birth site selection

Wet, windy and cold weather are important factors in the deaths of lambs from hypothermia(Alexander, 1962; Obst and Ellis, 1977; Alexander et al., 1980; McCutcheon et al., 1981), thusselection by the ewe of an appropriate site in which to lamb may influence lamb survival. In studieswith Merino ewes, provision of shelter can reduce lamb mortality in poor weather by up to 50%(Alexander and Lynch, 1976; Lynch et al., 1980; Alexander et al., 1980). Expression of appropriateshelter-seeking behaviour would therefore be an important ewe behaviour that promotes lamb survival.

Adult ewes in full fleece seek shelter only when they are outside their own thermoneutral zone (Lynchand Alexander, 1976; Alexander et al., 1979; Duncan et al., 2001). Shorn ewes make greater use ofshelter than full-fleeced ewes (Alexander and Lynch, 1976) as do breeds, such as the Lacaune, whichhave relatively thin fleeces (Lécrivain and Janeau, 1987). However, neither Merino or Corriedale ewes(both woolly breeds) seek shelter unless wind speeds exceed 32 km/h with rain, although mortality ofnewborn lambs increases at wind speeds above 18 km/h (Obst and Ellis, 1977). Thus, ewes tend to seekshelter for their own thermal comfort rather than to protect their newborn lambs.

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Lactating ewes appear to seek shelter more frequently than at other times (Pollard et al., 1999).However, this may reflect the use of shelter by lambs during inclement weather, and the desire of ewesto remain with their lambs, rather than shelter-seeking behaviour of the ewe, particularly as shelter useon the day of parturition was lower than during lactation (Pollard et al., 1999).

There are few breed comparisons of sheltering behaviour between intensive and extensively managedsheep and, as described above, sheltering behaviour may be more influenced by ewe fleececharacteristics than other aspects of management. Other experiments suggest that use of shelter isrelated to familiarity with the environment, which may again be a more important influence than breed(Lynch et al., 1980).

There are, however, breed differences in selection of birth sites related to topographical and physicalfeatures of the environment (Alexander et al., 1990a). On level pastures lambing sites for Merinos wererandomly distributed, but on pastures with slopes ewes preferred to lamb at elevated sites. By contrast,both hill and upland (Welsh Mountain, Scottish Blackface, Cheviot) and lowland (Suffolk) ewes choselambing sites at the edges of the pasture rather than elevated sites (Alexander et al., 1990a).

Taken from Dwyer and Lawrence, 2005

Ewe-lamb recognition and bondingThe ewe forms a memory for her own lambs that allows her to restrict maternal care exclusively to herown offspring (‘selectivity’) (Poindron et al., 1984a; Lévy et al., 1995). As ewes are selective for theirown offspring, a lamb that fails to form an attachment with its dam will not be cared for by any otherewe and will not survive. Likewise, the offspring of a non-selective ewe will not thrive, as it is unlikelythat the ewe will produce sufficient milk to feed several lambs. The behaviours that promote selectivityinclude grooming and ewe–lamb contact (Baldwin and Shillito, 1974; Poindron et al., 1980; Alexanderet al., 1986; Poindron et al., 1988; Lévy et al., 1991; Hernandez et al., 2001).

Experimental results suggest that lowland ewe breeds managed intensively tend to show poorermaternal care at birth than hill breeds normally managed more extensively. For example, breedcomparisons of grooming behaviour have shown that, in French breeds, Romanov and Prealpes du Sudewes (hill breeds) spend more time licking their lambs than Ile-de- France (lowland meat breed) orLacaune (intensive dairy) ewes (Le Neindre et al., 1998; Poindron et al., 1984b). Likewise in the Britishbreeds, Blackface ewes show more grooming behaviour than Suffolk ewes and make more low-pitchedbleats immediately after birth (Dwyer and Lawrence, 1998, 1999a, 2000; Dwyer et al., 1998). Suffolkewes, particularly primiparous ewes, show more aggression towards their lambs, are more likely todesert a lamb, and are less co-operative with the sucking attempts of their lambs than Blackface ewes(Dwyer and Lawrence, 1998; Pickup and Dwyer, 2002). The differences between Blackface andSuffolk ewes in the onset of maternal behaviour also appear to be related to maternal attraction to herlambs in the immediate postpartum period. In tests where ewes are offered a choice between their ownand an alien lamb of similar appearance, Blackface ewes are quicker to approach and spend more timewith their lamb than Suffolks, (Pickup and Dwyer, 2002) although both breeds clearly recognised theirown lambs. Similarly, Dalesbred (hill) ewes are more attracted to their young lambs than are Jacobewes (Walser et al., 1983).

When managed as a single flock Blackface ewes maintain consistently closer spatial relationships withtheir lambs than Suffolk ewes throughout lactation (Dwyer and Lawrence, 1999b, 2000; Pickup andDwyer, 2002). Blackface ewes are also more active than Suffolk ewes (standing frequency, Dwyer andLawrence, 2000) and Blackface ewes made significantly more vigilance postures (the ‘head-up’posture, Pickup and Dwyer, 2002). Breed differences in lamb sucking behaviour also exist with Suffolkewes receiving a higher frequency of sucking attempts than Blackface ewes in the first few days afterbirth (Dwyer and Lawrence, 2000). However, Suffolk ewes terminate a greater proportion of shortersuckles than Blackface ewes (Dwyer and Lawrence, 2000), such that Blackface ewes receive a higherproportion of successful sucks throughout lactation (Pickup, 2003).

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These breed differences may have arisen through a relaxation of selection pressure on maternalbehaviour in intensive systems with human interventions (e.g. confinement of ewes and lambs inindividual pens for the first day of life) such that variation in maternal care has less influence on thesurvival of the lamb. Breed differences persist in ewes reared under identical conditions, and sire effectson maternal behaviour can be seen in cross-bred ewes (Pickup, 2003). This suggests that the effects onmaternal behaviour are primarily genetic, although nongenetic, experiential transmission of maternalcare (through maternal grooming, for example, as has been reported in rats, (Francis et al., 1999)remains a possibility.

Maternal cooperation with sucklingThe maternal environment to facilitate suckling, as provided by the dam, has been found to play a rolein the neonatal progress of lambs (Kuchel and Lindsay, 1999; Cloete and Scholtz, 1998; Cloete et al.,2002) and has a small genetic component (heritability of 0.11; Cloete et al., 2003). For example, theinterval from standing to apparently suckling was shorter in a Merino line that was selected for multiplerearing ability than in a parallel line that was divergently selected against multiple rearing ability. Theline difference was partially, but not wholly, accounted for by the inclusion of maternal co-operationwith the first suckling attempts of the neonate in the model of analysis (Cloete and Scholtz, 1998).Ewes selected for rearing ability were less likely to circle and back than control line ewes and they weremore likely to adopt a posture to facilitate suckling.

5.1.3 Maternal behaviour score

One method of measuring maternal behaviour of sheep is to use a scoring system, developed byO’Connor et al. (1985), based on the proximity of the ewe to her lamb as it is handled (appendix 8.3).Maternal behaviour scores (MBS) are attributed to ewes based on their response to the handling of theirlambs at tagging, within 24 h of birth. A five-point scale is usually used, with higher scores awarded toewes which remain closer to their lambs as they are tagged in the field.

The score has been shown to be related to both postnatal lamb survival and weaning weight (O’Connoret al., 1985; O’Connor, 1996; Lambe et al., 2001; Everett-Hinks et al., 2005; Sawalha et al., 2006), andvaries with ewe genotype (O’Connor et al., 1985; Alexander et al., 1990b). In general, Merino ewesshow a higher level of lamb desertion at handling than Romney, Border Leicester or Perendale ewes,and Cheviot ewes are intermediate. A modified version of the score used with Blackface and Suffolkewes suggested there were no breed differences at 24h old but that Blackface ewes approached closer totheir handled lambs at 72h than Suffolks (Dwyer and Lawrence, 1998).

O’Connor et al. (1985) found a significant effect of ewe age on MBS. For each year increase in eweage, MBS increased by 0.26 units, in ewes of 6 genotypes. Lambe et al. (2001) found MBS to increasewith parity with differences in MS between ewes of different ages following a less predictable patternindicating that maternal experience of the ewe is an important factor. This is in agreement with thefindings of Cloete et al (1998) and O’Connor and Lawrence (1992) working with Merino and ScottishBlackface ewes respectively.

Estimates of heritability for MBS vary but are consistently low (0.13, Lambe et al., 2001; 0.09, Everett-Hincks et al., 2005). Lambe et al (2001) estimated a moderate, positive genetic correlation (0.4)between MBS and the average weight gained by lambs from birth to marking although the geneticcorrelation between MBS and weight gained to weaning was close to zero (0.02).

It should be noted that the MBS is not just a measure of the care and attachment of the dam to hernewborns but is also a measure of temperament of the ewe and its reaction to the presence of humans(Dwyer and Lawrence, 2005; Sawalha et al., 2006). The Romanov ewe, for example, is considered tobe a better mother in terms of her licking and grooming behaviour and attachment to the lamb incomparison to the Lacaune (Le Neindre et al., 1998). However, Romanov ewes have a greater flightfrom humans and stood further from their handled lambs than Lacaune (behaviours that would haveearned them a lesser Maternal Behaviour Score). These responses are considered to be due to thegreater emotivity of the Romanov and not to a poorer quality of maternal care. In studies where Merinoewes were selected for temperament by measuring their responses to a variety of tests (such as

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behaviour within an enclosed box, see section 5.5 of this report) the ‘calm’ ewes spent longer groomingtheir lambs than ‘nervous’ ewes, and bleated more frequently to their lambs (Murphy et al., 1998).Lamb mortality in these lines was also lower in the ‘calm’ ewes in comparison to the ‘nervous’ animals.Ewes previously selected for their ability to rear lambs also show behavioural differences in anapproach avoidance test indicative of increased ‘calmness’ (Kilgour and Szantar-Coddington, 1995).

Everett-Hincks et al (2005), working with Coopworth sheep in New Zealand, suggest that ifmanagement practices and environmental conditions are conducive to high levels of litter survival, thenthe incorporation of the MBS into the animal selection programme is likely to be of little benefit asgenetic variation and consequently heritability for MBS and litter survival are small. However, ifmanagement practices and environmental conditions have not been integrated in such a way to enhancelitter survival, then the MBS may have a place. However, a new measure of maternal behaviour as itrelates to lamb rearing success is needed for flocks with higher litter survival rates if litter survival is toincrease further.

5.1.4 Milk production

Increased milk production of range ewes is associated with increased lamb survival and growth (Burrisand Baugus, 1955; Boyazoglu and Treacher, 1978; Torres-Hernandez and Hohenboken, 1980). Thetime period when milk production most significantly influences lamb growth occurs before 6 weekspostpartum (Slen et al., 1963; Snowder and Glimp, 1991), as may be expected due to the naturaldecrease of lamb dependence on milk and increased consumption of forage and/or creep feed.Improving milking performance and lamb production of range ewes could result in significanteconomic returns to most sheep production systems (Snowder et al., 2001b).

Poor milk production is often associated with short-term gestations in ewes less physiologicallyprepared for lactation and that exhibit less mammary development than full-term gestating ewes(Rattray et al., 1974). Heavier body weight has been associated with ewes of better condition andhigher milking capability (Peart, 1968; Gibb and Treacher, 1982) and the level of nutrition can alsoaffect ewe milk production (Treacher, 1983). Sakul and Boylan (1992), in a study that included manysheep breeds, concluded that substantial variation for milk production exists among and within U.Ssheep breeds indicating that there may be some genetic control of this trait.

Milk score is a subjective measure of milk production of ewes that can be qualitatively determined bypalpating the ewe’s udder and observing her lambs’ fill within a few hours of lambing. Snowder et al(2001a,b) working with four breeds - Columbia, Polypay, Ramboullet and Targhee - investigated theusefulness of a subjective milk score as an alternative to directly quantifying milk yield of nursingrange ewes.

For all breeds, ewes with low milk scores gave birth to lambs with lighter birth weights than ewes withaverage or high milk scores (Snowder et al., 2001a). Birth weights of lambs born to ewes with averagemilk score were intermediate. The heaviest birth weights tended to be associated with ewes with highmilk scores. Percentage of live-born lambs reflected the same trend as birth weight and was clearlyassociated with milk score. These data suggest that that a contributing cause to higher mortality ratesamong lambs with lighter birth weights may be an association with the dam’s low milking performance.

Support for the economic importance of milk score was the strong association between ewe milk scoreand individual lamb weaning weight within each ewe age group. In all ages and breeds, ewes with highmilk scores reared heavier lambs than did ewes with low milk scores. With increasing lactations from 1to 3 years of age there was an increase in individual lamb weaning weights within all milk scoreclassifications.

Snowder et al (2001b) reported that observed heritability estimates for milk score at first parity weremoderate and similar across breeds, ranging from 0.18 to 0.32. Heritability estimates adjusted for abinomial distribution of milk scores at first parity were high (Colombia, 0.43; Polypay, 0.35;Rambouillet, 0.50; Targhee, 0.84). Estimates of observed heritability for second-parity milk score weremoderate to high, ranging from 0.23 to 0.46. Estimates of heritability for lifetime records for milk score

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ranged from 0.16 to 0.26 across breeds. Sawalha et al (2005), working with the same four breeds, foundestimates for heritability for milk score to be in the range of 0.05 to 0.18 for first, 0.01 to 0.27 forsecond, 0.05 to 0.10 for mature and 0.08 to 0.13 for all lifetime parity groups. Legarra and Ugarte(2001) reported an estimate of heritability of 0.20 for Laxta dairy sheep using 120d repeated lactationrecords. Baro et al. (1994) and El Saied et al. (1999) estimated heritability to be 0.34 and 0.18 formultiple-lactation, test-day milk yield of Spanish Churra milking sheep, respectively.

Snowder et al (2001b) found that milk score and litter weight weaned were genetically correlated at firstor second parity in Rambouillet (1.0) and Targhee breeds (1.0 and 0.61 respectively), but not in theColombia and Polypay breeds. Estimates of genetic correlations of annual lifetime milk score recordswith litter weight weaned were high (Colombia, 1.0; Polypay, 0.81, Rambouillet, 1.0; and Targhee,0.77). Sawalha et al (2005) reported genetic correlations at first parity between milk score and litterweight to be high (1.00) for Rambouillet and Polypay, and near zero for Colombia and Targhee. Atsecond parity, estimates were positive and moderate for Rambouillet and Polypay but more variable forColombia and Targhee. Although estimates are variable, the average of the estimates of the geneticcorrelation suggests that litter weight, at least in some breeds, could be improved by selecting ewes forfavourable milk score. Selection for lifetime production for litter weight weaned in Targhee ewesincreased milk yield of a 112-d lactation period by 13% compared to randomly bred control ewes (Headet al., 1995).

Milk score at first or second parity was genetically correlated with milk score records at maturity (thirdparity and greater) with estimates ranging from 0.69 to 1.00 (Snowder et al., 2001b; Sawalha et al.,2005), suggesting that additive genetic value for milking ability at maturity could be evaluated as earlyas at first parity.

Milk production of a ewe has an important effect on the preweaning survival and growth of her lambs.Experimental results suggest that selection for milk score at early parities or based on lifetime recordswould result in favourable improvement in ewe milk production and litter weight weaned. Incommercial flocks for which records for litter weight weaned are not commonly available, producersmay improve litter weight weaned by selecting and culling commercial replacement ewes based on milkscore. Even in purebred flocks where records on litter weight weaned are available, selection for milkscore may result in greater response for litter weight weaned than direct selection on this trait alone(Snowder et al, 2001a,b).

5.2 Lamb traits

5.2.1 Lamb survival

Despite its importance, lamb survival as a trait of the lamb has not been widely investigated. Moststudies investigating the trait have used a type of analysis where animals are classified as alive or deadat the end of a predetermined period (Burfening, 1993; Olivier et al., 1998; Matos et al., 2000). Theestimates of heritability of lamb survival from studies using this approach are mostly small and withinthe range of 0.00 to 0.09.

However, the use of actual survival times through survival analyses enables discrimination betweenlambs dying early or late in the period. Analysis of actual survival time also allows for the use ofrecords of lambs that were culled or died within the considered period due to reasons not related to theirviability such as slaughter or accidental death, which is relatively common under extensive productionsystems (Southey et al., 2001; Carlén et al., 2005; Sawalha et al., 2006).

Using records of Scottish Blackface lamb viability at birth4, and survival from 1-120 days, 1-14 days,15-120 days and 121-180 days, Sawalha et al. (2006) found significant differences in hazard ofmortality between gender and birth type. Female lambs had a better chance of survival during allperiods compared with males. Twin born lambs had about 50% greater hazard of mortality than singles

4 Viability at birth was defined as a binary trait (all or none) where lambs that survived for at least 24 hours afterbirth were coded with 0, and lambs born dead or that died within 24 hours of birth were coded with 1

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for the early postnatal period (1-120 days) and the hazard of mortality for triplets was about twice aslarge as that for twin born lambs for the same period. The effect of type of birth on hazard of mortalitydecreased with lamb age.

At birth, the probability of mortality was greater for triplets and singletons than for twin born lambs andgreater by 25% for males compared with females. These findings are in agreement with many otherauthors (eg Smith, 1977; Hall et al., 1995; Morris et al., 2000b; Holst et al., 2002; Christley et al., 2003;Dwyer, 2003). Birth weight has a quadratic relationship with hazard of mortality with both lighter andheavier lambs at greater risk (eg of hypothermia and dystocia respectively, among other factors).However, as mentioned above, higher birth weight lambs have a better chance of survival during theearly postnatal period. Selection for optimal rather that maximum birth weight should therefore bepracticed when lamb viability at birth and birth weight are to be improved simultaneously (Sawalha etal., 2006).

Sawalha et al. (2006) reported estimates of direct and maternal heritability in the range of 0.06 to 0.13and 0.10 to 0.14 respectively, for viability at birth and postnatal survival until weaning. These are inthe range of most reported heritability estimates in the literature for Scottish Blackface (Riggio et al.,2005) and other breeds (Fogarty, 1995; Cloete et al., 2001; Southey et al., 2001; Matika et al., 2003). Ingeneral, maternal genetic effects appear to be more important than the direct genetic effect for lambviability at birth and preweaning survival (Burfening, 1993; Morris et al., 2000b; Southey et al., 2001;Sawalha et al., 2006) although survival of lambs is clearly influenced by the genetic merit of both thelambs and the dams. It has been suggested that to achieve a higher selection gain for lamb survival,selection indices should include lamb survival as a trait of the lamb and the dam together (Sawalha,2006).

Conington et al. (2002) predicted that the inclusion of lamb survival as a trait of the lamb in a multi-traitselection index for hill sheep would increase lamb survival compared to indices with no inclusion ofthis trait (see also Conington et al., 2001). This index work has shown that by including lamb losses,lamb survival and longevity in the breeding goal, gains in productivity can be made withoutcompromising either ewe or lamb survival.

Favourable estimates of correlations between live body weights and lamb survival pre and post weaningsuggest that selection for improved postnatal survival of lambs is possible without sacrificing geneticgain in growth performance traits (Abegaz and van Wyk, 2002; Sawalha et al., 2006).

5.2.2 Gestation length

Gestation length is influenced by several factors including sire breed (Fogarty et al., 2005), dam age,litter size and litter weight at birth. Older dams have significantly longer gestation lengths (Vatankhahet al., 2000; Koyuncu et al., 2001), as do ewes carrying single lambs compared to those carryingmultiples (Osinowo et al., 1994; Vatankhah et al., 2000; Koyuncu et al., 2001; Dwyer, 2003; Fogarty etal., 2005). Gestation length increases with total litter birth weight (Knight et al., 1988; Osinowo et al.,1994; Vatankhah et al., 2000; Fogarty et al., 2005) and may be longer when the dam is carrying a malelamb compared to a female (Koyuncu et al., 2001; Vatankhah et al., 2000; Fogarty et al., 2005).

Dwyer et al. (1996), in an embryo transfer study to examine the effects of maternal and lamb genotypeon characters of the dam and progeny, found that regardless of ewe breed, gestation length was longerfor Suffolk than for Scottish Blackface lambs. This agrees with the findings of Bradford et al. (1972)that the genotype of the lamb is more important than the dam in determining gestation length. Fogertyet al (2005) reported 2-3 days variation in gestation length due to sire breed.

Few estimates of heritability for gestation length are reported in the literature but those that do existtend to be moderate to high (0.20, Osinowo et al., 1994; 0.29, Vatankhah et al., 2000). Geneticcorrelations between gestation length and litter size of -0.29 and -0.75 (Osinowo et al., 1994 andVatankhah et al., 2000 respectively) indicate that selection for a reduction in gestation length mayindirectly increase prolificacy. Osinowo et al. (1994) reported a high positive correlation (0.93)between gestation length and litter weight at birth.

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5.2.3 Parturition

The inheritance of ease of parturition is likely to be mainly maternal (Cloete et al., 2002), although thegenotype of the lamb has been shown to affect both the incidence of dystocia and assistance required atbirth (Scales et al., 2000; Fogarty et al., 2005), as well as the early post natal behaviour of the lamb(Dwyer et al., 1996; Dwyer, 2003).

