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Livestock Science

Livestock Science 170 (2014) 142–149

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A comparison of the impact of behaviours performed by entiremale and female pigs prior to slaughter on skin lesion scoresof the carcass

Dayane Lemos Teixeira n, Laura Ann BoylePig Development Department, Animal & Grassland Research & Innovation Centre, TEAGASC Moorepark, Fermoy, Co. Cork,Republic of Ireland

a r t i c l e i n f o

Article history:Received 27 May 2014Received in revised form15 September 2014Accepted 29 September 2014

Keywords:BoarWelfareSkin lesionCarcassBruise

x.doi.org/10.1016/j.livsci.2014.09.02613/& 2014 Elsevier B.V. All rights reserved.

esponding author. Tel.: þ353 25 42254; faxail address: dayane.teixeira@teagasc.ie (D.L.

a b s t r a c t

The production of entire males is likely to increase with the introduction of a voluntary EUlevel ban on castration coming into effect in 2018. However the rearing of these animalsmay pose other challenges regarding welfare and production problems relating particu-larly to carcass quality. The aim of this study was to investigate whether there is arelationship between the aggressive and mounting behaviours performed by pigs in thefinal weeks prior to slaughter and skin lesion scores recorded on farm and on the carcass.A total of 70 entire male and 71 female pigs (Large White� Landrace) were housed in fivepens of each sex (mean of 14.170.74 pigs/pen) in the finisher house. On days �14 and�1 relative to slaughter (Day 0) pigs were individually weighed and skin lesions werescored according to severity. Posture and all incidences of harmful, aggressive andmounting behaviours were directly recorded in 3�2 h periods (8–10 h, 11–13 h, 14–16 h) on days �13, �9, �7 and �2. At the slaughterhouse, tail lesions, skin lesions andbruises were scored on all carcasses. Boars performed more aggressive (1.8 vs. 1.0aggression/pig/period; s.e.m. 0.22) and mounting behaviours (0.4 vs. 0.005 mounts/pig/day; s.e.m. 0.02) than gilts (Pr0.05). In general, postures were similar in both sexes(P40.05). On Day �1, boars had higher skin lesion scores than gilts (11.2 vs. 8.2; s.e.m.0.95; Pr0.05). Boars had higher skin lesion scores on the carcasses (1.9 vs. 1.3; s.e.m. 0.10;Pr0.05) and more fighting-type bruises (4.5 vs. 2.3; s.e.m. 0.35; Pr0.05) than gilts. Therewas no association between aggressive behaviour and skin lesions scored on farm on Day�1 (P40.05) but there were positive correlations between aggressive behaviour and skinlesions scored on the carcass (actor: r¼0.383, Pr0.001; recipient: r¼0.294, Pr0.001,respectively) and fighting-type bruises (actor: r¼0.442, Pr0.001; recipient: r¼0.297,Pr0.001, respectively). Skin lesions scored on the carcass were a more sensitive indicatorof aggressiveness and welfare of pigs than those recorded on the live animal. The resultsfrom this study reinforce the importance of on-line monitoring of carcass skin lesion inthe routine inspection procedures as a complementary tool to identify critical points alongthe slaughter chain and as an indicator of animal welfare on farm.

& 2014 Elsevier B.V. All rights reserved.

: þ353 25 42340.Teixeira).

1. Introduction

The main reason why male pigs are castrated is thepossible presence of boar taint in pork, but the removal oftesticular hormones also reduces aggression and sexual

D.L. Teixeira, L.A. Boyle / Livestock Science 170 (2014) 142–149 143

behaviour (Fredriksen et al., 2008). However, castrationcauses pain and discomfort (Llamas Moya et al., 2008) andtherefore raises ethical and welfare concerns. The produc-tion of entire males is likely to increase with the introduc-tion of a voluntary EU level ban on castration coming intoeffect in 2018 (Fredriksen et al., 2008; Fàbrega et al., 2013).The rearing of entire males may pose other challengesregarding welfare and production problems relating parti-cularly to carcass quality.

Growing pigs in commercial production systems per-form a variety of undesirable behaviours such as belly-nosing, tail- and ear-biting (Blackshaw, 1981; Breuer et al.,2005) and aggression (Andersen et al., 2000) which poserisks to pig welfare. In systems where entire males (i.e.boars) instead of castrates are produced the performance ofhigh levels of aggressive and mounting behaviour furtheraggravates the risk to welfare (Rydhmer et al., 2006; Boyleand Bjorklund, 2007; Hintze et al., 2013). Lameness is a riskwhen these behaviours are performed on fully slatted floors(Scott et al., 2006) and injuries such as lesions to the skincaused by the teeth during aggression (Turner et al., 2006)and the front legs during mounting also occur (Faucitano,2001). Bruises to the loin area are also seen in pigs comingfrom entire male production systems (Harley et al., 2014).Although the precise aetiology of loin bruising is unclear, itwould appear that pressure applied by the sternum of themounting pig to the loin area of the pig being mountedcould be involved, particularly when the behaviour isperformed by heavy pigs close to slaughter (L Boyle,personal communication). The ability to measure lesionsarising from these undesirable behaviours performed onfarm on the carcass would yield a valuable welfare diag-nostic tool (Harley et al., 2012a, 2012b, 2014). Therefore, theaim of this study was to investigate whether there is arelationship between the aggressive and mounting beha-viours performed by pigs in the final weeks prior toslaughter and skin lesion scores recorded on farm and onthe carcass.

2. Materials and methods

The study was carried out during summer 2013 at theTeagasc integrated 250 sow research herd based at Moor-epark, Fermoy, Co. Cork, Ireland. Pigs were assembled intogroups at weaning (28 days of age) based on sex and size andthe group composition was unaltered through to slaughter.In the pre-transport pens, trial animals were randomlymixed with 36 female and male non-trial pigs from thesame farm, and were transported to an abattoir 100 kmaway, in a conventional two tier lorry (stocking density waswithin the legislative requirement of 0.42 m2/pig (CouncilRegulation, 2005). Pigs were CO2 gas stunned after c. 1 h inlairage with solid concrete walls and floors (water wasavailable but no food). The work was approved by theTeagasc Animal Ethics Committee (TAEC 24/2013).

2.1. Animals and housing

A total of 70 entire male and 71 female pigs, born fromLarge White� Landrace sows, were housed in five pens ofeach sex (n¼5 female pen, n¼5 male pen; mean of

14.170.74 pigs/pen) in the finisher house. Pens(2.32 m�4.73 m) had fully slatted, concrete floors andwere furnished with chains hanging from the pen wallsand a single rubber enrichment device (EasyFix™ RubberProducts, Ballinasloe, Co. Galway, Ireland) suspended atpig height in the middle of the pen. All animals were ear-tagged with a unique number and marked on the lumbararea using animal marking spray. In addition to the herdidentification tattoo (i.e. ‘slap number’), all pigs alsoreceived an individual tattoo on the shoulder for identifi-cation of the carcasses.

Pigs had ad libitum access to a standard, commercial,pelleted finisher diet (Vigour, Nutec, Naas, Co. Kildare,Ireland) in a multi-space feeder (75 cm length�60 cmhigh�30 cm deep) without divisions which was replen-ished twice a day (10:00 h and 16:00 h). Water wasavailable ad libitum from a single bite-drinker in eachpen. Data collection took place on farm for two weeksprior to slaughter.

2.2. Measurements on farm

2.2.1. PerformanceOn days �14 and �1 relative