Embryo transfer between Blackface and Suffolk ewes revealed that the lamb can actively contribute toits ease of delivery (Dwyer et al., 1996) with lamb characteristics such as birth weight and sex bothcontributing to the incidence of birth difficulty (Smith, 1977; Cloete et al., 2002; Dwyer, 2003). Birthweight is positively correlated with length of parturition (eg SA Mutton Merino 0.14; Dormer 0.19;Cloete et al., 2002) and ram lambs are generally heavier and have longer parturitions than ewe lambs.Likewise, singleton and triplet lambs experience more birth difficulty than twin lambs, an effect seenmore strongly in Suffolk ewes than Blackfaces (Dwyer, 2003).

5.2.4 Time taken to stand and suck

Neonate survival is dependent on the co-ordinated expression of appropriate behaviours from bothmother and young to ensure that the young is adequately fed and nurtured. In precocious species, suchas the sheep, the role of neonate behaviour in ensuring survival becomes increasingly important andmay be at least as important as that of the mother (Nowak et al., 1997; Dwyer and Lawrence, 1999a).The lamb is also an important source of sensory stimuli to the ewe to ensure that maternal behaviourcontinues to be expressed towards the lamb (Poindron et al., 1980). Although ewes will show maternalbehaviour towards stillborn lambs, their interest rapidly wanes in the absence of behavioural responsesfrom the lamb.

Lambs are born with limited tissue reserves so must suck soon after birth to survive. To sucksuccessfully, the lamb must be able to stand and show appropriate udderseeking behaviour and severalstudies have shown lamb survival is enhanced in lambs that stand and suck quickly after birth(Alexander, 1958; Owens et al., 1985; Cloete, 1993; Dwyer et al., 2001).

The time taken by lambs to stand and to suck has been examined in several breeds and exhibits somegenetic variation (Slee and Springbett, 1986; Alexander et al., 1990b; Cloete et al., 1998). In general,the lambs of lowland breeds take considerably longer than hill lambs to first stand and take longer toseek the udder. Some lowland animals, e.g. Southdown, stand relatively quickly after birth but are slowor only poorly successful in finding the udder (reviewed in Dwyer and Lawrence, 2005). Similarresponses have also been shown in mule (crossbred Blackface and Bluefaced Leicester) lambs(O’Connor and Lawrence, 1992). Extensively reared breeds are likely to experience a degree of naturalselection for lambs that both stand and suck quickly, which explains the generally good performance ofthe hill lambs. The lowland breeds have been subjected to various degrees of selection pressure andintensive husbandry practices that have kept lambs within the breeding population which may otherwisehave died.

Cloete et al (2002) estimated heritabilities for the interval from birth to standing and from standing toapparently suckling to be 0.10 and 0.08 respectively in SA Mutton Merinos and 0.22 and 0.12 inDormers. Their studies revealed that maternal effects were generally not significant for these traits butthe maternal environment to facilitate suckling, as provided by the dam, was found to play a role in theneonatal progress of lambs, in agreement with other reports (Kuchel and Lindsay, 1999; Cloete andScholtz, 1998). For example, the interval from standing to apparently suckling was shorter in a Merinoline that was selected for multiple rearing ability than in a parallel line that was divergently selectedagainst multiple rearing ability. The line difference was partially, but not wholly, accounted for by theinclusion of maternal co-operation with the first suckling attempts of the neonate in the model ofanalysis (Cloete and Scholtz, 1998).

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5.2.5 Ewe recognition and attachment

Sheep are a ‘follower’ species (Lent, 1974), thus the lamb needs to keep up with its dam soon afterbirth. This requires that the lamb not only shows appropriate locomotor competence, but that it candiscriminate its own dam from other ewes and is attracted to remain with her. Studies in Merinossuggested that separation between ewe and lamb was a major contributory factor to lamb mortality(Stevens et al., 1982; Alexander et al., 1983).

Data from Merino and Blackface crossbred animals compared to purebreds suggest that lamb factorsare implicated in ewe–lamb separation (Stevens et al., 1984; O’Connor and Lawrence, 1992). Inspecific tests, singleton Merino lambs that were able to recognise their mothers 12 h after birth hadbetter survival than lambs that could not (Nowak and Lindsay, 1992). Thus, recognition of its motherand attraction to her are important lamb behaviour traits for survival.

Lambs are initially attracted to any large objects, but can recognise their mothers at close quarters asearly as 12 h after birth (Nowak et al., 1987), and at a distance by 24 h old (Shillito and Alexander,1975; Nowak, 1991). Their discriminative ability allows them to avoid potentially aggressive aliendams and to maintain close contact with their own nursing mothers (Nowak et al., 2000). In lambs,both visual and auditory cues are involved in mother discrimination whether at close contact or at adistance (Nowak, 1991). Ewes and lambs answer each other’s bleats and respond to the recordedvocalisations of their partners (Shillito-Walser et al., 1981; Shillito-Walser et al., 1982) suggesting thatthe behaviour of both ewe and lamb may play an important role in the ability of the lamb to recogniseits dam (Nowak, 1991;Terrazas et al., 2002).

Breed comparisons have shown that, in general, extensively bred hill lambs (Dalesbred, ScottishBlackface) are better at ewe recognition than the more intensively managed lowland breeds (ClunForest, Suffolk; Shillito-Walser, 1980; Pickup, 2003). However, whether this is due to betterdiscriminatory capabilities of the lambs or to maternal behaviour characteristics, particularly ewe vocalbehaviour (Terrazas et al., 2002), is not clear.

Lamb recognition of the ewe is related to lamb sucking activity and colostrum ingestion (Nowak et al.,1997; Goursaud and Nowak, 1999). The post-ingestive internal state is believed to enhance awarenessof the characteristics of the maternal body, or facilitate the integration of different cues used fororientation and reunion with the dam. Thus, differences between breeds may also be related to thequality of sucking interactions.

5.2.6 Cold resistance

Cold resistance as an indicator of exposure is another important determinant of lamb survival in manyenvironments. Although sheep are particularly resistant to cold weather, and even new-born lambs areable to maintain body temperature in air temperatures of well below freezing provided the lamb is dry(McCutcheon et al., 1983), hypothermia of wet neonatal lambs may account for nearly half of allperinatal deaths (Houston and Maddox, 1974). Hypothermia also causes a decrease in lamb suckingactivity (Alexander and Williams, 1966), so accelerating death from starvation as the limited reserves ofthe neonate lamb are rapidly diminished.

Breed differences in mean rectal temperatures of lambs when measured 1 h after birth show that there isconsiderable variation in the ability of lambs to maintain homeothermy after birth (Sykes et al., 1976;Samson and Slee, 1981; Slee and Springbett, 1986; Dwyer, 2002). In general, the hill and feral breedsof lamb maintained higher rectal temperatures over the first hour of postnatal life than the lowlandbreeds. When adjusted for differences in body weight, hill and feral breeds had the highest weightspecific cold resistance (Samson and Slee, 1981).

Experiments with cold resistance using water bath tests have reported heritability estimates of 0.3 (Sleeand Stott, 1986); 0.36 (Wolff et al., 1987) and 0.7 (Slee el al., 1991). Slee and Stott (1986) reported arealised heritability of 0.27 for increased cold resistance but a realised heritability of zero for decreased

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cold resistance. In addition, a major gene associated with cold resistance has been identified (Slee andSimpson, 1991; Simpson & Slee, 1998).

Breed differences in maternal factors, such as maternal grooming behaviour, might contribute to thelamb’s ability to maintain temperature. However, an un-published comparison of rectal temperatures ofSuffolk x Blackface lambs with pure Suffolk lambs (where there was no difference in maternalgrooming behaviour by the Suffolk dams) suggests that these differences are predominantly due to thegenetics of the lamb (median rectal temperatures (8C) of crossbred lambs = 39.9, Suffolk lambs = 39.2,P < 0.001; cited in Dwyer & Lawrence, 2005). As discussed above for neonatal lamb behaviours,intensive management strategies may help to keep lambs with poor cold resistance within the breedingpopulation when they may have died under more extensive management.

Birth coat depth and skin thickness both show significant genetic correlations with cold resistance (Sleeet al., 1991), suggesting they are important components of the maintenance of homeothermy in lambsby providing insulation. Skin thickness and coat depth are greatest in the hill breeds in comparison tolowland breeds, probably due to natural selection for improved cold resistance in the latter (Samson andSlee, 1981).

Although birth coat and body weight differences play a role in cold resistance, significant breeddifferences still remain once these components have been accounted for (Samson and Slee, 1981). Thisdifference is presumably related to the ability of different breeds to generate endogenous heat.Research indicates that the lowland intensively managed breeds have a lower ability to generate heatthrough non-shivering thermogenesis compared to hill breeds (reviewed in Dwyer & Lawrence, 2005).

The composition of maternal colostrum also contributes to the available lipids for neonatal metabolism.Although variation in lamb intake probably contributes most to variation in colostral energy supply,unpublished data show that colostrum from Blackface ewes contains a relatively greater percentage oflipid than that of Suffolk ewes, thus Suffolk lambs may struggle to obtain sufficient energy to maintainhomeothermy both from their reduced sucking ability and the lower level of lipid in the colostrum theyingest when compared to hill lambs (Dwyer & Lawrence, 2005).

6 Breeding for other traits

6.1 Tolerance to food shortages

Webster (1993) suggests that selection should include traits which increase tolerance to long termconsequences of prolonged food shortage; not just shortage of energy, but also of N, phosphorus,copper and selenium. Woolliams et al. (1986) showed that lambs from two genetic lines selected forlow or high copper status differed substantially in mortality and resistance to infection.

Differences in grazing behaviour between and within breeds may indicate that breeds or individualswithin breeds are better adapted to extensive conditions. There are reports of differences between sheepbreeds in the time spent grazing. For example, of six breeds studied by Dudzinski and Arnold (1979)Suffolks had the longest grazing times, followed by Border Leicester, Dorset Horn and Romney sheep,whilst Cheviot and Southdown sheep had the shortest grazing times. In a study of Merino ewes, theindividuals with the longer grazing times ended the morning bout later and started the afternoon boutearlier than those individuals with the shorter grazing times (Arnold and Dudzinski, 1978). Similarly,Cheviot and Suffolk sheep commenced grazing earlier in both the morning and the afternoon thanDorset Horn, Southdown and Border Leicester sheep. Romney sheep started grazing later in both themorning and afternoon, but also finished both bouts later (Arnold and Dudzinski, 1978). It is thoughtthat the differences in grazing times are mainly accounted for by increased grazing activity during thegrazing bouts.

Certain breeds of sheep which live on hill land, such as the Scottish Blackface and Cheviot sheep, formhome ranges, where the daily patterns of movement, at least initially, are learned from the precedinggeneration (Lawrence and Wood-Gush, 1988; Lynch et al., 1992). Other breeds, such as the Merino, donot establish home ranges, possibly because the same area of land is not used by successive generations.

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The distance walked by sheep in a day also varies with breed. Cheviot sheep have been shown to walkfurther than Romney sheep on both flat and hill land, although the difference between the two breedswas greater on the hill pasture. Distances walked by individual sheep were similar in successive weeks(Cresswell, 1960). The topography of the land, type of vegetation and frequency of drinking will allaffect the distance travelled.

The distance between grazing animals can vary from 4 m for Merinos to 19 m for the British hill breeds(Arnold and Dudzinski, 1978). Kilgour et al. (1975) found that some sheep, Dorset-Romneys inparticular, did not disperse even when herbage availability was very low, whilst Merino sheep havebeen reported to disperse only under such conditions (Fraser and Broom, 1990). It is thought that breedswhich remain close together may not be suited to areas where favoured herbage patches are somedistance apart (Hunter, 1960), such as in extensive grazing systems.

Provided that sheep are given sufficient area and choice, they will be selective in their diet (Hafez,1975; Fraser and Broom, 1990). Sheep may select between different plant species, individual plants,and parts of the plants available (Lynch et al., 1992). However, there is considerable variation betweenindividuals of the same breed (Arnold, 1981; Lynch et al., 1992). Arnold (1981) showed that sheepfrom the Australian rangelands preferred different pasture plants to sheep kept on sown pastures, andthat differences are strongly influenced by the previous nutritional history of the animal.

Similarly, Key and MacIver (1980) found that when Clun Forest lambs were cross-fostered on to WelshMountain ewes they preferred the tussock and heather vegetation eaten by the ewes, whilst WelshMountain lambs fostered on to Clun Forest ewes preferred the improved pastures grazed by their fostermothers.

In future, more emphasis on research on within breed genetic variation in grazing behaviour, andassociations with production and animal welfare would be valuable in helping to formulate breedinggoals for extensive systems.

6.2 Longevity

Improving ewe longevity has been documented as being important for livestock profitability(Conington et al., 2001) and evaluations of this trait are currently used in breeding programmes in theUK for dairy cows (Veerkamp et al., 1995; Brotherstone et al., 1997).

However estimates for heritability of longevity (defined as days or years in the flock) are low (0.06 forAustralian Dorset sheep, Brash et al.,1994c; 0.08 for Scottish Blackface, Conington et al., 2001),suggesting that only moderate gains could be made from selection on this trait.

Brash et al. (1994c) reported negative genetic correlations between longevity and number of lambsborn/ewe joined (-0.15), litter size (-0.23) and lamb survival (-1.0). The same authors found longevityto be positively correlated with ewe fertility (ewes lambing/ewe joined; 0.29) and negatively correlatedwith number of lambs weaned per ewe joined (-0.11). In contrast, Conington et al. (2001) reported apositive correlation between longevity and number of lambs reared (0.35). Conington et al. (2001) alsoreported positive genetic correlations between longevity and mature size (0.24), fleece weight (0.26),average weaning weight (0.21), fat depth (0.20) and muscle depth (0.31). They reported a moderatenegative correlation between number of lambs lost and longevity (-0.35).

Conington et al. (2001) suggest that improving the longevity of the flock within the context of a multi-trait selection index should ensure that higher flock productivity will not be achieved at the expense ofshorter ewe lifespan. Recording ewe longevity in breed improvement programmes is inexpensiverelative to the benefits gained through genetic improvement.

Longevity in rams is important for commercial lamb producers but is less important in pedigree flocksand studs where rapid replacement of both rams and ewes will reduce the generation interval andenhance the rate of genetic progress while limiting the accumulation of inbreeding (Brash et al., 1994c).

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6.2.1 Teeth and bone

Good bone quality in breeding ewes is important for the mineralisation of foetal skeletons and to sustainmaternal dentition, as tooth loss is one of the main reasons for culling sheep in the UK (Herrtage et al.,1974; Aitchison and Spence, 1984). Among other functions, bone is a storage depot for calcium andother key minerals that are mobilised to meet major demands such as during lactation.

As studies in humans and poultry have shown, there is substantial genetic variation for bone properties(h2 between 0.5 and 0.8), suggesting a similar situation in ewes. These properties, e.g. bone density, arekey to successful production and nurturing of healthy lambs, which can be used in selective breedingstrategies to extend breeding ewes’ productive lives.

CT has been shown to be a useful method of assessing bone properties in sheep (Rubin et al., 2001).Conington et al (2004) using CT to quantify the main bone types in Scottish Blackface ewes andinvestigate environmental factors affecting bone quality found that bone depletion followed a similarpattern to that of fat and muscle between mating and pre-tupping (Lambe et al., 2003). Age of dam andheft were not key factors affecting bone properties but the cumulative number of lambs born was. Boneproperties showed weak relationships with body composition or live weight. Variation between sireprogeny groups indicated that there is a significant genetic component to bone properties.

More data are required to allow the estimation of genetic parameters for bone mobilisation and bonecharacteristics, and to assess further the key factors affecting bone properties Conington et al. (2004).

6.3 Body composition

The ability of the ewe to maintain her own body composition throughout the reproductive cycle is animportant component for the economic efficiency of the flock. The use of CT in the prediction ofinternal and carcass fat levels in hill ewes has shown that the depletion and repletion of fat and musclein these depots is under genetic control (Lambe et al., 2005). The use of this information to selectanimals that are better able to withstand harsh environmental conditions, yet produce and rear theirlambs with no supplementary feeding, should be an important goal for easy-care sheep breedingsystems. Current research at SAC is investigating the incorporation of this trait into new selectionindices for the hill sheep sector (J. Conington, pers. comm.).

6.4 Wool shedding

It has long been recognised that feral and certain breeds of sheep, such as the Wiltshire Horn, tend toshed their own wool, reducing the need for shepherding tasks such as shearing and dagging (Tierney,1978; Rathie et al., 1994). Wool shedding also makes these breeds considerably less susceptible toblowfly strike of the breech and prepuce region than non-wool shedding breeds and crosses (Tierney,1978; Litherland et al., 1992; see section 2.4 of this report). Environmental factors such as stress and illhealth cause premature wool loss in many breeds although the degree to which fleece loss occurs insome breeds (e.g. North Country Cheviot) is under genetic control (Conington et al., 1990).

It has been suggested that in the UK, sheep have more wool than they need, as they need very littledepth for insulation. Winter shearing of inwintered lambs reduces heat stress and therefore respirationrate and increases the gestation length of ewes, resulting in heavier lambs at birth. Ewe lambs shornbefore mating produce 15% more lambs. Prior to summer shearing ewes are slow to move and grazeless actively (Vipond, 2006).

The Easycare breed developed by Iolo Owen was derived from the Nelson Welsh Mountain (WelshMountain x Cheviot) which were crossed twice to the Wiltshire Horn, a wool shedding breed, andselected for wool shedding, no horns and easy care traits. Easycares carry a reasonable fleece of up to 1- 2 inches in length through the winter which they cast in the spring. Typically they are not housed andare fed minimum amounts of concentrates. Where there is no threat from sheep scab, no dipping isrequired as there is a substantially reduced risk of blowfly on non-soiled parts of the wool.

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Lambs at birth appear to have sufficient wool and, being a leggy breed, quickly get to their feet and startsuckling. The breed has the potential to significantly reduce labour input and is recommended whereshearing is expensive and difficult to organise (Vipond, 2006). From observation, it is clear that there isa major gene influencing the fleece shedding in the Easycare breed and it would therefore be an idealcandidate for QTL studies.

6.5 Temperament

The adoption of extensive rearing systems will involve profound changes in animal husbandry. Certainenvironmental factors or animal characteristics that were previously of little importance may emerge asobstacles to the successful implementation of extensive management or prove to be prejudicial toanimal welfare. Of these different factors, animal-human relationships are of prime importance (LeNeindre et al, 1996).

Studies performed on extensively farmed animals have indicated that behavioural response to humans(or ‘temperament’, defined as the manner in which individuals react to novel or challenging situations;Mason, 1984; Wilson et al., 1994) affects production. It has been shown to influence reproductiveperformance in heifers, for example, in which ‘emotional’ females have more silent ovulations(ovulation without sexual behaviour) than ‘unemotional females’ (Gauthier and Thimonier, 1982). Incattle reared under extensive conditions, reaction to handling seems to determine, at least in part, theincidence of bruising at the slaughter house (Fordyce et al., 1985). In sheep, Murphy et al (1998) andO’Connor et al. (1985) have shown that ‘calm’ ewes exhibit better maternal behaviour after parturitionthan ‘nervous’ ewes, affecting lamb survival (see section 4.1.3 of this report). Gelez et al (2003) foundthat temperament affects ewe sexual behaviour. Calm ewes were more proceptive5 than nervous onesand tended to be more receptive6 to the ram. In bighorn sheep, Réale et al. (2000) observed that ‘bold’ewes started reproducing earlier and had a significantly higher weaning success than ‘shy’ ewes.

The reaction of animals to human presence depends on their previous experience and their geneticcharacteristics (Le Neindre et al., 1996).

Murphy et al., (1994) established a method for assessment of temperament by combining twobehavioural tests: (1) the ‘arena test’, a motivational choice test that measures the approach andavoidance behaviour of sheep, similar to tests used to measure reactivity in cattle (Fell et al., 1999).;and (2) the ‘box test’, similar to an isolation test used in sheep and cattle to measure the degree ofanxiety (Cockram et al., 1994; Burrow, 1997). For sheep, the heritability of these temperamentparameters is around 0.23 and the repeatability from weaning to 3-year old ranges from 0.54 to 0.82(Martin et al., 2004). For over 10 years, researchers in Australia have used these measures to select twoexperimental lines of sheep, a ‘calm’ line and a ‘nervous’ line, to create the ‘Allandale Flock’ that isnow used to study the relationship between temperament and production characters (Martin et al.,2004).

The main outcome has been a clear demonstration that calm ewes are better mothers than nervous ewes(Murphy et al., 1994). The calm ewes spend more time with their lambs, have a shorter flight distancewhen disturbed and return to their lambs faster than nervous ewes. Consequently, lamb mortality frombirth to weaning for calm ewes was about half that of nervous ewes. The poor mothering ability of thenervous ewes was the main factor associated with lamb mortality.

Effectively, the selection process produces animals that show less intense stress responses as theyinteract with their environment. In addition to postnatal lamb survival, stress disrupts many otheraspects of the reproductive process, all of which might be improved by genetic selection for ‘calmtemperament’. These include the length of the oestrous cycle (Braden and Moule, 1964; Przekop et al.,1984), ovulation rate (Doney et al., 1976), the proportion of ewes mated (McMillan and Knight, 1982),embryo survival (Van Niekerk et al., 1968) and sexual behaviour (Gelez et al., 2003). Finally, in otherspecies, temperament seems to improve other aspects of production such as growth rate (Voisinet et al.,

5 Proceptivity = time spent in close contact with males6 Receptivity = percentage of immobilizations in response to nudges by the male

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1997; Burrow, 1998; Fell et al., 1999), immune function (Fell et al., 1999), milk yield (Lawstuen et al.,1988) and meat quality (Jones and Hocking, 1999; Reverter et al., 2003). All of these outcomes wouldimprove productivity without compromising animal welfare or ethics.

Sheep Genetics Australia is planning to offer Australian Sheep Breeding Values for temperament in thenear future to Lambplan and Merinoselect customers.

7 Conclusions

7.1 Breeding for resistance to disease

7.1.1 Nematodes

Genetic variation in many aspects of host resistance to nematodes is well documented. Including GIparasite resistance in breeding goals may benefit sheep production enterprises in a number of ways, forexample, (i) direct increases in productivity resulting from favourable genetic correlations betweenresistance and performance, (ii) decreased pasture contamination, leading indirectly to improvedperformance, (iii) decreased treatment costs and (iv) less tangible benefits such as improved health andwelfare (Bishop et al., 2004). The genetic correlation between resistance and performance willinfluence the nature of the benefits of improving resistance. As the correlation becomes progressivelyless favourable, the benefits will change from direct improvements in productivity to less easilyquantifiable benefits via decreased pasture contamination, improved health and welfare, and decreasedtreatment costs.

If selective breeding for nematode resistance is to be implemented then it is necessary to be able toquantify host susceptibility or resistance to infection. Faecal egg count (FEC) is the indicator traitcommonly used and the exploitation of host genetic variation in resistance using FEC in commercialsheep breeding programmes is now well-established in New Zealand and Australia (Morris et al., 1997,2000b; Woolaston and Piper, 1996; Woolaston and Windon, 2001), leading to reduced dependency ondrug usage. Studies have also demonstrated that it would be feasible, in principle, to use FEC to selectsheep for resistance to gastrointestinal nematode parasites under typical commercial sheep conditions inthe UK where sheep face a natural parasite challenge (Bishop et al., 1996; Bishop et al., 2004).

However, the use of FEC as the only indicator trait is time-consuming and costly. Traits other than FECmay be used to assess resistance to nematodes or host response to infection:• Dag score and faecal consistency score have a poor relationship with faecal egg count implying that

they would be ineffective to improve host resistance to parasites.• Selection for increased IgA activity and eosinophil count might be useful to decrease worm

development and fecundity.• Families with high fructosamine concentration have long, fecund worms and therefore it may be

possible to use fructosamine concentration to indicate infection status.• There has been some success in QTL detection, but generally the number of significant QTL

reported is probably less than expected given the degree of international research effort into thisarea. Current research aims to fine map QTL, for example using dense SNP markers, and to studythe functional significance of genes that may underlie host responses to infection. Early resultssuggest that microarray studies do have the ability to detect genes differentially expressed between'resistant' and 'susceptible' sheep, with pathways implicated in these differences including thedevelopment of acquired resistance and the structure of the intestinal smooth muscle (Diez-Tascón etal., 2005).

7.1.2 Footrot

Although selection of sheep with enhanced resistance to the disease using footrot lesion scoring(appendix 8.1) has been shown to be successful (Skerman, 1985; Skerman and Moorhouse, 1987;Patterson and Patterson, 1989), genetic markers potentially offer a practical alternative to laboriousscoring and protocols that require exposure to infection.

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A footrot gene-marker test is now commercially available in New Zealand (Hickford, 2000). Recentsurvey results indicate that on properties that have adopted the technology, the use of chemicalsolutions to control the disease have been substantially reduced, as have the number of doses of vaccineand antibiotics. Overall, footrot prevention and control costs have been reduced by between 50 and70% (Greer, 2005).

While it is possible that the NZ information will be relevant to sheep populations in the UK, theassociations among the molecular genetic markers, footrot resistance and footrot-causing bacteriastrains need to be demonstrated in UK sheep populations. Together with phenotypic data describingfootrot severity and additional information contributed from the exploration of other parts of the MajorHistocompatibility Complex region, it would then be possible to determine whether or not breeding forenhanced footrot resistance using molecular markers could be a practical and feasible option for the UKsheep industry.

7.1.3 Mastitis

Unexpectedly from its economic impact there is a dearth of information about the genetics, incidenceand economic consequences of mastitis in meat sheep breeds, and the potential to include mastitisresistance in meat sheep breeding programmes. Therefore the majority of all relevant literature reportedis on dairy cattle, with some on dairy sheep. The implications of this are that fundamental research onmastitis in meat sheep breeds is urgently required. This needs to be done at the population level tounderstand the major contributing factors to mastitis, the timing, prevalence and ultimately genetics ofthe disease. This is important knowledge when choosing the right model for genetic evaluations formastitis resistance and will enable the development of robust recording protocols so that unbiased andobjective records of familial susceptibility to mastitis can be understood, and appropriate breedingprogrammes instigated to breed mastitis-resistant sheep.

Selection for resistance to mastitis in dairy sheep is currently underway in the French breed Lacauneusing SCC as a proxy trait for mastitis and incorporating it into sheep dairy breeding programmes(Rupp et al., 2002). However, the continuous measurement of phenotypic indicator traits for mastitisresistance is time and labour intensive, and the future use of suitable molecular genetic markers couldbe an attractive proposition, particularly for meat sheep breeds as it does not require milk sampling.More research is needed in this area.

7.1.4 Blowfly strike

Blowfly strike is an important disease of sheep, causing the deaths of an estimated 12,000 animals eachyear in the UK (Sargison, 2004). Clipped sheep and young lambs with short fleeces are not usuallyattacked, but as the length of the fleece increases so does the risk of strike (French et al., 1996).

Differences exist both between and within breeds in susceptibility to fly strike indicating that thepredisposition of sheep to flystrike is in part genetically determined, with potential scope for within-flock genetic improvement.An alternative approach to the problem is to introduce new genetic material into the population in anendeavour to make sheep less susceptible to blowfly strike. Of interest in this respect is the WiltshireHorn breed in which fleece wool is shed annually (Slee and Carter, 1961, 1962; Ryder, 1969).

7.2 Breeding for enhanced flock fertility

7.2.1 Ewe prolificacy

Many studies indicate that an increase in ewe prolificacy could potentially be achieved through geneticselection on litter size, ovulation rate or ram scrotal circumference, or a combination of the three.However, increasing litter size may also contribute to an increase in lamb mortality, particularly in moreextensive systems, i.e. the optimum is not necessarily the maximum achievable. A target mean valueappropriate to the particular management system, feed resources and lambing season for the flock(s) inquestion should be set before a selection programme is initiated. Optimum litter size at birth is

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influenced by survival rates of singles, twins and higher multiples, and by the growth rate of survivorsin a specific set of management conditions.

Conington et al. (2001) suggest that, particularly in extensive systems, it is more cost effective to farmewes with the ability to rear more of their lambs (see sections 4 and 6.3 of this report), rather thanincreasing prolificacy per se. This is partly because of the costs involved in supplementary feedingewes that are carrying higher litter sizes during winter. This is in agreement with the findings reportedby Ercanbrack and Knight (1998) and Snowder (2002) that selecting directly for total weight of lambweaned per ewe rather than litter size or fertility will lead to more improvement. Total litter weightweaned represents a ‘biological index’ which incorporates variation in fertility, litter size, viability andgrowth rate, and no doubt other components not normally recorded such as ewe lamb-rearing ability(Bradford, 2002).

In the U.S., Australia and New Zealand, litter size born is currently genetically evaluated.

7.2.2 Scrotal circumference

Scrotal circumference may be a useful indirect selection criterion for improvement of femalereproduction. Although results are variable, testis size appears to have a positive relationship withovulation rate and possibly also litter size (Matos and Thomas, 1992). The use of rams with largertestis measurements may allow a reduction in the number of rams required for breeding each year andincrease the overall reproductive efficiency of the flock (Duguma et al., 2002).

However, although various reports indicate that scrotal circumference is moderately to stronglypositively correlated with liveweight at different ages (Brash et al., 1994a,b; Fossceco and Notter, 1995;Al-Shorepy and Notter, 1996; Duguma et al., 2002), others have reported a negative correlationbetween the two traits (Land, 1982; Burfening and Davis, 1998; Haley et al., 1990) raising doubts aboutthe value of including information on scrotal circumference in a selection programme to improve littersize.

If selection for testicular size is to be practiced, scrotal circumference growth from 90 to 180d (withsome adjustment for liveweight) appears to be the trait of choice because it generally has the highestheritability (Matos et al., 1992; Fossceco & Notter, 1995; Al-Shorepy & Notter, 1996).

Sheep Genetics Australia currently offers breeders Australian Sheep Breeding Values for scrotalcircumference at post-weaning, yearling and hogget ages.

7.2.3 Ram serving capacity

Response to selection for serving capacity should be favourable, with selection resulting in ramscapable of mating with more ewes, improving the reproductive efficiency of the flock and reducing thenumber of rams needed. Tests for serving capacity7 have been shown to accurately predict the breedingperformance of high and low performance rams (Ibarra et al., 2000; Snowder et al., 2002; Stellflug etal., 2006) and can identify rams with high sexual performance at an early age (14 months; Snowder etal., 2002).

Sire sexual performance influences the proportion of high to low performing ram lambs produced, withsons born to high-performing sires attaining a significantly higher number of ejaculations than sonsborn to low performing sires (Bench et al., 2001). Furthermore, daughters of high performing sires aresignificantly younger at first behavioural oestrus than daughters of low performing sires (Bench et al.,2001). However, the general trend for low genetic correlations between sexual performance of ramsand ewe reproductive traits suggests that breeding rams with high sexual performance will have little, ifany, positive effect on genetic improvement of number of lambs born or number of lambs weaned.Direct selection on the ewe is therefore likely to be more effective for improving lamb production(Snowder et al., 2004).

7 Serving capacity tests assess the rate at which rams attain successful matings when housed with oestrous females

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Rams with highly desirable production traits and high serving capacity will leave more offspring forfuture generations compared to rams with similar desirable production traits but a low serving capacity,thus increasing the rate of genetic improvement for both serving capacity and production traits(Snowder et al., 2002).

7.3 Breeding for enhanced maternal ability and lamb survival

Lamb mortality is a major constraint to efficient sheep production (Alexander, 1988; Haughey, 1991)with the vast majority of lamb deaths occurring within 1-3 days of birth (Nowack et al, 2000; Southeyet al., 2004). High lamb mortality could be reduced substantially by a short period of labour and bymaternal behaviours which protect the nutritional and thermal state of the lambs (Alexander, 1988;O’Connor and Lawrence, 1992). This is particularly important in more extensive management systemswhere ewes must be able to conceive, carry, give birth to and rear their young with little (orsubstantially reduced) human intervention.

In general, maternal genetic effects appear to be more important than the direct genetic effect for lambviability at birth and preweaning survival (Burfening, 1993; Morris et al., 2000b; Southey et al., 2001;Sawalha et al., 2006), although survival of lambs is clearly influenced by the genetic merit of both thelambs and the dams. Selective breeding has been advocated as a means of improving lamb survival andewe rearing ability within breeds, despite the low heritability of these traits.

Conington et al. (2001, 2002) predict that using multi-trait selection indexes, improvements in maternalcharacteristics can be achieved alongside increasing lamb weaning and carcase weights. Key potentialindex traits include lamb loss from birth to weaning, litter size at weaning and average weight of lambsweaned. ). Including lamb survival as a trait of the lamb as well as lamb losses in the index is predictedto reduce lamb ‘wastage’ between birth and weaning (Conington et al., 2002).

The U.S. National Sheep Improvement Programme uses weight of lamb weaned per ewe exposed over agiven time interval as an indicator of ewe production efficiency. This is a complex trait that includesfertility, prolificacy, maternal ability, lamb survival, and growth and is calculated only for ewes thatwean at least one lamb (Wilson and Morrical., 1991; Notter, 1998).

Maternal ability traits• An important component of ease of delivery is the pelvic dimension of the ewe. Ewes selected for

lamb-rearing ability have increased pelvic dimensions and therefore experience fewer lambingdifficulties (Kilgour and Haughey, 1993). CT scanning may prove to be a useful way to measurepelvic capacity in ewes to aid selection for lambing ease but larger trials are necessary to quantifygenetic properties of dystocia and pelvic measurements and their relationship with other productiontraits before selective breeding for large pelvic capacity can be recommended (Bilbe et al., 2005).

• Ewe behaviour around lambing time has a large effect on lamb survival, particularly in extensivesystems (Nowak, 1996).o Isolation from the rest of the flock during and after parturition is an important preliminary step

in the formation of the mother-young bond. Ewes selected for lamb-rearing ability tend toremain longer on or near their birth sites than control line contemporaries (Knight et al., 1989).

o The ewe forms a memory for her own lambs that allows her to restrict maternal careexclusively to her own offspring (Poindron et al., 1984a). Lowland ewe breeds managedintensively tend to show poorer maternal care at birth than breeds managed more extensivelysuggesting a relaxation of selection pressure in intensive systems such that variation in maternalcare has less influence on the survival of the lamb (Dwyer and Lawrence, 2005).

o Maternal co-operation shortens the interval from standing to apparently suckling. Ewesselected for rearing ability are less likely to circle and back than control line ewes and are morelikely to adopt a posture to facilitate suckling (Cloete and Scholtz, 1998).

• Maternal Behaviour Score, based on the proximity of the ewe to her lamb as it is handled, (appendix8.3) may be a useful tool to measure maternal behaviour. The score has been shown to be related toboth postnatal lamb survival and weaning weight (O’Connor et al., 1985; O’Connor, 1996; Lambe et

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al., 2001; Everett-Hinks et al., 2005; Sawalha et al., 2006). The score may reflect the ewes’underlying temperament as much as it measures their maternal behaviours (Dwyer and Lawrence,2005).

• Increased milk production of range ewes is associated with increased lamb survival and growth(Torres-Hernandez and Hohenboken, 1980). Selection on Milk Score8 at early parities or based onlifetime records may result in favourable improvements in ewe milk production and litter weightweaned (Snowder et al., 2001 a,b).

Lamb traits• Birth weight has a quadratic relationship with hazard of mortality with both lighter and heavier

lambs at greater risk (eg Smith, 1977; Hall et al., 1995; Morris et al., 2000b; Holst et al., 2002;Christle et al., 2003; Dwyer, 2003). Selection for optimal rather than maximum birth weight shouldtherefore be practiced (Sawalha et al., 2006).

• Favourable estimates of correlations between live body weights and lamb survival pre and postweaning suggest that selection for improved postnatal survival of lambs is possible withoutsacrificing genetic gain in growth performance traits (Abagaz and van Wyk, 2002; Sawalha et al.,2006).

• The inclusion of lamb survival as a trait of the lamb in a multi-trait selection index for hill sheepwould increase lamb survival compared to indices with no inclusion of this trait (Conington et al.,2002). To achieve a higher selection gain for lamb survival, selection indices should include lambsurvival as a trait of the lamb and the dam together (Sawalha et al., 2006).

• The genotype of the lamb is more important than the dam in determining gestation length (Bradfordet al., 1972; Dwyer et al., 1996). Selection for a reduction in gestation length may indirectlyincrease prolificacy (Osinowoet al., 1994; Vatankhah et al., 2000).

• The inheritance of ease of parturition is likely to be mainly maternal (Cloete et al., 2002), althoughlamb characteristics such as genotype, birth weight, sex and birth type (singles/multiples) have beenshown to affect the incidence of dystocia (Scales et al., 2000; Fogarty et al., 2005; Cloete et al.,2002), as well as the early post natal behaviour of the lamb (Dwyer et al., 1996; Dwyer, 2003).

• The time taken by lambs to stand and suck exhibits some genetic variation (Alexander et al., 1990b;Cloete et al., 1998) and therefore could be a possible candidate trait for inclusion in a selectionprogramme.

• Recognition of its mother and attraction to her are important lamb behaviour traits for survival(Nowak and Lindsay, 1992). Both visual and auditory cues are involved (Nowack, 1991) as well assucking activity and colostrum ingestion (Goursaud and Nowak, 1999).

• Breed differences in mean rectal temperatures of lambs show that there is considerable variation inthe ability of lambs to maintain homeothermy after birth (Samson and Slee, 1981; Dwyer, 2002).Birth coat depth and skin thickness are also correlated with cold resistance (Slee et al., 1991).

7.4 Breeding for other traits

It has been suggested that selection should include traits which increase tolerance to long term foodshortage (Webster, 1993). More research on within breed genetic variation in grazing behaviour andassociations with production and animal welfare would be valuable in helping to formulate breedinggoals for extensive systems.

8 Milk score is a subjective measure of milk production of ewes that can be qualitatively determined by palpatingthe ewe’s udder and observing her lambs’ fill within a few hours of lambing (Snowder et al., 2001a,b).

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Improving ewe longevity has been documented as being important for livestock profitability and,despite its low heritability, inclusion of the trait in a multi-trait selection index should ensure that higherflock productivity will not be achieved at the expense of shorter ewe lifespan (Conington et al., 2001).Recording ewe longevity in breed improvement programmes is inexpensive relative to the benefitsgained through genetic improvement.

Good bone quality in breeding ewes is important for the mineralization of foetal skeletons and tosustain maternal dentition. CT has been shown to be a useful method of assessing bone properties insheep (Conington et al., 2004) but more data are required to allow the estimation of genetic parametersfor bone characteristics.

The ability of the ewe to maintain her own body composition throughout the reproductive cycle is animportant component for the economic efficiency of the flock. The use of CT in the prediction ofinternal and carcass fat levels in hill ewes has shown that the depletion and repletion of fat and musclein these depots is under genetic control (Lambe et al., 2005). The use of this information to selectanimals that are better able to withstand harsh environmental conditions, yet produce and rear theirlambs with no supplementary feeding, should be an important goal for easy-care sheep breedingsystems. Current research at SAC is investigating the incorporation of this trait into new selectionindices for the hill sheep sector (J. Conington, pers. comm.).

Selection for wool shedding may result in sheep requiring less shepherding input (e.g. shearing anddagging) and that are less susceptible to blowfly strike (Tierney, 1978; Rathie et al., 1994). More dataare required to allow the estimation of genetic parameters for this trait.

Selection for animals with a calm temperament produces animals that show less intense stress responsesas they interact with their environment, including stockpeople (Martin et al., 2004). This could result inimprovements in postnatal lamb survival and many other aspects of reproductive and productiveefficiency. Behavioural tests have been developed which allow the effective assessment oftemperament (Murphy et al., 1994).9 Sheep Genetics Australia is planning to offer Australian SheepBreeding Values for temperament in the near future to Lambplan and Merinoselect customers.

7.5 Application to the UK sheep industry

Some of the traits included in the report are already used in UK sheep breeding schemes (e.g. ewelongevity is predicted in breeding programmes for hill sheep although it is not recorded separately inpractice). Other traits are in the pipeline to be included in breeding programmes (e.g. direct lambsurvival) and others are still being researched (e.g. resistance to footrot, nematodes and mastitis).

Difficulties that may be encountered when trying to incorporate some of the traits into breedingprogrammes include:

• insufficient evidence for genetic variation in the trait concerned (e.g. bone quality);• insufficient consensus or knowledge about the ‘best’ trait to be recorded to achieve the breeding

goal (e.g. resistance to nematodes);• traits that are difficult, time-consuming or expensive to record (e.g. behavioural traits);• the fact that ‘hidden’ benefits of trait improvement may not immediately appeal to some breeders

because their cumulative benefits are not realised until some time in the future (e.g. longevity).

However, most of the traits reviewed could potentially be used in UK sheep breeding programmes. Theuse of genetic information from related animals would be particularly useful where the heritability ofthe traits is low or if they are difficult to record.

9 Behavioural tests for the assessment of temperament in sheep include: (1) the ‘arena test’, a motivational choicetest that measures the approach and avoidance behaviour of sheep, similar to tests used to measure reactivity incattle (Fell et al., 1999).; and (2) the ‘box test’, similar to an isolation test used in sheep and cattle to measure thedegree of anxiety (Cockram et al., 1994; Burrow, 1997); or a combination of the two (Murphy at al., 1994).

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7.6 Recommendations

Some of the traits considered in the report could be recorded immediately. These include: i) lambsurvival, ii) ewe longevity, iii) ewe fat levels, iv) ‘gestation’ length, v) lambing ease and vi) ram scrotalcircumference. The incorporation of these into indexes would require varying degrees of programmingeffort including full genetic analyses of traits iv), v) and vi) and the identification of associations withother traits that are part of the breeding objective. Faecal Egg Count could also be recorded now but asthe application of the use of this indicator trait for nematode resistance in the UK is yet to be established(e.g. when to sample, how many sampling times, recommended levels of pasture contamination beforesampling etc.), in order to make the best use of this technology it may be preferable to wait until thisknowledge becomes available.

For flocks that have problems with mastitis, the use of Somatic Cell Count (SCC) could be instrumentalin improving resistance to this disease. Further research is needed to quantify the genetic variation inthis trait and to develop a protocol for its inclusion into breeding programmes.

More work is required (which is currently underway) before molecular tests for resistance to disease(footrot, nematodes, mastitis) can be used in practice.

A promising trait for easy care systems is ram libido, as defined by ram serving capacity. Theverification of existing tests from other research groups should be done using UK sheep breeds toestablish a useful protocol that could be used in the field. Further research work is needed before thecommencement of recording.

Further research is also needed for most of the behavioural traits, including the use of either physical orphysiological proxy traits.

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8 References

Abbot, K.A., Lewis, C.J., 2005. Current approaches to the management of ovine footrot. VeterinaryJournal 169: 28-41.

Abegaz, S., van Wyk, J. B. 2002. Genetic parameter estimates of survival, productivity and derivedbiological efficiency traits in Horro sheep of Ethiopia. Proceedings of the 7th World Congress onGenetics Applied to Livestock Production, Montpellier, France. Communication N° 12 02-36.

Aitchison, G.U., Spence, J.A., 1984. Dental disease in hill sheep: an abattoir study. Journal ofComparative Pathology 94(2): 285-300

Alexander, G., 1958. Behaviour of newly born lambs. Proceedings of the Australian Society of AnimalProduction 2: 123–125.

Alexander, G., 1962. Temperature regulation in the newborn lamb. IV. The effect of wind andevaporation of water from the coat on metabolic rate and body temperature. Australian Journal ofAgricultural Research 13: 82–99.

Alexander, G., 1988. What makes a good mother? Proceedings of the Australian Society for AnimalProduction 17:25-41

Alexander, G., Lynch, J.J., 1976. Phalaris windbreaks for shorn and fleeced lambing ewes. Proceedingsof the Australian Society of Animal Production 11: 161–164.

Alexander, G., Lynch, J.J., Mottershead, B.E., 1979. Use of shelter and selection of lambing sites byshorn and unshorn ewes in paddocks with closely or widely spaced shelters. Applied Animal Ethology5: 51–69.

Alexander, G., Lynch, J.J., Mottershead, B.E., Donnelly, J.B., 1980. Reduction in lamb mortality bymeans of grass wind-breaks: results of a five-year study. Proceedings of the Australian Society ofAnimal Production 13, 329–332.

Alexander, G., Poindron, P., Le Neindre, P., Stevens, D., Le´vy, F., Bradley, L., 1986. The importanceof the first hour post partum for exclusive maternal bonding in sheep. Applied Animal BehaviourScience 16: 295–300.

Alexander, G., Stevens, D., Bradley, L., 1990a. Distribution of field birth-sites of lambing ewes.Australian Journal of Experimental Agriculture 30, 759–767.

Alexander, G., Stevens, D., Bradley, L.R., Barwick, S.A., 1990b. Maternal behaviour in BorderLeicester, Glen Vale (Border Leicester derived) and Merino sheep. Australian journal of experimentalagriculture 30: 27-38

Alexander, G., Stevens, D., Kilgour, R., de Langen, H., Mottershead, B.E., Lynch, J.J., 1983.Separation of ewes from twin lambs: incidence in several sheep breeds. Applied Animal Ethology 10:301–317.

Alexander, G., Williams, D., 1966. Teat-seeking activity in new-born lambs: the effects of cold. Journalof Agricultural Science 67: 181–189.

Al-Shorepy, S.A., Notter, D.R., 1996. Genetic variation and covariation for ewe reproduction, lambgrowth and lamb scrotal circumference in a fall-lambing sheep flock. Journal of Animal Science 74:1490-1498

46

Alwan, M., 1983. Studies of the flock mating performance of Booroola Merino crossbred ram lambsand the foot conditions in the Booroola Merino crossbreds and Perendale sheep grazed on hill country.M. Agric. Sci. Thesis, Massey University.

Amer, P.R., Woolaston, R.R., Eady, S.J., McEwan, J.C., 1999. Economic values for sheep internalparasite resistance traits in New Zealand and Australia. Proceedings of the Association for theAdvancement of Animal Breeding and Genetics 13: 504-507

Ap Dewi, I., Saatci, M. and Ulutas, Z., 2002. Genetic parameters of weights, ultrasonic muscle and fatdepths, maternal effects and reproductive traits in Welsh Mountain Sheep. Animal Science 74: 399-408

Armbrust, T.A., Eisen, E.J., 1994. Reproductive performance in mice selected for divergence in bodyfat content. Journal of Animal Breeding and Genetics 111: 27-34

Arnold, G.W., 1981. Grazing behaviour. In: F.H.W. Morley (Editor), World Animal Science, Bl,Grazing Animals.

Arnold, G.W., Dudzinski, M.L., 1978. Ethology of free-ranging domestic animals. Developments inAnimal and Veterinary Sciences. Elsevier, Amsterdam.

Ashwell, M.S., Heyen, D.W., Sonstegard, T.S., Van Tassell, C.P., Da, Y., Van Raden, P.M., Ron, M.,Weller ,J.I., Lewin, H.A., 2004. Detection of Quantitative Trait Loci Affecting Milk Production, Health,and Reproductive Traits in Holstein Cattle. Journal of Dairy Science 87, 468-475.

Atkins, K.D., McGuirk, B.J., 1979. Selection of Merino sheep for resistance to fleece rot and bodystrike. Wool Technology and Sheep Breeding 27: 15-19

Baker, R.L., Clark, J.N., Harvey, T.G., Meyer, H.H., 1986. Inheritance of foot and jaw abnormalities insheep. Proceedings of the New Zealand Society of Animal Production 46: 93-100

Baker, R.L., Watson, T.G., Bisset, S.A., Vlassoff, A., Douch, P.G.C., 1991. Breeding sheep in NewZealand for resistance to internal parasites: research results and commercial application. In: Breedingfor Disease Resistant Sheep (Eds: Gray, G.D. and Woolaston, R.R.), Australian Wool Corp.,Melbourne, pp 19-32

Bakken, M., Vangen, O., Rauw, W.M., 1998. Biological limits to selection and animal welfare.Proceedings of the 6th World Congress on Genetics applied to Livestock Production, Armidale,Australia 27, 381

Baldwin, B.A., Shillito, E.E., 1974. The effect of ablation of the olfactory bulbs on parturition andmaternal behaviour of Soay sheep. Anim. Behav. 22, 220–223.

Barger, I.A., 1993. Influence of sex and reproductive status on susceptibility of ruminants to nematodeparasitism. International Journal for Parasitology 23: 463-469

Barillet, F., Rupp, R., Mignon-Grasteau, S., Astruc, J.M., Jacquin, M., 2001. Genetic analysis formastitis resistance and milk somatic cell score in French Lacaune dairy sheep. Genet. Sel Evol. 33, 397-415.

Baro, J.A., Carriedo, J.A., San Primitivo, F., 1994. Genetic parameters of test day measures for somaticcell count, milk yield and protein percentage of milking ewes. Journal of Dairy Science 77(9) 2658-2662

Bartley, D.J., Jackson, E., Johnston, K., Coop, R.L., Mitchell, G.B.B., Sales, J., Jackson, F. 2003. Asurvey of anthelmintic resistant nematode parasites in Scottish Blackface sheep flocks. VeterinaryParasitology. 117 (1-2) 61-71.

47

Beh, K.J., Hulme, D.J., Callaghan, M.J., Leish, Z., Lenane, I., Windon, R.G., Maddox, J.F., 2002. Agenome scan for quantitative trait loci affecting resistance to Trichostrongylus colubriformis in sheep.Anim. Genet. (33) 97-106.

Beilharz, R.G., Luxford, B.G., Wilkinson, J.L., 1993. Quantitative genetics and evolution - is ourunderstanding of genetics sufficient to explain evolution. Journal of Animal Breeding and Genetics-Zeitschrift für Tierzüchtung und Züchtungsbiologie 110, 161-170.

Bellows, R.A., Lammoglia, M.A., 2000. Effects of severity of dystocia on cold tolerance and serumconcentrations of glucose and cortisol in neonatal beef calves. Theriogenology 53, 803–813.

Bench, C. J., Price, E.O., Dally, M.R., Borgwardt, R.E., 2001. Artificial selection of rams for sexualperformance and its effect on the sexual behaviour and fecundity of male and female progeny.Applied Animal Behaviour Science 72:41–50.

Bilbe, E., Conington, J., McLean, K, Lambe, N, Bünger, L., 2005. Using Computerised Tomography toassess pelvic dimensions linked to dystocia and maternal behaviour score in Scottish-Blackface ewes.Proceedings of the British Society of Animal Science meeting, York, p.122 (Abstract).

Bindon, B.M., Piper, L.R., 1976. Assessment of new and traditional techniques of selection forreproduction rate. In: Sheep Breeding (Eds: Tomes, G.J., Robertson, D.E. and Lightfoot, R.J), WA Inst.Tech., Perth, Australia, pp 387-401

Bishop, S.C., Bairden, K., McKellar, Q.A., Stear, M.J., 1996. Genetic parameters for faecal egg countfollowing mixed, natural predominantly Ostertagia circumcincta infection and relationships with liveweight in young lambs. Animal Science, 63: 423-428.

Bishop, S.C., Jackson, F., Coop, R.L., Stear, M.J., 2004. Genetic parameters for resistance to nematodeinfections in Texel lambs. Animal Science, 78: 185-194.

Bishop, S.C., Stear, M.J., 1997. Modelling responses to selection for resistance to gastrointestinalparasites in sheep. Animal Science, 64: 469-478.

Bishop, S.C., Stear, M.J., 1999. Genetic and epidemiological relationships between productivity anddisease resistance: gastrointestinal parasite infection in growing lambs. Animal Science, 69: 515-525.

Bishop, S.C., Stear, M.J., 2001. Inheritance of, and factors affecting, egg counts during early lactationin Scottish Blackface ewes facing mixed, natural nematode infections. Anim. Sci. (73) 389-395.

Bishop, S.C., Stear, M.J., 2000. The use of a gamma-type function to assess the relationships of thebetween the number of adult Teladorsagia circumcincta and total egg output. Parasitology, 121: 435-440.

Bishop, S.C., Stear, M.J., 2003. Modelling of host genetics and resistance to infectious diseases:understanding and controlling nematode infections. Veterinary Parasitology 115: 147-166.

Bisset S.A., Morris C.A. 1996. Feasibility and implications of breeding sheep for resilience to nematodechallenge. International Journal for Parasitology 26(8-9): 857-868.

Bisset, S.A., Morris, C.A., McEwan, J.C., Vlassoff, A., 2001. Breeding sheep in New Zealand that areless reliant on anthelmintics to maintain health and productivity. New Zealand Veterinary Journal49(6): 236-246

Bisset, S.A., Morris, C.A., Squire, D.R., Hickey, S.M., 1996. Genetic of resilience to nematodeparasites in young Romney sheep – use of weight gain under challenge to assess individual anthelmintictreatment requirements. New Zealand Journal of Agricultural Research, 39 (3): 313-323

48

Bisset, S.A., Morris, C.A., Squire, D.R., Hickey, S.M., Wheeler, M., 1994. Genetics of resilience tonematode parasites in Romney sheep. New Zealand Journal of Agricultural Research 37: 521-534

Bisset, S.A., Vlassof, A., Morris, C.A., Southey, B.R., Baker, R.L., Parker, A.G.H., 1992. Heritabilityof and genetic correlations among faecal egg counts and productivity traits in Romney sheep. NewZealand Journal of Agricultural Research 35: 51-58

Bizelis, J.A., Charismiadou, M.A., Rogdakis, E., 2000. Metabolic changes during the perinatal periodin dairy sheep in relation to level of nutrition and breed. II. Early lactation. J. Anim. Physiol. Anim.Nutr. 84: 73-84

Blockey, M.A. de B., 1976. Serving capacity: a measure of the serving efficiency of bulls duringpasture mating. Theriogenology 6: 393-394.

Boichard, D., Grohs, C., Bourgeois, F., Cerqueira, F., Faugeras, R., Neau, A., Rupp, R., Amigues, Y.,Boscher, M.Y., Leveziel, H., 2003. Detection of genes influencing economic traits in three French dairycattle breeds. Genet. Sel Evol. 35: 77-101.

Bouix, J., Krupinski, J., Rzepecki, R., Nowosad, B., Skrzyzala, I., Roborzynski, M., Fudalewicz-Niemczyk, W., Skalska, M., Malczewski, A., Gruner, L., 1998. Genetic resistance to gastrointestinalnematode parasites in Polish long-wool sheep. International Journal for Parasitology 28: 1797-1804

Boyazoglu, J.G. and Treacher, T.T., 1978. Milk production in the ewe. In: Boyazoglu, J.G. andTreacher, T.T. (ed.) Proceedings of the Sheep and Goat Commission of the European Association forAnimal Production. European Association for Animal Production Publication No 23, Brussels.

Braden, A.W.H., Moule, G.R., 1964. Effects of stress on ovarian morphology and oestrous cycles inewes. Australian Journal of Agricultural Research 15: 937-949

Bradford, G.E., 1985. Selection for litter size. In: Genetics of Reproduction in Sheep (Eds: Land, R.B.and Robinson, D.W.), Butterworths, London, pp 3-18

Bradford, G.E., 2002. Selection for reproductive efficiency. Sheep and Goat Research Journal 17(3):6-10

Bradford, G.E., Hart, R., Quirke, J.F., Land, R.B., 1972. Genetic control of the duration of gestation insheep. Journal of Reproduction and Fertility 30: 459-463

Bradford, G.E., Quirke, J.F., Sitorious, P., Inounu, I., Tiesnamurti, B., Bell, F.L., Fletcher, I.C., Torell,D.T., 1986. Reproduction in Javanese sheep: evidence for a gene with large effect on ovulation rate andlitter size. Journal of Animal Science 63: 418-431

Brash, L.D., Fogarty, N.M., Barwick, S.A., Gilmour, A.R., 1994a. Genetic parameters for Australianmaternal and dual-purpose meatsheep breeds. I. Liveweight, wool production and reproduction inBorder Leicester and related types. Australian Journal of Agricultural Research 45: 459-468

Brash, L.D., Fogarty, N.M., Gilmour, A.R., 1994b. Genetic parameters for Australian maternal anddual-purpose meat sheep breeds. II. Liveweight, wool and reproduction in Corridale sheep. AustralianJournal of Agricultural Research 45: 469-480

Brash, L.D., Fogarty, N.M., Gilmour, A.R., 1994c. Reproductive performance and genetic parametersfor Australian Dorset sheep. Australian Journal of Agricultural Research 45: 427-441

Brinks, J.S., McInerney, M.J., Chenoweth, P.J., 1978. Relationship of age at puberty in heifers toreproductive traits in young bulls. Proceedings of the Western Section American Society of AnimalScience 29: 28-30

49

Brotherstone, S., Veerkamp, R.F., Hill, W.G., 1997. Genetic parameters for a simple predictor of thelifespan of Holstein-Friesian dairy cattle and its relationship to production. Animal Science 65: 31-37

Burfening, P. J. 1993. Direct and maternal genetic effects on lamb survival. Small RuminantResearch 11: 267–274.

Burfening, P.J., Davis, K.C., 1998. Genetic parameter estimates for scrotal circumference in ram lambsand estimated covariances with ewe body weight, fleece traits and reproductive rate. Sheep and GoatResearch 14: 121-126

Burris, M.J., Baugus, C.A., 1955. Milk composition and growth of suckling lambs. Journal of AnimalScience 14: 186-199

Burrow, H.M., 1997. Measurements of temperament and their relationships with performance traits ofbeef cattle. Animal Breeding Abstracts 65: 477-495

Burrow, H.M., 1998. The effects of inbreeding on productive and adaptive traits and temperament oftropical beef cattle. Livestock Production Science 55: 227-243

Cameron, A.W.N., Fairnie, I.J., Curnow, D.H., Keogh, E.J., Lindsay, D.R., 1984. The relationshipbetween testicular size and daily sperm output of rams. Proceedings of the Australian Society ofAnimal Production 15: 658

Carlén, E., Schneider, M. del P., Strandberg, E. 2005. Comparison between linear models and survivalanalysis for genetic evaluation of clinical mastitis in dairy cattle. Journal of Dairy Science 88: 797–803.

Christley, R. M., Morgan, K. L., Parkin, T. D. H., French, N. P. 2003. Factors related to the risk ofneonatal mortality, birth-weight and serum immunoglobulin concentration in lambs in the UK.Preventive Veterinary Medicine 57: 209-226.

Clarke, J.N., 1972. Current levels of performance in the Ruakura fertility flock of Romney sheep.Proceedings of the New Zealand Society of Animal Production 32: 99-111

Claxton, P.D., 1989. Antigentic classification of Bacterioides nodosus. In: Egerton, J.R. Yong, W.K.,Riffkin, G.G. (Eds) Footrot and foot abcesses of ruminants. CRC Press, 155-166.

Cloete, S.W.P., 1993. Observations on neonatal progress of Dormer and South African Mutton Merinolambs. South African Journal of Animal Science 23: 38–42.

Cloete, S. W. P., Greeff, J. C., Lewer, R. P., 2001. Environmental and genetic aspects of survival andearly liveweight in Western Australian Merino sheep. South African Journal of Animal Science 31:123-130.

Cloete, S.W.P., Olivier, J.J., Scholtz, A.J., 1998. Aspects of lambing and neonatal behaviour of duel-purpose sheep. Proceedings of the 6th World Congress on Genetics in Applied Livestock Production.Armidale, NSW, Australia 27: 39-42

Cloete, S.W.P., Scholtz, A.J., 1998. Lamb survival in relation to lambing and neonatal behaviour inmedium wool Merino lines divergently selected for ewe multiple rearing ability. Australian journal ofexperimental agriculture 38: 801-811

Cloete, S.W.P., Scholtz, A.J., Gilmour, A.R., Olivier, J.J., 2002. Genetic and environmental effects onlambing and neonatal behaviour of Dormer and South African Mutton Merino lambs. LivestockProduction Science 78: 183-193

50

Cloete, S.W.P., Van Wyk, J.B., Scholtz, A.J., Gilmour, A.R., 2003. Genetic and environmentalparameters for lambing behaviour in Merino lines divergently selected for ewe multiple rearing ability.Proceedings of the New Zealand Society of Animal Production 63: 169-172

Cockett, N., Bishop, S.C., Davies, G., Hadfield, T., Eng, S., Miller, J., 2005. Use of QTL to DetermineParasite Resistance in Sheep. Ann. Meet. Amer. Soc. Anim. Sci., July 24-28. Cincinnati, Ohio, USA.

Cockram, M.S., Ranson, M., Imlah, P., Goddard, P.J., Burrells, C., Harkiss, G.D., 1994. Thebehavioural, endocrine and immune responses of sheep to isolation. Animal Production 58: 389-399

Coltman, D.W., Wilson, K., Pilkington, J.G., Stear, M.J., Pemberton, J.M., 2001. A microsatellitepolymorphism in the gamma interferon gene is associated with resistance to gastrointestinal nematodesin a naturally-parasitized population of Soay sheep. Parasitol. (122) 571-582.

Conington, J. (nee Clark), 1990. Premature wool loss in sheep. MSc Thesis, Aberdeen University.

Conington, J., Bishop, S.C., Grundy, B., Waterhouse, A., Simm, G., 2001. Multi-trait selection indexesfor sustainable hill sheep production. Animal Science 73: 413-423

Conington, J., Bishop, S.C., Lambe, N.R., Bünger, L., Simm, G., 2006. Testing new selection indicesfor sustainable hill sheep production - lamb growth and carcass traits. Animal Science. In press.

Conington, J., Cao, G.Q., Stott, A., Bünger, L., 2005. Towards a better understanding of using breedingto control mastitis in sheep and cattle. Report prepared for Genesis Faraday and the Texel SheepSociety, June 2005.

Conington, J., Simm, G., Lawrence, A., 2003. Breeding to improve cow welfare. Sac Technical NoteT550

Conington, J., Bishop, S.C., Simm, G., 2002. Selection for sustainable UK hill sheep production. Proc.7th World Congress on Genetics Applied to Livestock Production., Montpelier, France. Communicationno. 24-06. ISBN 2-7380-1052-0.

Conington, J., Bishop, S.C., Waterhouse, A., Simm, G., 1998. A comparison of growth and carcasstraits in Scottish Blackface lambs sired by genetically lean or fat rams. Animal Science 67: 299-309

Conington, J., Watts, S., McLean, K., Lambe, N., Bünger, L., 2004. Using Computed Tomography(CT) to quantify bone properties in Scottish Blackface ewes. Proceedings of the British Society ofAnimal Science, p 123 (A)

Courtney, C.H., Gessner, R., Sholz, S.R., Loggins, P.E., 1986. The peri-parturient rise in faecal eggcounts in the three strains of the Florida Native ewes and its value in predicting resistance of the lambsto Haemonchus contortus. International Journal for Parasitology 16: 185-189

Courtney, C.H., Parker, C.F., McClure, K.E., Herd, R.P., 1984. A comparison of the peri-parturient risein faecal egg counts of exotic and domestic ewes. International Journal for Parasitology 14: 377-381

Courtney, C.H., Parker, C.F., McClure, K.E., Herd, R.P., 1985. Resistance of exotic and domesticlambs to experimental infection with Haemonchus contortus. International Journal for Parasitology15:101-109.

Cresswell, E., 1960. Ranging behaviour studies with Romney Marsh and Cheviot sheep in NewZealand. Animal Behaviour 8: 32-38.

Cumlivski, B., 1988. Resistance of sheep kept together of the breeds Kent (Romney Marsh), Lincoln,Cotswold and Leicester. In: Proceedings of the 3rd world congress on sheep and beef cattle breeding,Paris, France, Vol 1: 643-645

51

Cundiff, L.V., Gregory, K.E., Koch, R.M., 1982. Selection for increased survival from birth toweaning. Proceedings of the 2nd World Congress on Genetics in Applied Animal Production, Madrid,Spain, pp 310-337

Davis, G.H., Montgomery, G.W., Allison, A.J., Kelly, R.W., Bray, A.R., 1982. Segregation of a majorgene influencing fecundity in progeny of Booroola sheep. New Zealand Journal of AgriculturalResearch 25: 525-529

Davis, G.H., Shakell, G.H., Kyle, S.E., 1991. A putative major gene for prolificacy in Romney sheep.In: Major Genes for Reproduction in Sheep, 2nd International Workshop (Eds: Elsen, J.M., Bodin, L.and Thimonier, J.), Les Colloques, No 57: 61-65

Davies, G., Stear, M.J., Benothman, M., Abuagob, O., Kerr, A., Mitchell, S., Bishop, S.C., 2006.Quantitative trait loci associated with parasitic infection in Scottish Blackface sheep. Heredity(Accepted)

Davies, G., Stear, M.J., Bishop, S.C., 2005. Genetic relationships between indicator traits and nematodeparasite infection levels in 6 month old lambs. Animal Science 80: 143-150.

Deag, J.M., 1996. Behavioural ecology and the welfare of extensively farmed animals. AppliedAnimal Behaviour Science 49: 9-22

Dewhirst, F.E., Paster, B.J., La Fontaine, S., Rood, J.I., 1990. International Journal of SystematicBacteriology 40: 426-433

Diez-Tascón, C., Keane, O.M., Wilson, T., Zadissa, A., Hyndman, D.L., Baird, D.B., McEwan, J.C.,Crawford, A.M., 2005. Microarray analysis of selection lines from outbred populations to identifygenes involved with nematode parasite resistance in sheep. Phys. Genom. (21) 59-69.

Doligalska, M., Moskwa, B., Stear, M.J., 1999. Relationships among peripheral eosinophilia,eosinophil peroxidase activity, interleukin-5 concentration and faecal nematode egg count duringnatural, mixed gastrointestinal nematode infection. Veterinary Immunology and Immunopathology 70:299-308.

Doney, J.M., Gunn, R.G., Smith, W.F., 1976. Effects of premating environmental stress, ACTH,cortisone acetate or metyrapone on oestrus and ovulation in sheep. Journal of Agricultural Science(Cambridge) 87: 127-132

Douch, P.G.C., Green, R.S., Morris, C.A., Bisset, S.A., Vlassof, A., Baker, R.L., Watson, T.G.,Hurford, A.P., Wheeler, M., 1995. Genetic and phenotypic relationships among anti-Trichostrongyluscolubriformis antibody level, faecal egg count and body weight traits in grazing Romney sheep.Livestock Production Science (41) 121-132.

Dudzinski, M.L., Arnold, G.W., 1979. Factors influencing the grazing behaviour of sheep in aMediterranean climate. Applied Animal Ethology 5: 125-144.

Duguma, G., Cloete, S.W.P., Schoeman, S.J., Jordaan, G.F., 2002. Genetic parameters of testicularmeasurements in Merino rams and the influence of scrotal circumference on total flock fertility. SouthAfrican Journal of Animal Science 32: 76-82

Duncan, A.J., Mayes, R.W., Young, S.A., Lamb, C.S., MacEachern, P., 2001. Choice of foragingpatches by hill sheep given different opportunities to seek shelter and food. Animal Science 73: 563–570.

Dunlop, A.A., Hayman, R.H., 1958. Differences among Merino strains in resistance to fleece rot.Australian Journal of Agricultural Research 9: 260-266

52

Dwyer, C.M., 2002. Interactions between behavioural development, plasma cortisol andthermoregulation in the neonatal lamb. Proceedings of the British Society of Animal Science. 222.

Dwyer, C.M., 2003. Behavioural development in the neonatal lamb: Effect of maternal and birth-relatedfactors. Theriogenology 59, 1027–1050.

Dwyer, C.M., Lawrence, A.B., 1998. Variability in the expression of maternal behaviour inprimiparous sheep: effects of genotype and litter size. Applied Animal Behaviour Science 58: 311-330

Dwyer, C.M., Lawrence, A.B., 1999a. Does the behaviour of the neonate influence the expression ofmaternal behaviour in sheep? Behaviour 136, 367–389.

Dwyer, C.M., Lawrence, A.B., 1999b. Ewe-ewe and ewe–lamb behaviour in a hill and a lowland breedof sheep: A study using embryo transfer. Appl. Anim. Behav. Sci. 61, 319–334.

Dwyer, C.M., Lawrence, A.B., 2000. Effects of maternal genotype and behaviour on the behaviouraldevelopment of their offspring in sheep. Behaviour 137, 1629–1654.

Dwyer, C.M., Lawrence, A.B., 2005. A review of the behavioural and physiological adaptations of hilland lowland breeds of sheep that favour lamb survival. Applied Animal Behaviour Science 92: 235-260

Dwyer, C.M., Lawrence, A.B., Bishop, S.C., 2001. Effects of selection for lean tissue content onmaternal and neonatal lamb behaviours in Scottish Blackface sheep. Animal Science 72: 555–571.

Dwyer, C.M., Lawrence, A.B., Brown, H.E., Simm, G., 1996. Effect of ewe and lamb genotype ongestation length, lambing ease and neonatal behaviour in lambs. Reprod. Fertil. Dev. 8, 1123–1129.

Dwyer, C.M., McLean, K.A., Deans, L.A., Chirnside, J., Calvert, S.K., Lawrence, A.B., 1998.Vocalisations between mother and young in the sheep: effects of breed and maternal experience.Applied Animal Behaviour Science 58: 105–119.

Eady, S.J., Woolaston, R.R., Lewer, R.P., Raadsma, H.W., Swan, A.A., Ponzoni, R.W., 1998.Resistance to gastrointestinal parasites in Merino sheep: correlation with production traits. AustralianJournal of Agricultural Research 49: 1201-1211.

Eales, F.A., Small, J., 1980. Determinants of heat production in newborn lambs. Int. J. Biometeorol. 24:157–166.

Egerton, J.R., Roberts, D.S., 1971. Vaccination against ovine footrot. J. Comparative Pathology 81:179-370.

Egerton, J.R., Roberts, D.S., Parsonson, I.M., 1969. The aetiology and pathogenesis of ovine footrot I.A histological study of the bacterial invasion. Journal of Comp. Pathology 79: 207-216

Eisen, E.J. and Johnson, B.H., 1981. Correlated responses in male reproductive traits in mice selectedfor litter size and body weight. Genetics 99: 513-524

El Saied, U.M., Carriedo, J.A., De La Fuente, L.F., 1999. Genetic parameters of lactation cell countsand milk and protein yields in dairy ewes. Journal of Dairy Science 82, 639-644.

Elving, L., Grommers, F.J., van Eldik, P., 1986. Parturition difficulties and perinatal mortality in Texeland Milksheep. In: Proceedings of the Factors Affecting the Survival of Newborn Lambs, a seminar inthe CEC Programme of Coordunation of Agricultural Research, Brussels, 22 and 23 January 1985, pp115-122

53

Emanuelson, U., Danell, B., Philipsson, J., 1988. Genetic parameters for clinical mastitis, somatic cellcounts, and milk production estimated by multiple-trait restricted maximum likelihood. Journal of DairyScience 71, 467-476.

Emery, D.L., Stewart, D.J., Clark, B.L., 1984. The comparative susceptibility of five breeds of sheep tofootrot. Australian Veterinary Journal 61: 85-88

Erhard, H. W., Price, E.O., Dally, M.R., 1998. Competitive ability of rams selected for high and lowlevels of sexual performance.Anim. Sci. 66:403–408.

Escayg, A.P., Hickford, J.G.H., Bullock, D.W., 1997. Association between alleles of the ovine majorhistocompatibility complex and resistance to footrot. Research in Veterinary Science 63 (3): 283-287.

Everett-Hinks, J.M., Blair, H.T., Stafford, K.J., Lopez-Villalobos, N., 2005. Effect of ewe maternalbehaviour score on lamb survival and litter survival. Livestock production science, 93: 51-61

Fadelli, M.E., Leroy, P.L., 2001. Estimation of additive and non-additive genetic parameters forreproduction, growth and survival traits in crosses between Moroccan D’man and Timahdite sheepbreeds. Journal of Animal Breeding and Genetics, 341-353

Fahmy, M.H., 1996. Prolific sheep. CAB International, Oxon, UK.

Fahmy, M.H., Robert, S., Castonguay, F., 1997. Ewe and lamb behaviour at parturition in prolific andnon-prolific sheep. Canadian Journal of Animal Science 77: 9-15

Falconer, D.S., 1981. Introduction to Quantitative Genetics, 2nd ed., Longman, London, U.K.

Fell, L.R., Colditz, I.G., Walker, K.H., Watson, D.L., 1999. Associations between temperament,performance and immune function in cattle entering a commercial feedlot. Australian Journal ofExperimental Agriculture 39: 795-802

Fogarty, N.M., 1995. Genetic parameters for liveweight, fat and muscle measurements, woolproduction and reproduction in sheep: a review. Animal Breeding Abstracts 63: 101-143

Fogarty, N.M., Hopkins, D.L., van de Ven, R., 2000. Lamb production from diverse genotypes. 1.Lamb growth and survival and ewe performance. Animal Science 70: 135-145

Fogarty, N. M. 1995. Genetic parameters for live weight, fat and muscle measurements, woolproduction and reproduction in sheep: A review. Animal Breeding Abstracts 63: 101–143.

Fogarty, N.M., Ingham, V.M., Gilmour, A.R., Cummins, L.J., Gaunt, G.M., Stafford, J., Edwards,J.E.H., Banks, R.G., 2005. Genetic evaluation of crossbred lamb production. 1. Breed and fixed effectsfor birth and weaning weight of first-cross lambs, gestation length, and reproduction of base ewes.Australian Journal of Agricultural Research 56(5): 443-453

Fordyce, G., Goddard, M.E., Tyler, R., Williams, G., Toleman, M.A., 1985. Temperament and bruisingof Bos indicus cross cattle. Australian Journal of Experimental Agriculture 25: 283-288

Fossceco, S.L., Notter, D.R., 1995. Heritabilities and genetic correlations of body weight, testis growthand ewe lamb reproductive traits in crossbred sheep. Animal Science 60:185-195

Fox, M.T., Gerrelli, D., Shivalkar, P., Jacobs, D.E., 1989. Effect of omeprazole treatment on feedintake and blood gastrin and pepsinogen levels in the calf. Research in Veterinary Science 46: 280-282

Francis, D., Diorio, J., Liu, D., Meaney, M.J., 1999. Nongenomic transmission across generations ofmaternal behaviour and stress responses in the rat. Science 286, 1155–1158.

54

Fraser, A.F., Broom, D.M., 1990. Farm Animal Behaviour and Welfare. Balliere Tindall, London.

French, N. P. Parkin, T. D. H. Morgan, K. L., 1996. A case control study of blowfly strike in lambs.Veterinary Record 139: 16, 384-388.

French, N. P. Wall, R. Morgan, K. L., 1995. The seasonal pattern of sheep blowfly strike in Englandand Wales. Medical & Veterinary Entomology 9: 1, 1-8.

Gama, L.T., Dickerson, G.E., Young, L.D., Leymaster, K.A., 1991. Effects of breed, heterosis, age ofdam, litter size and birth weight on lamb mortality. Journal of Animal Science 69: 2727-2743

Gamble, H.R., Zajac, A.M., 1992. Resistance of St. Croix lambs to Haemonchus contortus inexperimentally and naturally acquired infections. Veterinary Parasitology 41: 211-225

Gauly, M., Kraus, M., Vervelde, L., van Leeuwen, M.A.W., Erhardt, G., 2002. Estimating geneticdifferences in natural resistance in Rhön and Merinoland sheep following experimental Haemonchuscontortus infection. Veterinary Parasitology 106: 55-67.

Gauthier, D., Thimonier, J., 1982. Seasonal variations in Creole heifer cyclicity: effect of growth, ageand emotivity. Reprod. Nutr. Dev. 22: 681-688

Gelez, H., Lindsay, D.R., Blache, D., Martin, G.B., Fabre-Nys, C., 2003. Temperament and sexualexperience affect female sexual behaviour in sheep. Applied Animal Behaviour Science 84: 81-87

Gibb, M.J., Treacher, T.T., 1982. The effect of body condition and nutrition during late pregnancy onthe performance of grazing ewes during lactation. Animal Production 34: 123-129

Gilmour, A.R., Raadsma, H.W., 1986. Estimating genetic variation and covariation for flystrikeincidence in Australian Merino sheep on an underlying normal scale. 3rd World Congress on Geneticsapplied to Livestock Production, Lincoln, Nebraska, USA, July 16-22, 1986. XII. Biotechnology,selection experiments, parameter estimation, design of breeding systems, management of geneticresources. pp 460-463

Gonyou, H.W., Stookey, J.M., 1983. Use of lambing cubicles and the behaviour of ewes at parturition.Journal of Animal Science 56, 787–791.

Gonyou, H.W., Stookey, J.M., 1985. Behavior of parturient ewes in group-lambing pens with andwithout cubicles. Applied Animal Behaviour Science 14, 163–171.

Goursaud, A.P., Nowak, R., 1999. Colostrum mediates the development of mother preference bynewborn lambs. Physiol. Behav. 67: 49–56.

Greef, J.C., Karlsson, L.J.E., 1997. Genetic relationships between faecal egg count and scouring inMerino sheep. Proceedings of the Association for the Advancement of Animal Breeding and Genetics12: 333-337

Greef, J.C., Karlsson, L.J.E., 1998. The genetic relationship between faecal consistency, faecal wormegg counts and wool traits in Merino sheep. Proceedings of the 6th World Congress on GeneticsApplied to Livestock Production, NSW, Australia, pp 63-66

Greef, J.C., Karlsson, L.J.E., 1999. Will selection for decreased faecal worm egg count result in anincrease in scouring? Proceedings of the Association for the Advancement of Animal Breeding andGenetics 13: 508-511

Greer, G., 2005. The costs of footrot and the impact of the footrot gene-marker test in New Zealand.Research Report – Agribusiness & Economics Research Unit, Lincoln University. No. 274.

55

Grogono-Thomas, R., Johnston, A.M., 1997. A study of ovine lameness. MAFF open contract OC5945K. Final report.

Gruner, L., Cortet, J., Sauve, C., Limouzin, C., Brunel, J.C., 2002. Evolution of nematode communityin grazing sheep selected for resistance and susceptibility to Teladorsagia circumcincta andTrichostrongylus colubriformis: a 4-year experiment. Vet. Parasitol. 109, 277-291.

Hafez, E.S.E., 1975. The Behaviour of Domestic Animals. Bailliere Tmdall, London.

Haley, C.S., Lee, G.J., Ritchie, M., Land, R.B., 1990. Direct response in males and correlatedresponses for reproduction in females to selection for testicular size adjusted for body weight in youngmale lambs. Journal of Reproduction and Fertility 89: 383-396

Hall, D.G., Fogarty, N.M., Gilmour, A.R., 1995. Performance of crossbred progeny of Trangie fertilityMerino and Booroola Merino rams and Poll Dorset ewes. 1. Lamb birth weight, survival and growth.Australian Journal of Experimental Agriculture 35: 1069-1074

Halliday, G. Ramsay, S. Scanlan, S. Younie, D., 1991. A survey of organic livestock health andtreatment. Kintail Land Research Foundation, UK. 45 pp.

Hanrahan, J.P., 1980. Ovulation rate as the selection criterion for litter size in sheep. Proceedings ofthe Australian Society of Animal Production 13: 405-408

Hanrahan, J.P., 1982. Selection for increased ovulation rate, litter size and embryo survival.Proceedings of the 2nd World Congress on Genetics Applied to Livestock Production 5: 294-309

Hanrahan, J.P., 1991. Evidence for single gene effects on ovulation rate in the Cambridge and Belclarebreeds. In: Major Genes for Reproduction in Sheep, 2nd International Workshop, Les Colloques, (eds:Elsen, J.M., Bodin, L., Thimonier, J.), No. 57: 93-102

Hanrahan, J.P., 2002. Response to divergent selection for ovulation rate in Finn sheep. In: Proceedingsof the 7th World Congress on Genetics Applied to Livestock Production 30: 673-676

Hanrahan, J.P., 2003. Aspects of reproductive performance in small ruminants – opportunities andchallenges. In: Reproduction in Domestic Ruminants (eds: Campbell, B.K., Webb, R., Dobson, H.,Doberska. C.), Reproduction supplement 61: 15-26

Hanrahan, J.P., Owen, J.B., 1985. Variation and repeatability of ovulation rate in Cambridge ewes.Animal Production 40: 529

Haughey, K.G., 1980. The effect of birth injury to the foetal nervous system on the survival and feedingbehaviour of lambs. In: Wodzicka-Tomasczewska, M., Edey, T.N., Lynch, J.J. (Eds.), Reviews in RuralScience, vol. 4. University of New England, Armidale, pp. 109–111.

Haughey, K.G., 1991. Perinatal lamb mortality – its investigation, causes and control. Journal of theSouth African Veterinary Association 62: 78-91

Haughey, K.G., 1993. Perinatal lamb mortality—its investigation, causes and control. Irish VeterinaryJournal 46, 9–28.

Haughey, K.G., George, J.M., McGuirk, B.J., 1985. The repeatability of rearing performance of Merinoand Dorset Horn ewes and its relationship with mature pelvic size. Aust. J. Exp. Agric. 25, 541–549.

Head, W.A., Hatfield, P.G., Fitzgerald, J.A., Hallford, D.M., Petersen, M.K., Stellflug, J.N., 1995.Effects of lifetime selection for kilograms of lamb weaned per ewe on ewe milk production, ewe andlamb feed intake and body weight change. Sheep and Goat Research Journal 11:78-83

56

Heath, M.F., Connan, R.M., 1991. Interaction of Ostertagia and Nematodirus species in sheep and thepotential of serum fructosamine determination in monitoring gastrointestinal parasitism. Research inVeterinary Science 51: 322-326.

Heringstad, B., Chang, Y.M., Gianola, D., Klemetsdal, G., 2005. Genetic association betweensusceptibility to clinical mastitis and protein yield in Norwegian dairy cattle. Journal of Dairy Science88, 1509-1514.

Hernandez, H., Serafin, N., Vazquez, H., Delgadillo, J.A., Poindron, P., 2001. Maternal selectivitysuppression through peripheral anosmia affects neither overall nursing frequency and duration, norlactation performance in ewes. Behav. Process 53, 203–209.

Herrtage, M.E., Saunders, R.W., Terlecki, S., 1974. Physical examination of cull ewes at point ofslaughter. Veterinary record 95 (12): 257-260

Hewson, R., Wilson, C.J., 1979. Home range and movements of Scottish Blackface sheep in Lochaber,north-west Scotland. Journal of Applied Ecology 16, 743–751.

Hickford J., 2000. Development of a sustainable method of natural footrot control. Report to the NZMeat Research and Development Council. Lincoln University.

Hickford J.G.H, Zhou, H., Slow, S., Fang, Q., 2004. Diversity of the ovine DQA2 gene. Journal ofAnimal Sciences 82 (6): 1553-1563.

Hiendleder, S., Thomsen, H., Reinsch, N., Bennewitz, J., Leyhe-Horn, B., Looft, C., Xu, N.,Medjugorac, I., Russ, I., Kuhn, C., Brockmann, G.A., Blumel, J., Brenig, B., Reinhardt, F., Reents, R.,Averdunk, G., Schwerin, M., Forster, M., Kalm, E., Erhardt, G., 2003. Mapping of QTL for BodyConformation and Behavior in Cattle. J. Hered. 94, 496-506.

Hinch, G.N., Kelly, R.W., Owens, J.L., Crosbie, S.F., 1983. Patterns of lamb survival in high fecundityBooroola flocks. Proceedings of the New Zealand Society of Animal Production 43: 29-32

Holmberg, M., Andersson-Eklund, L., 2004a. Quantitative Trait Loci Affecting Health Traits inSwedish Dairy Cattle. Journal of Dairy Science 87, 2653-2659.

Holmberg, M., Andersson-Eklund, L., 2004b. Quantitative trait loci affecting health traits in Swedishdairy cattle. Journal of Dairy Science 87, 2653-2659.

Holst, P. J., Fogarty, N. M., Stanley, D. F., 2002. Birth weights, meningeal lesions, and survival ofdiverse genotypes of lambs from Merino and crossbred ewes. Australian Journal of AgriculturalResearch 53: 175-181.

Hosie, B., 2003. Ovine footrot: A Scottish perspective. Sheep Veterinary Society autumn meeting,Bath. September 2003.

Houston, D.C., Maddox, J.G., 1974. Causes of mortality among young Scottish Blackface lambs.Veterinary Record 95: 575.

Hulet, C.V., Wiggins, E.L., Ercanbrack, S.K., 1969. Estrus in range lambs and its relationship tolifetime reproductive performance. J. Anim. Sci. 28, 246±247.

Hunter, R.F., 1960. Aims and methods in grazing behavior studies on hill pastures. Proceedings of the8th International Grassland Congress, pp. 454-458.

Ibarra, D., Laborde, D., van Lier, E., 2000. Repeatability and relationship with field matingperformance of a serving capacity pen test in rams. Small Rumin. Res. 37, 165–169.

57

Jackson, F. and Coop, R.L., 2000. The development of anthelmintic resistance in sheep nematodes.Parasitology 120: S95-S107

Janssen, M., Weimann, C., Gauly, M., Erhardt, G., 2002. Associations between infections withHaemonchus contortus and genetic markers on ovine chromosome 20. Proc. 7th World Congr. Genet.Appl. Livest. Prod. Comm. No. 13-11.

Jones, R.B., Hocking, P.M., 1999. Genetic selection for poultry behaviour: big bad wolf or friend inneed? Animal Welfare: 8: 343-359

Jonmundsson, J.V., Adalsteinsson, S., 1985. Single genes for fecundity in Icelandic sheep. In:Genetics of Reproduction in Sheep (eds: Land, R.B., Robinson, D.W.), Butterworths, London, pp 159-168

Kambara, T., McFarlane, R.G., Abell, T.J., McAnulty, R.W., Sykes, A.R., 1993. The effect of age anddietary protein on immunity and resistance in lambs vaccinated with Trichostrongylus colubriformis.International Journal for Parasitology 23: 471-476

Karlsson, L.J.E., Greeff, J.C., 1996. Preliminary genetic parameters of faecal worm egg count andscouring traits in Merino sheep selected for low worm egg count in a Mediterranean environment.Proceedings of the Australian Society of Animal Production 21: 477

Kelm, S.C., Detilleux, J.C., Freeman, A.E., Kehrli, M.E., Jr., Dietz, A.B., Fox, L.K., Butler, J.E.,Kasckovics, I., Kelley, D.H., 1997. Genetic association between parameters of inmate immunity andmeasures of mastitis in periparturient Holstein cattle. Journal of Dairy Science 80, 1767-1775.

Kerslake, J.I., Everett-Hinks, J.M., Campbell, A.W., 2005. Lamb survival: a new examination of an oldproblem. Proceedings of the New Zealand Society of Animal Production 65: 13-18

Key, C., Maclver, R.M., 1980. The effects of maternal influences on sheep: breed differences ingrazing, resting and courtship behaviour. Applied Animal Ethology 6: 33-48.

Kilgour, R. J. 1985. Mating behavior of rams in pens. Aust. J. Exp. Agric. 25:298–302.

Kilgour, R., de Langen, H., 1980. Neonatal behaviour in ‘easy-care’ sheep. In: Wodzicka-Tomaszewska, M., Edey, T.N., Lynch, J.J. (Eds.), Reviews in Rural Science, Behaviour in Relation toReproduction, Management and Welfare of Farm Animals, vol. 4. University of New England Press,Armidale, pp. 117–118.

Kilgour, R.J., Haughey, K.G., 1993. Pelvic size of ewes selected for lamb-rearing ability is greater thanthat of unselected Merino ewes. Animal Reproduction Science, Vol 31 (3-4), pp 237-242

Kilgour, R., Pearson, A.J., de Langen, H., 1975. Sheep dispersal patterns on hill country: Techniquesfor study and analysis. Proceedings of the New Zealand Society of Animal Production 35: 191-197.

Kilgour, R.J., Szantar-Coddington, M.R., 1995. Arena behavior of ewes selected for superior motheringability differs from that of unselected ewes. Animal Reproduction Science 37: 133–141.

Kilgour, R.J., Whale, R.G., 1980. The relation between mating activity of rams in pens and subsequentflock mating performance. Aust. J. Exp. Agric. Anim. Husb. 20, 5–8.

King, R.G., Kress, D.D., Anderson, D.C., Doornbos, D.E., Burfening, P.J., 1983. Genetic parameters inHerefords for puberty in heifers and scrotal circumference in bulls. Proceedings of the Western SectionAmerican Society of Animal Science 34: 11-13

58

Klungland, H., Sabry, A., Heringstad, B., Olsen, H.G., Gomez-Raya, L., Vage, D.I., Olsaker, I.,Odegard, J., Klemetsdal, G., Schulman, N., Vilkki, J., Ruane, J., Aasland, M., Ronningen, K., Lien, S.,2001. Quantitative trait loci affecting clinical mastitis and somatic cell count in dairy cattle. Mamm.Genome 12, 837-842.

Knight, T.W., Lynch, P.R., Hall, D.R.H., Hockey, H.U.P., 1988. Identification of factors contributing tothe improved lamb survival in Marshall Romney sheep. New Zealand Journal of Agricultural Research31: 259–271.

Knight, T.W., Wilson, L.D., Lynch, P.R., Hockey, H-U.P., 1989. Slope and the choice of birth sites byewes. New Zealand Journal of Agricultural Research 32: 193-198

Koyuncu, M., Tuncel, E., Kara Uzun, S., 2001. Some environmental effects on birth weight andgestation length in Karacabey Merino and genetic parameters. Ziraat Fakültesi Dergisi, AtatürkŰniversitesi 32 (2): 163-167

Kuchel, R.C., Lindsay, D.R., 1999. Maternal behaviour and the survival of lambs in superfine woolsheep. Reproduction, fertility and development 11:391-394

Kuhn, C., Bennewitz, J., Reinsch, N., Xu, N., Thomsen, H., Looft, C., Brockmann, G.A., Schwerin, M.,Weimann, C., Hiendleder, S., Erhardt, G., Medjugorac, I., Forster, M., Brenig, B., Reinhardt, F.,Reents, R., Russ, I., Averdunk, G., Blumel, J., Kalm, E., 2003. Quantitative Trait Loci Mapping ofFunctional Traits in the German Holstein Cattle Population. Journal of Dairy Science 86, 360-368.

Lambe, N.R., Brotherstone, S., Young, M.J., Conington, J., Simm, G., 2005. Genetic relationshipsbetween seasonal tissue levels in Scottish Blackface ewes and lamb growth traits. Animal Science81(1): 11-21

Lambe, N.R., Conington, J., Bishop, S.C., Waterhouse, A., Simm, G. 2001. A genetic analysis ofmaternal behaviour score in Scottish Blackface sheep. Animal Science 72: 415–425.

Lambe, N.R., Saurat, A., Conington, J., Bishop, S.C. Simm, G., 2006. Selection for carcass andmaternal traits: effects on lambing difficulties in Scottish Blackface hill ewes. Proceedings of theBritish Society of Animal Science, York. P 37(A)

Lambe, N.R., Young, M.J., Brotherstone, S., Kvame, T., Conington, J, Kolstad, K., Simm, G., 2003.Body tissue changes in Scottish Blackface ewes during one annual production cycle. Animal Science76:211-219.

Land, R.B., 1973. The expression of female sex-limited characters in the male. Nature 241: 208

Land, R.B., 1982. Indicators of reproductive potential. In: Proceedings of the World Congress onSheep and Cattle Breeding (Eds: Barton, R.A. and Smith, W.C.) 1: 365-373

Lawrence, A.B., Wood-Gush, D.G.M., 1988. Home-range behaviour and social organization of ScottishBlackface sheep. Journal of Applied Ecology, 25: 25-40.

Lawstuen, D.A., Hansen, L.B., Steuernagel, G.R., Johnson, L.P., 1988. Management traits scoredlinearly by dairy producers. Journal of Dairy Science 71: 788-799

Leathwick, D.M., Atkinson, D.S., Miller, C.M., Brown, A.E., Sutherland, I.A., 2002. Benefits ofreduced larval challenge through breeding for low faecal egg count in sheep. Novel Approaches III. AWorkshop meeting on helminth control in livestock in the new millennium. Moredun ResearchInstitute, July 2-5, 2002.

Lécrivain, E., Janeau, G., 1987. Isolation and shelter-seeking behaviour of ewes lambing in large andshrubby paddocks. Biol. Behav. 12, 127–148.

59

Legarra, A., Ugarte, E., 2001. Genetic parameters of milk traits in Laxta dairy sheep. Animal Science,73: 407-412

Legarra, A., Ugarte, E., 2005. Genetic parameters of udder traits, somatic cell score and milk yield inLaxta sheep. Journal of Dairy Science, 88, 2238-2245

Leitner, G., Chaffer, M., Shamay, A., Shapiro, F., Merin, U., Ezra, E., Saran, A., Silanikove, N., 2004.Changes in milk composition as affected by subclinical mastitis in sheep. Journal of Dairy Science 87,46-52.

Le Neindre, P., Boivin, X., Boissy, A., 1996. Handling of extensively kept animals. Applied AnimalBehaviour Science 49: 73-81

Le Neindre, P., Murphy, P.M., Boissy, A., Purvis, I.W., Lindsay, D., Orgeur, P., Bouix, J., Bibe´, B.,1998. Genetics of maternal ability in cattle and sheep. In: Proceedings of the 6th World Congress onGenetic Livestock Production, vol. 27. pp. 23–30.

Lent, P.C., 1974. Mother-infant relationships in ungulates. In: Geist, V., Walther, F. (Eds.), TheBehaviour of Ungulates and its Relationship to Management. IUCN Publication No. 24, Morges,Switzerland, pp. 14–55.

Lévy, F., Gervais, R., Kinderman, U., Litterio, M., Poindron, P., Porter, R., 1991. Effects of earlypostpartum separation on maternal selectivity and responsiveness in parturient ewes. Appl. Anim.Behav. Sci. 31: 101–110.

Lévy, F., Lacatelli, A., Piketty, V., Tillet, Y., Poindron, P., 1995. Involvement of the main but not theaccessory olfactory system in maternal behaviour of primiparous and multiparous ewes. Physiol. Behav.57, 97–104.

Lewis, R.D., Meyer, H.H., Gradin, J.L., Smith, A.W., 1988. Effectiveness of vaccination in controllingovine footrot. Journal of Animal Science, 67: 1160-1166

Ligda, C., Mavrogenis, A., Papadopoulos, T., Georgoudis, A. 2002. Genetic parameters for test daymilk traits and somatic cell counts in Chios dairy sheep. Options Méditerranéennes. Série A,Séminaires Méditerranéens. No 55, pp 55-59

Lindsay, D.R., Nowak, R., Putu, I.G., McNeill, D., 1990. Behavioural interactions between the eweand her young at parturition: a vital step for the lamb. In: Reproductive Physiology of Merino Sheep –concepts and consequences, University of Western Australia, Perth, pp 191-205

Lino, B.F., 1972. The output of spermatozoa in rams. II Relationship to scrotal circumference, testisweight, and the number of spermatozoa in different parts of the urogenital tract. Australian Journal ofBiological Science 25: 359-366

Litchfield A.M., Raadsma H.W., Hulme D.J., Brown S.C., Nicholas F.W., Egerton J.R., 1993. Diseaseresistance in Merino sheep. II. RFLPs in Class 2 MHC and their association with footrot. Journal ofAnimal Breeding and Genetics. 110 (5): 321-334

Litherland. A.J., Sorenson, E., Niezen, J., Bishop, D., 1992. A pilot evaluation of shedding sheepbreeds compared with non-shedding breeds for susceptibility to nematodes and flystrike. Proceedingsof the New Zealand Society of Animal Production 52: 233-235

Lopez-Villalobos, N., Garrick, D.J., 1999. Genetic parameter estimates for lamb survival in Romneysheep. Proceedings of the New Zealand Society of Animal Production, 59: 121-124

60

Lynch, J.J., Alexander, G., 1976. The effect of gramineous windbreaks on behaviour and lambmortality among shorn and unshorn Merino sheep during lambing. Applied Animal Ethology 2: 305–325.

Lynch, J.J., Hinch, G.N., Adams, D.B., 1992. The Behaviour of Sheep. Biological Principles andImplications. CAB International, Wallingford, UK

Lynch, J.J., Mottershead, B.E., Alexander, G., 1980. Sheltering behaviour and lamb mortality amongstshorn Merino ewes lambing in paddocks with a restricted area of shelter or no shelter. Applied AnimalEthology 6: 163–174.

Mason, W.A., 1984. Animal learning: experience, life modes and cognitive style. Verh. Dtsch. Zool.Ges. 77: 45-56

Matos, C.A.P., Thomas, D.L., 1992. Physiology and genetics of testicular size in sheep: a review.Livestock Production Science 32: 1-30

Matos, C.A.P., Thomas, D.L., Nash, T.G., Waldron, D.F., Stookey, J.M., 1992. Genetic analyses ofscrotal circumference size and growth in Rambouillet lambs. Journal of Animal Science 70: 43-50

Matos, C. A. P., Thomas, D. L., Young, L. D. and Gianola, D., 2000. Genetic analyses of lamb survivalin Rambouillet and Finnsheep flocks by linear and threshold models. Animal Science 71: 227-234.

Mackinnon, M.J., Hetzel, D.J.S., Corbet, N.J., Bryan, R.P., Dixon, R., 1990. Correlated responses toselection for cow fertility in a tropical beef herd. Animal Production 50: 417-424

MacLeod, J., 1992. Blowfly species composition in sheep myiasis in Britain. Medical & VeterinaryEntomology 6: 2, 177-178.

Mark, T., Fikse, W.F., Emanuelson, U., Philipsson, J., 2002. International genetic evaluations ofHolstein sires for milk somatic cell and clinical mastitis. Journal of Dairy Science 85, 2384-2392.

Marshall, K., van der Werf, J.H.J., Maddox, J.F., Graser, H-U., Zhang, Y., Walkden-Brown, S.W.,Kahn, L., 2005. A genome scan for quantitative trait loci for resistance to the gastrointestinal parasiteHaemonchus contortus in sheep. Proc. Assoc. Advmt. Anim. Breed. Genet. (16) 115.

Martin, G.B., Milton, J.T.B., Davidson, R.H., Banchero Hunzicker, G.E., Lindsay, D.R., Blache, D.,2004. Natural methods for increasing reproductive efficiency in small ruminants. AnimalReproduction Science 82-83: 231-246

Matika, O., van Wyk, J.B., Erasmus, G.J., Baker, R.L., 2003. Genetic parameter estimates in Sabisheep. Livestock Production Science 79: 17-28

McCutcheon, S.N., Holmes, C.W., McDonald, M.F., 1981. The starvation-exposure syndrome andneonatal lamb mortality. A Rev. Proc. N. Z. Soc. Anim. Prod. 41, 209–217.

McCutcheon, S.N., Holmes, C.W., McDonald, M.F., Rae, A.L., 1983. Resistance to cold stress in thenewborn lamb. 1. Responses of Romney, Drysdale - Romney, and Merino lambs to components of thethermal environment. New Zealand Journal of Agricultural Research 26: 169–174.

McEwan, J.C., Bisset, S.A. and Morris, C.A., 1997. The selection of sheep for natural resistance tointernal parasites. In: Sustainable Control of Internal Parasites in Ruminants (Ed. Barrell, G.K.),Lincoln University, Canterbury, New Zealand pp 161-182

McEwan, J.C., Dodds, K.G., Greer, G.J., Bain, W.E., Duncan, S.J., Wheeler, R., Knowler, K.J., Reid,P.J., Green, R.S. and Douch, P.G.C., 1995. Genetic estimates for parasite resistance traits in sheep andtheir correlations with production traits. New Zealand Journal of Zoology 22: 177

61

McEwan, J.C., Mason, P., Baker R.L., Clarke, J.N., Hickey, S.M. and Turner, K., 1992. Effect ofselection for productive traits on internal parasite resistance in sheep. Proceedings of the New ZealandSociety of Animal Production 52: 53-56

McEwan, J., Morris, C.A., Fennessy, P.F., Greer, G.J., Bain, W.E., Hickey, S.M., 2001. Selection forhigh or low backfat depth in Coopworth sheep: breeding-ewe traits. Animal Science 73: 241-252

McKellar, Q.A., Duncan, J.L., Armour, J and McWilliam, P., 1986. Response to transplanted adultOstertagia ostertagi in calves. Research in Veterinary Science 40:367-371

McMillan, W.H., Knight, T.W., 1982. Shearing and time of joining effects on reproduction in twotooth ewes. Proceedings of the New Zealand Society of Animal Production 42: 45-46

McSporran, K.D., Fielden, E.D., 1979. Studies on dystocia in sheep II: Pelvic measurements of eweswith histories of dystocia and eutocia. N. Z. J. Agric. 27, 75–78.

Memon, M.A., 1983. Male infertility. Veterinary Clinics of North America 5: 619-635

Mickelsen, W.D., Paisley, L.G., Dahmen, J.J., 1981. The effect of scrotal circumference, spermmotility and morphology in the ram on conception rates and lambing percentage in the ewe.Theriogenology 16(1): 53-59

Moore, C., Sanford, L.M., 1985. Genetic influence of predictability of testis function of rams.Research reports, Department of Animal Science, McGill University, pp 71-78

Morris, C.A., Bisset, S.A., Vlassoff, A., West, C.I., Wheeler, M., 1998. Faecal nematode egg counts inlactating ewes from Romney flocks selectively bred for divergence in lamb faecal egg count. Anim. Sci.(67) 283-288.

Morris, C.A., Bisset, S.A., Vlassoff, A., West, C.I., Wheeler, M., 2004. Genetic parameters forNematodirus spp. egg counts in Romney lambs in New Zealand. Animal Science 79: 33-39

Morris, C.A., Hickey, S.M., Clarke, J.N., 2000b. Genetic and environmental factors affecting lambsurvival at birth and through to weaning. New Zealand journal of agricultural research 43: 515-524

Morris, C.A., Vlassoff, A., Bisset, S.A., Baker, R.L., Watson, T.G., West, C.J., Wheeler, M. 2000a.Continued selection of Romney sheep for resistance or susceptibility to nematode infection: estimatesof direct and correlated responses. Animal Science, 70: 17-27.

Morris, C.A., Vlassof, A., Bisset, S.A., Baker, R.L., West, C.J., Hurford, A.P. 1997. Responses ofRomney sheep to selection for resistance or susceptibility to nematode infection. Animal Science 64:319-329.

Morris, O. S., Titchener, R. N., 1997: Blowfly species composition in sheep myiasis in Scotland.Medical & Veterinary Entomology 11: 3, 253-256.

Mukasa-Mugerwa, E., Ezaz, Z., 1992. Relationship of testicular growth and size to age, body weightand onset of puberty in Menz ram lambs. Theriogenology 38: 979-988

Mukasa-Mugerwa, E., Lahlou-Kassi, A., Anindo, D., Rege, J.E., Tembely, S., Tibbo, M., Baker, R.L.,2000. Between and within breed variation in lamb survival and the risk factors associated with majorcauses of mortality in indigenous Horro and Menz sheep in Ethiopia. Small Ruminant Research 37: 1-12

Murphy, P.M., Lindsay, D.R., Le Neindre, P., 1998. Temperament of merino ewes influences maternalbehaviour and survival of lambs. In: Proceedings of the 32nd Congress of the International Society forApplied Ethology, Clermont-Ferrand, France, p. 131.

62

Murphy, P.M., Lindsay, D.R., Purvis, I.W., 1994. The importance of the birth site on the survival ofMerino lambs. Proceedings of the Australian Society of Animal Production 20: 251–254.

Nash, M.L., Hungerford, L.L., Nash, T.G., Zinn, G.M., 1997. Risk factors for respiratory diseasemortality in lambs. Small Ruminant Research 26: 53-60

Nguti, R., Janssen, P., Rowlands, G.J., Audho, J.O, Baker, R.L., 2003. Survival of Red Massai, Dorperand crossbred lambs in the sub-humid tropics. Animal Science 76: 3-17

Nieuwhof, G.J., Bishop, S.C., 2005. Costs of the major endemic diseases of sheep in Great Britain andthe potential benefits of reduction in disease impact. Animal Science 81: 23-29.

Notter, D.R., 1998. The U.S. National Sheep Improvement Program: across-flock genetic evaluationsand new trait development. Journal of Animal Science 76:2324-2330

Notter, D.R., Lucas, J.R., McClaugherty, F.S., 1981. Accuracy of estimation of testis weight from insitu testis measures in ram lambs. Theriogenology 15: 227

Nowak, R., 1991. Development of mother discrimination by single and multiple newborn lambs.Animal Behaviour 42: 357–366.

Nowak, R., 1996. Neonatal survival: contributions from behavioural studies in sheep. Applied AnimalBehaviour Science 49: 61-72

Nowak, R.F., Lindsay, D.R., 1992. Discrimination of merino ewes by their newborn lambs: importantfor survival? Applied Animal Behaviour Science 34: 61–74.

Nowak, R., Murphy, T.M., Lindsay, D.R., Alster, P., Andersson, R., Uvna¨s-Moberg, K., 1997.Development of a preferential relationship with the mother by the newborn lamb: importance of thesucking activity. Physiol. Behav. 62, 681–688.

Nowak, R., Poindron, P., Le Neindre, P., Putu, I.G., 1987. Ability of 12-hour old merino and crossbredlambs to recognise their mothers. Applied Animal Behaviour Science 17: 263–271.

Nowak, R., Porter, R.H., Lévy, F., Orgeur, P., Schaal, B., 2000. Role of mother-young interactions inthe survival of offspring in domestic mammals. Rev. Reprod. 5, 153–163.

Obst, J.M., Ellis, J.V., 1977. Weather, ewe behaviour and lamb mortality. Agric. Rec. 4, 44–49.

O’Connor, C.E., 1996. Ewe maternal behaviour score and lamb growth: ten years on. Proceedings ofthe New Zealand Society of Animal Production 56: 107–109.

O’Connor, C.E., Jay, N.P., Nicol, A.M., Beatson, P.R., 1985. Ewe maternal behaviour score and lambsurvival. Proceedings of the New Zealand Society of Animal Production 45, 159–162.

O’Connor, C.E., Lawrence, A.B., 1992. Relationship between lamb vigour and ewe behaviour atparturition. Anim. Prod. 54, 361–366.

O’Doherty, J.V., Crosby, T.F., 1996. The effect of diet in late pregnancy on progesterone concentrationand colostrum yield in ewes. Theriogenology 46: 233-241

Olivier, W. J., Snyman, M. A., van Wyk, J. B., Erasmus, G. J. 1998. Genetic parameter estimates forfitness traits in South African Merino sheep. Livestock Production Science 56: 71–77.

Osinowo, O.A., Abubakar, B.Y., Trimnell, A.R., 1994. Genetic and phenotypic relationships betweengestation length, litter size and litter birth weight in Yankasa sheep. Animal Reproduction Science34(2): 111-118.

63

Othmane, M.H., de la Fuente, L.F., Carriedo, J.A., San Primitivo, F., 2002. Heritability and geneticcorrelations of test day milk yield and composition, individual laboratory cheese yield, and somatic cellcount for dairy ewes. J. Dairy Sci. 2002. Oct. 2692-2698.

Owen, J.B., 1971. Increasing reproductive efficiency of sheep. 10th World Congress of AnimalProduction, Versailles, Theme II, p4

Owens, J.L., Bindon, B.M., Edey, T.N., Piper, L.R., 1985. Behaviour at parturition and lamb survival ofBooroola Merino sheep. Livestock Production Science 13: 359–372.

Park, Y.H., Joo, Y.S., Park, J.Y., Moon, J.S., Kim, S.H., Kwon, N.H., Ahn, J.S., Davis, W.C., Davies,C.J., 2004. Characterization of lymphocyte subpopulations and major histocompatibility complexhaplotypes of mastitis-resistant and susceptible cows. J. Vet. Sci. 2004. Mar. 29-39.

Parker, C.T., Cross, R.T., Hamilton, K.L., 1983. Selection for footrot resistance in Targhee sheep.Journal of Animal Science 62: 164.

Paterson, K.A., McEwan, J.C., Dodds, K.G., Morris, C.A., Crawford, A.M., 1999. Fine mapping a locusaffecting host resistance to internal parasites in sheep. Proc. Assoc. Advmnt. Anim. Breed. Genet. (13)91-94.

Patterson, R. G., Patterson, H.M., 1989. A practical approach to breeding for footrot resistant Merinos.Journal of the New Zealand Mountain Lands Institute pp64-75.

Peart, J.N., 1968. Some effects of liveweight and body condition on the milk production of Blackfaceewes. Journal of Agricultural Science 70: 331-338

Perkins, A., Fitzgerald, J.A., 1992. Luteinizing hormone, testosterone, and behavioral response of male-oriented rams to estrous ewes and rams. J. Anim. Sci. 70, 1787–1794.

Perkins, A., Fitzgerald, J.A., Price, E.O., 1992. Sexual performance of rams in serving capacity testspredicts success in pen breeding. J. Anim. Sci. 70:2722–2725.

Perry B.D., Randolph, T.F., 1999. Improving the assessment of the economic impact of parasiticdiseases and of their control in production animals. Veterinary Parasitology 84, 145-168.

Pickup, H.E., 2003. Maternal behaviour in the ewe: consistency in the expression of maternal behaviourduring lactation and the effect of variation in maternal care on the development of offspring. Ph.D.thesis, University of Edinburgh.

Pickup, H.E., Dwyer, C.M., 2002. Breed differences in the expression of maternal care at parturitionpersist throughout the lactation period in sheep. Proceedings of the British Society of Animal Science70.

Piper, L.R., Bindon, B.M., 1982. Genetic segregation for fecundity in Booroola Merino sheep. In:Proceedings of World Congress on Sheep and Beef Cattle Breeding (eds: Barton, R.A., Smith, W.C.),The Dunmore Press Ltd., Palmerston North, New Zealand 1: 395-400

Poindron, P., Le Neindre, P., Le´vy, F., Keverne, E.B., 1984a. The physiological mechanisms of theacceptance of the newborn among sheep. Biol. Behav. 9, 65–88.

Poindron, P., Le Neindre, P., Raksanyi, I., Trillat, G., Orgeur, P., 1980. Importance of thecharacteristics of the young in the manifestation and establishment of maternal behaviour in sheep.Reprod. Nutr. Dev. 20, 817–826.

64

Poindron, P., Lévy, F., 1990. Physiological, sensory and experiential determinants of maternalbehaviour in sheep. In Mammalian Parenting : Biochemical, Neurobiological and Behaviouraldeterminants pp 133-156 (eds : Krasnegor, N.A., and Bridges, R.S.), Oxford University Press, Oxford,UK

Poindron, P., Le´vy, F., Krehbiel, D., 1988. Genital, olfactory and endocrine interactions in thedevelopment of maternal behaviour in the parturient ewe. Psychoneuroendocrinology 13, 99–125.

Poindron, P., Raksanyi, I., Orgeur, P., Le Neindre, P., 1984b. Comparaison du comportement maternelen bergerie a` la parturition chez des brebis primipares ou multipares de race Romanov, Pre´alpes duSud et Ile-de-France. Ge´ne´t. Se´l. Evol. 16, 503–522.

Pollard, J.C., Shaw, K.J., Littlejohn, R.P., 1999. A note of the sheltering behaviour of ewes before andafter lambing. Applied Animal Behaviour Science 61: 313–318.

Pollot, G.E., Greeff, J.C., 2004. Genotype x environment interactions and genetic parameters for fecalegg count and production traits of Merino sheep. J. Anim. Sci. 82:2840-2851.

Pollott, G. E., Greeff, J.C., 2004a. Genetic relationships between faecal egg count and production traitsin commercial Merino sheep flocks. Anim. Sci. 79:21–32.

Pollot, G.E., Karlsson, L.J., Eady, S., Greeff, J.C. 2004. Genetic parameters for indicators of hostresistance to parasites from weaning to hogget age in Merino sheep. J. Anim.Sci 82(10) 2852-2864.

Póti, P., Bedö, S., Mézes, M., Tözsér., J., 1999. Estimating reproduction ability of Hungarian Merinorams. Institute of Animal Husbandry, Department of Nutrition, Gödöllö University of AgriculturalSciences, Gödöllö, Hungary.

Price, E.O., 1985. Sexual behavior of large domestic farm animals: an overview. J. Anim. Sci. 61(Suppl. 3): 62-74.

Price, E. O. 1987. Male sexual behavior. Vet. Clin. North Am. Food Anim. Pract. 3:405–422.

Price, E. O., Borgwardt, R., Dally, M.R., Hemsworth, P.H., 1996. Repeated matings with individualewes by rams differing in sexual performance. J. Anim. Sci. 74:542–544.

Przekop, F., Wolinska-Witort, E., Mateusiak, K., Sadowski, B., Domanski, E., 1984. The effect ofprolonged stress on the oestrous cycles and prolactin secretion in sheep. Animal Reproduction Science,7: 333-342

Purser, A.F., Young, G.B., 1983. Mothering ability in two hill flocks. British Veterinary Journal139(4): 296-306

Purvis, I.W., Kilgour, R.J., Edey, T.N., Piper, L.R., 1984. Variation in testis diameter and servingcapacity within and between 14 Merino lines. Proceedings of the Australian Society of AnimalProduction 15: 545-548

Raadsma, H.W., 1991. Fleece rot and body strike in Merino sheep. V. Heritability of liability to bodystrike in weaner sheep under flywave conditions. Australian Journal of Agricultural Research 42

Raadsma, H.W., Egerton J.R., Wood, D., Kristo, C., Nicholas, F.W., 1994. Disease resistance in Merinosheep.III. Genetic variation in resistance following challenge and subsequent vaccination with anhomologous rDNA pilus vaccine. Journal of Animal Breeding and Genetics 111 (5-6): 367-390

Raadsma, H.A., Gilmour, A.R., Paxton, W.J., 1989. Fleece rot and body strike in Merino sheep. II.Phenotypic and genetic variation in liability to fleece rot following experimental induction. AustralianJournal of Agricultural Research 40: 207-220

65

Rathie, K.A., Tierney, M.L., Mulder, J.C., 1994. Assessing Wiltshire Horn-Merino crosses 1. Woolshedding, blowfly strike and wool production traits. Australian Journal of Experimental Agriculture 34:717-728

Rathie, K.A., Tierney, M.L., Mulder, J.C., 1994. Assessing Wiltshire Horn-Merino crosses. 1. Woolshedding, blowfly strike and wool production traits. Australian Journal of Experimental Agriculture 34:717-728

Rattray, P.V., Garrett, W.N., East, N.E., Hinman, N., 1974. Growth, development and composition ofthe ovine conceptus and mammary gland during pregnancy. Journal of Animal Science 38: 613-626

Rauw, W.M., Kanis, E., Noordhuizen-Stassen, E.N., Grommers, F.J., 1998. Undesirable side effects ofselection for high production efficiency in farm animals: a review. Livestock Production Science 56,15-33.

Réale, D., Gallant, B.Y., Leblanc, M., Festa-Bianchet, M., 2000. Consistency of temperament inbighorn ewes and correlates with behaviour and life history. Animal Behaviour 60: 589-597.

Reverter, A., Johnston, D.J., Ferguson, D.M., Perry, D., Goddard, M.E., Burrow, H.M., Oddy, V.H.,Thompson, J.M., Bindon, B.M., 2003. Genetic and phenotypic characterisation of animal, carcass andmeat quality traits from temperate and tropically adapted beef breeds. 4. Correlations among animal,carcass and meat quality traits. Australian Journal of Agricultural Research 54: 149-158

Riggio, V., Bishop, S. C., Finocchiaro, R. 2005. Genetic analysis of early lamb survival in extensivelyreared lambs. Italian Journal of Animal Science 4 (Suppl. 2): 73-75.

Roberts, D.S., Egerton, J.R., 1969. The aetiology and pathogenesis of ovine footrot II. The pathogenticassociation of Fusiformis nodosus and F. necrophorus. Journal of Comp. Pathology 79: 217-226

Robinson, J.J., Sinclair, K.D., McEvoy, T.G., 1999. Nutritional effects on foetal growth. AnimalScience 68: 315-331

Rubin C., Turner, A.S., Bain, S., Mallinckrodt, C., McLeod, K., 2001. Anabolism: Low mechanicalsignals strengthen bones. Nature 412: 603-604

Rupp, R., Boichard, D., 2003. Genetics of resistance to mastitis in dairy cattle. Vet. Res. 34, 671-688.

Rupp, R., Boichard, D., Barbat, A., Atruc, J.M., Lagriffoul, G., Barillet, F., 2002. Selection for mastitisresistance in French dairy sheep. Proc. 7th World Congress on Genetics Applied to LivestockProduction. Montpellier, France Paper no. 09-28,

Rupp, R., Lagriffoul, G., Astruc, J.M., Barillet, F., 2003. Genetic parameters for milk somatic cellscores and relationships with production traits in French Lacaune dairy sheep. J. Dairy Sci. 2003. Apr1476-1481.

Ruttle, J.L., Southward, G.M., 1988. Influence of age and scrotal circumference on breeding soundnessexamination of range rams. Theriogenology 29 (4): 945-949

Ryder, M.L., 1969. The development and structure of, and seasonal change in, the coat of someWiltshire sheep. Animal Production 11: 467-477

Safari, A., Fogarty, N.M., 2003. Genetic parameters for sheep production traits: estimates from theliterature. Technical Bulletin 49, NSW Agriculture, Orange Agricultural Institute, Orange, Australia.

Safari, E., Fogarty, N.M., Gilmour, A.R., 2005. A review of genetic parameter estimates for woolgrowth, meat and reproduction traits in sheep. Livestock Production Science 92: 271-289

66

Sakul, H., Boylan, W.J., 1992. Evaluation of U.S. sheep breeds for milk production and milkcomposition. Small Ruminant Research 7: 195-201.

Sakul, H., Bradford, G.E., Dally, M.R., 1999. Selection for litter size or weaning weight in rangesheep: I. Selection practiced and direct response. Sheep and Goat Research 15: 122-133

Samson, D.E., Slee, J., 1981. Factors affecting resistance to induced cooling in newborn lambs of 10breeds. Animal Production 33: 59–65.

Sargison, N., 2004. Blowfly Strike, Farmers Weekly Interactive special report.

Sawalha, R.M., Conington, J., Brotherstone, S., Villanueva, B., 2006. Analyses of lamb survival ofScottish Blackface sheep. Animal Science (in press).

Sawalha, R.M., Snowder, G.D., Keown, J.F., Van Vleck, L.D., 2005. Genetic relationship betweenmilk score and litter weight for Targhee, Columbia, Rambouillet and Polypay sheep. Journal of AnimalScience 83: 786-793

Scales, G.H., Bray, A.R., Baird, D.B., O’Connell, D., Knight, T.L., 2000. Effect of sire breed ongrowth, carcase and wool characteristics of lambs born to Merino ewes in New Zealand. New ZealandJournal of Agricultural Research 43: 93-100

Schulman, N.F., Viitala, S.M., de Koning, D.J., Virta, J., Maki-Tanila, A., Vilkki, J.H., 2004.Quantitative trait Loci for health traits in Finnish Ayrshire cattle. Journal of Dairy Science 87, 443-449.

Schrooten, C., Bovenhuis, H., Coppieters, W., Van Arendonk, J.A., 2000. Whole genome scan to detectquantitative trait loci for conformation and functional traits in dairy cattle. Journal of Dairy Science 83,795-806.

Schwaiger, F. W., Gostomski, D., Stear, M. J., Duncan, J. L., McKellar, Q. A., Epplen, J. T., Buitkamp,J. 1995. An ovine major histocompatibility complex DRB1 allele is associated with low faecal eggcounts following natural predominantly Ostertagia circumcincta infection. International Journal forParasitology 25, 815-822.

Serrano,M., Perez-Guzman, M.D., Montoro, V., Jurado, J.J., 2005. Genetic analysis of somatic cellscore and other milk traits in several lactations of Manchega ewes. Mean lactation approach.http://ressources. ciheam. org/om/pdf/a55/03600064. pdf

Sharif, S., Mallard, B.A., Wilkie, B.N., Sargeant, J.M., Scott, H.M., Dekkers, J.C., Leslie, K.E., 1998.Associations of the bovine major histocompatibility complex DRB3 (BoLA-DRB3) alleles withoccurrence of disease and milk somatic cell score in Canadian dairy cattle. Anim Genet. 29, 185-193.

Shillito, E., Alexander, G., 1975. Mutual recognition amongst ewe and lambs of four breeds of sheep(Ovis aries). Applied Animal Ethology 1: 151–165.

Shillito-Walser, E., 1980. Maternal recognition and breed identity in lambs living in a mixed flock ofJacob, Clun Forest and Dalesbred sheep. Applied Animal Ethology 6: 221–231.

Shillito-Walser, E., Hague, P., Walters, E., 1981. Vocal recognition of recorded lambs voices by ewesof three breeds of sheep. Behaviour 78:260–272.

Shillito-Walser, E., Willasden, S., Hague, P., 1982. Maternal vocal recognition in lambs born to Jacoband Dalesbred ewes after embryo transplantation between breeds. Applied Animal Ethology 8: 479–486.

Silva, J.R., Noakes, D.E., 1984. Pelvic dimensions, bodyweight and parturition in rare breeds of sheep.Veterinary Record 115, 242–245.

67

Simpson, S.P., Slee, J., 1998. The inheritance of non-response to noradrenaline in Scottish Blackfacelambs. Genetic Research 51: 65-69

Skerman, T.M., 1985. In: Footrot in ruminants (Eds Stewart, D.J., Peterson, J.E., McKern, N.M. andEmery, D.L.). Proceedings of a workshop, Melbourne, pp 77-78

Skerman, T.M., Erasmuson, S.K., Morrison, L.M., 1982. Duration of resistance to experimental footrotinfection in Romney and Merino sheep vaccinated with Bacteriodes nodosus oil adjuvant vaccine. NewZealand Veterinary Journal 30: 27-31

Skerman, T.M., Johnson, D.L., Kane, D.W., Clarke, J.N., 1988. Clinical footscald and footrot in a NewZealand Romney flock; phenotypic and genetic parameters. Australian Journal of AgriculturalResearch 39: 907-916

Skerman, T.M., Moorhouse, S.R., 1987. Broomfield Corriedales: a strain of sheep selectively bred forresistance to footrot. New Zealand Veterinary Journal 35: 101-106.

Slee, J., Alexander, G., Bradley, L.R., Jackson, N., Stevens, D., 1991. Genetic aspects of cold resistanceand related characters in newborn Merino lambs. Australian Journal of Experimental Agriculture 31:175–182.

Slee, J., Carter, H.B., 1961. A comparative study of fleece growth in Tasmanian Fine Merino andWiltshire Horn ewes. Journal of Agricultural Science (Cambridge) 57: 11-19

Slee, J., Carter., H.B., 1962. Fibre shedding and fibre-follicle relationships in the fleeces of WiltshireHorn x Scottish Blackface sheep crosses. Journal of Agricultural Science (Cambridge) 58: 309-326

Slee, J., Simpson, S.P., 1991. Description of the effects of a single gene which inhibits the normalmetabolic response of newborn lambs to exogenous noradrenaline. Research in Veterinary Science 51:34-39

Slee, J., Springbett, A., 1986. Early postnatal behaviour in lambs of ten breeds. Applied AnimalBehaviour Science 15: 229–240.

Slee, J., Stott, A.W., 1986. Genetic selection for cold resistance in Scottish Blackface lambs. AnimalProduction 43: 397–404.

Slen, S.B., Clark, R.D., Hironaka, R., 1963. A comparison of milk production and its relation to lambgrowth in five breeds of sheep. Canadian Journal of Animal Science 43: 16-21

Smith, B.A., Brinks, J.S. and Richardson, G.V., 1989. Relationships of sire scrotal circumference tooffspring reproduction and growth. Journal of Animal Science 67: 2881-2885

Smith, G.M., 1977. Factors affecting birth weight, dystocia and preweaning survival in sheep. Journalof Animal Science 44 (5): 745-753

Smith, J.A., Wilson, K., Pilkington, J.G., Pemberton, J.M., 1999. Heritable variation in resistance togastrointestinal nematodes in an unmanaged mammal population. Proceedings of the Royal Society ofLondon, Series B – Biological Sciences 266: 1283-1290

Smith, W.D., Jackson, F., Jackson, E., Williams, J., 1985. Age immunity to Ostertagia circumcincta:comparison of the local immune responses of 4-5 and 10 month-old lambs. Journal of ComparativePathology 95: 235-245.

Snowder, G.D., 2002. Composite trait selection for improving lamb production. Sheep and GoatResearch Journal 17: 42-49

68

Snowder, G.D., Glimp, H.A., 1991. Influence of breed, number of suckling lambs, and stage oflactation on ewe milk production and lamb growth under range conditions. Journal of Animal Science69: 923-930.

Snowder, G.D., Knight, A.D., Van Vleck, L.D., Bromley, C.M., Kellom, T.R., 2001a. Usefulness ofsubjective ovine milk scores: I. Associations with range ewe characteristics and lamb production.Journal of Animal Science 79: 811-818.

Snowder, G.D., Stellflug, J.N., Van Vleck, L.D. 2002. Heritability and repeatability of sexualperformance scores of rams. Journal of Animal Science 80:1508-1511.

Snowder, G.D., Stellflug, J.N., Van Vleck, L.D. 2004. Genetic correlation of ram sexual performancewith ewe reproductive traits of four sheep breeds. Applied Animal Behaviour Science 88:253-261

Snowder, G.D., Van Vleck, L.D., Knight, A.D., Kellom, T.R., Bromley, C.M., 2001b. Usefulness ofsubjective ovine milk scores: II. Genetic parameter estimates. Journal of Animal Science 79: 869-876.

Southey, B. R., Rodriguez-Zas, S. L., Leymaster, K. A. 2001. Survival analysis of lamb mortality in aterminal sire composite population. Journal of Animal Science 79: 2298–2306.

Southey, B. R., Rodriguez-Zas, S. L., Leymaster, K. A., 2004. Competing risks analysis of lambmortality in a terminal sire composite population. Journal of Animal Science 82: 2892-2899

Stevens, D., Alexander, G., Lynch, J.J., 1981. Do merinos seek isolation or shelter at lambing? AppliedAnimal Ethology 7, 149–155.

Stevens, D., Alexander, G., Lynch, J.J., 1982. Lamb mortality due to inadequate care of twins bymerino ewes. Applied Animal Ethology 8: 243–252.

Stevens, D., Alexander, G., Mottershead, B., Lynch, J.J., 1984. Role of the lamb in post-partumseparation of ewes from twin lambs. Proceedings of the Australian Journal of Animal Production 15:751.

Stear, M. J., Bairden, K., McKellar, Q. A., Scott, I., Strain, S. A. J. 1999. The relationship between thenumber and size of nematodes in the abomasum and the concentration of pepsinogen in ovine plasma.Research in Veterinary Science 67, 89-92.

Stear, M.J., Bishop, S.C., Bairden, K., Duncan, J.L., Gettinby, G., Holmes, P.H., McKellar, Q.A., Park,M., Strain, S., Murray, M., 1997. The heritability of worm burden and worm fecundity in lambsfollowing natural nematode infection. Nature 389:27

Stear, M.J., Bishop, S.C., Doligalska, M., Duncan, J.L., Holmes, P.H., Irvine, J., McCririe, L.,McKellar, Q.A., Sinski, E., Murray, M., 1995. Regulation of egg production, worm burden, wormlength and worm fecundity by host responses in sheep infected with Ostertagia circumcincta. ParasiteImmunology 17: 643-652.

Stear, M.J., Bishop, S.C., Henderson, N.G., Scott, I.A., 2003. Key mechanism of pathogenesis in sheepinfected with the nematode Teladorsagia circumcincta. Animal Health Research Reviews 4: 45-52

Stear, M. J., Eckersall, P. D., Graham, P. A., McKellar, Q. A., Mitchell, S., Bishop, S. C. 2001.Fructosamine concentration and resistance to natural, predominantly Teladorsagia circumcinctainfection. Parasitology 123, 211-218.

Stear, M. J., Henderson, N. G., Kerr, A., McKellar, Q. A., Mitchell, S., Seeley, C., Bishop, S. C. 2002.Eosinophilia as a marker of resistance to Teladorsagia circumcincta in Scottish Blackface lambsParasitology 124, 553-560.

69

Stear, M.J., Innocent, G.T., Buitkamp, J. 2005. The evolution and maintenance of polymorphism in themajor histocompatibility complex Veterinary Immunology and Immunopathology, 108, 1-2, 53-57

Stellflug, J.N., Cockett, N.E., Lewis, G.S., 2006. Relationship between sexual behaviour classificationsof rams and lambs sired in a competitive breeding environment. Journal of Animal Science. 84:463-468.

Stevenson, L.M., Huntley, J.F., Smith, W.D., Jones, D.G., 1994. Local eosinophil- and mast cell-related responses in abomasal nematode infections of lambs. FEMS Immunology and MedicalMicrobiology 8: 167-174

Stewart, D.J., Emery, D.W., Clark, B.L., Peterson, J.E., Iyer, H., Jarrett, R.G., 1985. Differencesbetween breeds of sheep in their response to Bacteroides nodosus vaccines. Australian VeterinaryJournal 62: 116-120

Strain, S. A. J., Bishop, S. C., Henderson, N. G., Kerr, A., McKellar, Q. A., Mitchell, S. and Stear, M. J.2002. The genetic control of IgA activity against Teladorsagia circumcincta and its association withparasite resistance in naturally infected sheep Parasitology 124, 545-552.

Sykes, A.R., Griffiths, R.G., Slee, J., 1976. Influence of breed, birth weight and weather on the bodytemperature of newborn lambs. Animal Production 22: 395–402.

Szantar-Coddington, M.R., 1994. Genetic improvement of lamb survival in the Australian Merino:behavioural and physiological indicators of maternal ability. M.Rur.Sci. thesis, University of NewEngland, Armidale, Australia.

Terrazas, A., Nowak, R., Serafı´n, N., Ferreira, G., Le´vy, F., Poindron, P., 2002. Twenty-four-hour-oldlambs rely more on maternal behaviour than on the learning of individual characteristics to discriminatebetween their own and an alien mother. Dev. Psychobiol. 40 : 408–418.

Terrill, C. E. 1937. Measurement of reproductive capacity as an aid in selection of rams of high fertility.Pages 311–331 in Proc. 30th Annu. Meet. Amer. Soc. Anim. Prod., Chicago, IL.

Tierney, M.L., 1978. Easy care Merinos through cross-breeding with Wiltshire Horn sheep. WoolTechnology and Sheep Breeding 26 (3): 21-25

Toelle, V.D., Robison, O.W., 1985. Estimates of genetic correlations between testicular measurementsand female reproductive traits in cattle. Journal of Animal Science 60: 89-100

Torres-Hernandez, G., Hohenboken, W., 1980. Relationship between ewe milk production andcomposition and preweaning lamb weight gain. Journal of Animal Science 50: 597-603

Treacher, T.T., 1983. Nutrient requirements for lactation in the ewe. In: Haresign, W. (ed) SheepProduction pp 133-153. Butterworths, London.

Turner, H.N., Hayman, L.K., Triffit, L.K., Prunster, R.W., 1962. Response to selection for multiplebirths in the Australian Merino: a progress report. Animal Production 4: 165-176

Vanimisetti, H.B., Andrew, S.L., Zajac, A.M., Notter, D.R., 2004. Inheritance of fecal egg count andpacked cell volume and their relationship with production traits in sheep infected with Haemonchuscontortus. J. Anim. Sci., 82:1602-1611

Van Niekerk, C.H., Belonje, P.C., Hunter, G.L., 1968. Early embryo mortality and resorption inMerino ewes due to malnutrition. In: Proceedings of the Sixth International Congress on AnimalReproduction and AI, Paris, vol 1: 455-458

70

Vatankhah, M., Edris, M.A., Salehi, A., 2000. Study on gestation length and its relationship withnumbers, sex and birth weight of lambs in each delivery in Bakhtiari sheep. Pajouhesh-va-Sazandegi46: 122-125

Veerkamp, R.F., Hill, W.G., Stott, A.W., Brotherstone, S., Simm, G., 1995. Selection for longevity andyield in dairy cows using transmitting abilities for type and yield. Animal Science 61: 189-197

Veerkamp, R.F., Stott, A.W., Hill, W.G., Brotherstone, S., 1998. The economic value of somatic cellcount payment schemes for UK dairy cattle breeding programmes. Animal Science 66, 293-298.

Viérin, M., Bouissou, M-F., 2002. Influence of maternal experience on fear reactions in ewes. AppliedAnimal Behaviour Science 75, 307–315.

Vipond, J., 2006. Easicare sheep systems. SAC Select Services, Penicuik, Scotland

Voisinet, B.D., Grandin, T., Tatum, J.D., O'Connor, S.F., Struthers, J.J., 1997. Feedlot cattle with calmtemperaments have a higher average daily weight gain than cattle with excitable temperaments. Journalof Animal Science 75: 892-896

Waldron, D.F., Thomas, D.L., 1992. Increased litter size in Rambouillet sheep: II. Expected responsesfrom alternative selection criteria. Journal of Animal Science 70: 3345-3350

Walkley, J.R., Smith, C., 1980. The use of physiological traits in genetic selection for litter size insheep. Journal of Reproduction and Fertility 59: 83

Wang, C.T., Dickerson, G.E., 1991. Simulation of life-cycle efficiency of lamb and wool productionfor genetic levels of competent traits. Journal of Animal Science 69: 4324-4337

Wassink, G.J., Green, L.E., 2001. Farmers’ practices and attitudes towards footrot in sheep. VeterinaryRecord 149: 489-490.

Watson, T.G., Baker, R.L., Harvey, T.G., 1986. Genetic variation in resistance or tolerance to internalnematode parasites in strains of sheep at Rotomahana. Proceedings of the New Zealand Society ofAnimal Production. Vol 46: 23-26

Watson, T.G., Hosking, R., Morris, C.A., Hurford, A.P. 1995. Faecal nematode egg counts andhaemotology in Perendale ewes near lambing. Proceedings of the New Zealand Society of AnimalProduction 55: 202-204.

Webster, A.J.F., 1993. Environment: heat and cold tolerance. Proceedings of the Sheep VeterinarySociety 17: 123- 128.

Wiggins, E.L., Terrill, C.E., Emik, L.O., 1953. Relationships between libido, semen characteristics andfertility in range rams. J. Anim. Sci. 12, 684–694.

Wilkins, J.F., Kilgour, R.J., 1978. Early reproductive performance in female progeny of rams selectedon serving capacity (Abstr.). In: Proceedings of the 10th Annual Conference on Australian Society ofReproduction Biology, p. 22.

Wilson, D.E., Morrical, D.G., 1991. The National Sheep Improvement Program: a review. Journal ofAnimal Science 69: 3872-3881

Wilson, D.S., Clark, A.B., Coleman, K., Dearstyne, T., 1994. Shyness and boldness in humans andother animals. Trends. Ecol. Evol. 9: 442-446

Wolff, J.E., Baker, R.L., Dobbie, P.M., Ford, A.J., Jordon, R.B., 1987. Genetic aspects of coldresistance in newborn lambs. Proceedings of the New Zealand Society of Animal Production 47: 93-98

71

Woolaston, R.R. 1992. Selection of Merino sheep for increased and decreased resistance toHaemonchus contortus: peri-parturient effects on faecal egg counts. International Journal forParasitology 22: 947-953.

Woolaston, R.R., 1994. Preliminary evaluation of strategies to breed Merinos for resistance toroundworms. Proceedings of the 5th world congress on genetics applied to livestock production,Guelph, Vol 20: 281-284

Woolaston, R.R., Piper, L.R. 1996. Selection of merino sheep for resistance to Haemonchus contortus:genetic variation. Animal Science 62: 451-460.

Woolaston, R.R., Windon, R.G. 2001. Selection of sheep for response to Trichostrongyluscolubriformis larvae: genetic parameters. Animal Science, 73: 41-48.

Woolliams, C., Suttle, N.F., Woolhams, J.A., Jones, D.G., Wiener, G., 1986. Studies on lambs fromlines genetically selected for high and low copper status. 1. Differences in mortality. Animal Production43: 293-302.

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9 Appendices

9.1 Footrot scoring system

8-point footrot scoring system developed by Raadsma et al., 1993

Trait Range DerivationAffected - At least one foot affected, adjusted for healingUnderrun - At least one foot underrun, adjusted for healingNo. of feetaffected

0-4

No. of feetunderrun

0-4

Overall grade 0-5 Overall gradeHealing - At least one affected foot showing a reduction in the inflammation of the

lesions, with signs of dry footrot lesions.Healed, partial - At least one affected foot showing complete healing of footrot lesions,

with no signs of inflammation or exudation in the footrot lesion.Healed, total - All affected feet showing complete healing of footrot lesions, with no

signs of inflammation or exudation in any of the footrot lesions.

9.2 Molecular markers for mastitis resistance in cattle

Chromo Trait Closestmarker(positioncM)

P(%) Locationconfidenceinterval(cM).2/

Reference

3(putative)

CM Klungland et al., 2001

4(putative)

CM Klungland et al., 2001

6 CM Klungland et al., 2001

9 CM TGLA73 ***(chromosome)†(genome)

Holmberg &Andersson-Eklund,2004a

10 CM 0.02 1 Schulman et al., 2004

11 CM INRA177 *(chromosome)NS(genome)

Holmberg &Andersson-Eklund,2004a

11 CM <0.01 1 Schulman et al., 2004

14(putative)

CM Klungland et al., 2001

18 CM TGLA227 0.02(P-value atchromosome-wise significancelevel)

120 Schulman et al., 2004

25 CM ILSTS102-RM404

*(chromosome)NS(genome)

Holmberg &Andersson-Eklund,2004a

27(putative)

CM Klungland et al., 2001

73

Chromo Trait Closestmarker(positioncM)

P(%) Locationconfidenceinterval(cM).2/

Reference

14 CM(cofactor analysis)

BMS1747-BMS740

<0.01(P-value atchromosome-wise significancelevel)

25 Schulman et al., 2004

21 CM(cofactor analysis)

RM151-INRA103

0.01(P-value atchromosome-wise significancelevel)

23 Schulman et al., 2004

6 Quality ofudder

0.000/0.008 89 Hiendleder et al., 2003

3 SCC BMC5227 0.0317(chromosome-wise P-value)

171 Schrooten et al., 2000

7 SCC(putative)

BMS2258-OarAE129

0.025(chromosome-wise)

107 Kuhn et al., 2003

9 SCC CSSM56 **(chromosome)

NS(genome)

Holmberg &Andersson-Eklund,2004a

11 SCC BMS7169 ****(chromosome)

**(genome)

Holmberg &Andersson-Eklund,2004a

18 SCC BM7109-ILSTS002

0.0103(chromosome-wise P-value)

70 Schrooten et al., 2000

18 SCC TGLA227 0.058(genome-wise)

117 Kuhn et al., 2003

23 SCC BM1443 *(chromosome)NS(genome)

Holmberg &Andersson-Eklund,2004a

27 SCC(putative)

BM3507-TGLA179

0.004(chromosome-wise)

8 Kuhn et al., 2003

10 SCC(putative)

TGLA378-TGLA102

0.027(chromosome-wise)

49 Kuhn et al., 2003

1 SCS(cofactoranalysis)

<0.01(P-value atchromosome-wise significancelevel)

59 Schulman et al., 2004

3 SCS 0.01 (P-value atchromosome-wise significancelevel)

105 Schulman et al., 2004

5 SCS BL37-BM1819

9.1(F statistic)(chromosome-wise) (P<0.01)

54 Ashwell et al., 2004

7 SCS BM6117-BMS2258

8.8(F statistic)(chromosome-wise) (P<0.01)

61 Ashwell et al., 2004

7 SCS BM6117-BMS2258

3.2 (F statistic)(chromosome-wise)(P<0.01)

67 Ashwell et al., 2004

11 SCS 0.03 (P-value atchromosome-wise significance

63 Schulman et al., 2004

74

Chromo Trait Closestmarker(positioncM)

P(%) Locationconfidenceinterval(cM).2/

Reference

level)

14 SCS 0.01 (P-value atchromosome-wise significancelevel)

63 Schulman et al., 2004

15

SCS(genome-wisesignificant)

BMS2684 0.0535_45 /22_48 Boichard et al., 2003

15 SCS BMS2684-HBB

9.8(F statistic)(chromosome-wise) (P<0.01)

34 Ashwell et al., 2004

18 SCS 0.02 (P-value atchromosome-wise significancelevel)

113 Schulman et al., 2004

20 SCS RM310-TGLA126

11.8(F statistic)(chromosome-wise) (P<0.01)

29 Ashwell et al., 2004

21 SCS(cofactoranalysis)

<0.01(P-value atchromosome-wise significancelevel)

51 Schulman et al., 2004

22 SCS BMS875-BM4102

3.32 (F statistic)(chromosome-wise)(P<0.01)

80 Ashwell et al., 2004

23 SCS BB705-BM1818

12.7(F statistic)(chromosome-wise) (P<0.01)

50 Ashwell et al., 2004

23 SCS BB705-BM1818

3.02 (F statistic)(chromosome-wise)(P<0.01)

41 Ashwell et al., 2004

23 SCS(cofactoranalysis)

0.01(P-value atchromosome-wise significancelevel)

7 Schulman et al., 2004

24 SCS(cofactoranalysis)

<0.01(P-value atchromosome-wise significancelevel)

28 Schulman et al., 2004

26 SCS Centromere-BM1314

11.2(F statistic)(chromosome-wise)(P<0.01)

0 Ashwell et al., 2004

26 SCS Centromere-BM1314

11.0(F statistic)(chromosome-wise)(P<0.01)

0 Ashwell et al., 2004

75

Chromo Trait Closestmarker(positioncM)

P(%) Locationconfidenceinterval(cM).2/

Reference

26 SCS Centromere-BM1314

2.72 (F statistic)(chromosome-wise)(P<0.01)

0 Ashwell et al., 2004

27 SCS 0.02 (P-value atchromosome-wise significancelevel)

3 Schulman et al., 2004

29 SCS BMC1206-BMS1948

8.0 (F statistic)(chromosome-wise)(P<0.01)

50 Ashwell et al., 2004

29 SCS 0.01 (P-value atchromosome-wise significancelevel)

14 Schulman et al., 2004

9 SCS(chromosome-wisesignificant)

BMS1967 1.3 Boichard et al., 2003

21 SCS(chromosome-wisesignificant)

TGLA122 1.5 Boichard et al., 2003

23 SCS(chromosome-wisesignificant)

RM33 1.7 Boichard et al., 2003

10 SCS(genome-wisesignificant)

DIK20 0.9 66_90 /6_92

Boichard et al., 2003

5 Udder depth 0.046(chromosome-/experiment-wisethresholds)

106(location)

Hiendleder et al., 2003

6 Udder depth 0.000/0.008 89 Hiendleder et al., 2003

9.3 Maternal behaviour scores at tagging

Description of maternal behaviour score (MBS)a MBS Score interpretationb

Ewe flees at the approach of the shepherd, shows nointerest in the lambs and does not return.

1

Ewe retreats further than 10m but comes back to herlambs as the shepherd leaves them.

2 Poor mothers – cull annually

Ewe retreats to such a distance that tag identification isdifficult (5-10m)

3 Good mothers

Ewe retreats but stays within 5m 4Ewe stays close to the shepherd during the handling of herlambs.

5 Excellent mothers

a As described by O’Connor et al. (1985)b Everett-Hincks et al., 2005

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9.4 Trait checklist

Trait Av.Heritability

Definition Ram,ewe orlamb

Age ofmeasurement

Ease ofrecording

Expensiveto record

Key references

Breeding for resistance to diseaseNematodesFaecal egg count 0.2 – 0.4 Number of eggs per gram of faeces after a

period of known challenge of infectivelarvae

Lamb FEC 1: 6-8 weeksafter weaningFEC 2: 6-8 weeksafter FEC1

Timeconsuming

Yes Morris et al., 1997 and2000a; Woolaston andPiper, 1996;Woolaston andWindon, 2001

ImmunoglobulinA (IgA) levels

0.57 Activity of IgA against a somatic extractof 4th stage larvae from T. circumcincta

Lamb 7-9 months Involvesbloodsampling &lab analysis

Yes butless thanFEC

Strain et al., 2002Davies et al., 2005

Eosinophilcounts

0.35 Concentration of cells in blood Lamb - Involvesbloodsampling &lab analysis

Yes Stear et al., 2002Davies et al., 2005

Fructosamineconcentrations

0.39 Concentration in plasma Lamb - Involvesbloodsampling &lab analysis

Yes Stear et al., 2001Davies et al., 2005

FootrotFootrot lesionscore

0.28 – 0.53 4 to 8-point scale based on degree ofinfection severity

Any Any Subjective No Skerman et al, 1988Raadsma et al., 1994

Footrot Gene-Marker Test(New Zealand)

genetic variation within the ovine MHCloci in the class II region, specifically atthe DQA2 gene

- - - Yes Hickford, 2000

MastitisSomatic CellCounts

0.04 – 0.24 Counts of epithelial and inflammatorycells (per ml) from a milk sample (usuallytaken on ‘test’ days, i.e. at regularintervals during lactation).

Ewe 1st lactationonwards

Timeconsumingand difficultin meatbreeds

Yes Conington et al., 2005

Breeding for enhanced flock fertility

77

Trait Av.Heritability

Definition Ram,ewe orlamb

Age ofmeasurement

Ease ofrecording

Expensiveto record

Key references

Ovulation rate 0.15 Number of corpora lutea on each ovary Ewe From firstoestrous

Laparoscopy Yes Safari & Fogarty, 2003

Fertility 0.08 Number of ewes lambing per ewe joined Ewe At lambing Easy No Safari & Fogarty, 2003Litter size 0.13 Number of lambs born per ewe lambing Ewe At lambing Easy No Safari & Fogarty, 2003Scrotalcircumference

0.21 Greatest diameter of the scrotal sac Ramlamb

Optimum 90-180days

Easy No Safari & Fogarty, 2003

Serving capacity 0.25 Rate at which rams attain successfulmatings when housed with estrousfemales

Ram From 14 months Timeconsuming

Yes,probably

Stellflug et al., 2006Snowder et al., 2002

Breeding for improved maternal ability and lamb survivalMaternal traitsGestation length 0.20 – 0.29 Days from joining to birth of lamb(s) Ewe First parity

onwardsEasy No Osinowo et al., 1994

Vatankhah et al., 2000Lambingease/length ofparturition

0.05 – 0.17 Interval between the first definite sign ofimpending parturition in the ewe to thebirth of a specific lamb.

Ewe During parturition Easy buttimeconsuming

No Cloete et al., 2002

Pelvic capacity - Mean pelvic dimensions Ewe - Involves CTscanning

Yes Bilbe et al., 2005

Ewe lamb-rearing ability

0.06 Ratio of lambs weaned to lambs born Ewe When lambs areweaned

Easy No Cloete et al., 2003

MaternalBehaviour Score

0.13(Lambe etal,2001)

0.09(Everett-Hincks etal., 2005)

5-point scale based on the distance a eweretreats from her lambs when theshepherd is tagging them (appendix 1)

Ewe When lambs aretagged

Easy No O’Connoret al., 1985Lambe et al., 2001

Maternalcooperation score

- 6-point scale based on active cooperationof the ewe post-partum (standing still,adopting a slightly hunched posture toenable access to the udder and nudgingthe lamb in a position to facilitatesuckling.

Ewe Straight afterparturition

Easy buttimeconsuming

No Cloete et al., 2003

78

Trait Av.Heritability

Definition Ram,ewe orlamb

Age ofmeasurement

Ease ofrecording

Expensiveto record

Key references

Period eweremains on ornear birth site

0.20 (just 1study)

Ewes regarded as having left their birthsites permanently after having movedaway more than 15m for more than 2h

Ewe Straight afterparturition

Easy buttimeconsuming

No Cloete et al., 2003

Milk score 0.08 – 0.26 6-point score based on udder size andudder milkiness (often divided into 3categories: ‘low’, ‘medium’ and ‘high’)

Ewe Straight afterlambing, 1st

parity onwards

Easy butsubjective

No Snowder et al.,2001a,bSawalha et al., 2005

Lamb traitsLamb survival 0.06-0.13 Survival time Lamb Birth to weaning

(and beyond ifdesired)

Easy No Sawalha et al., 2006

Time taken tostand and suck

0.08 – 0.12 Interval from birth to apparently suckling Lamb Birth Easy butrequirescarefulobservation

No Cloete et al (2002)

Cold resistance 0.3 – 0.7 Time taken for the lambs’ rectaltemperature to fall to 35 0C whenimmersed in a cooling water bath

Lamb Few days afterbirth

Easy No Samson and Slee, 1981Slee and Stott, 1986Slee et al., 1991

Breeding for other traitsLongevity 0.06-0.08 Days in the flock or days to final joining Ewe At culling Easy No Brash et al., 1994c

Conington et al., 2001Bone quality - Areas and density of spongy and compact

bone in the tibiaEwe Any age Involves CT

scanningYes Conington et al., 2004

Bodycomposition

- Prediction of depletion and repletion ofinternal and carcase fat and muscle

Ewe - Involves CTscanning

Yes Conington pers.comm.

Wool shedding - - Eweandram

- Easy No Conington, 1990Vipond, 2006

Temperament 0.23 Behavioural tests measuring approach andavoidance behaviour and degree ofanxiety in isolation

Any Any Timeconsumingand requiresspecialequipment

Yes Murphy et al., 1994Martin et al., 2004

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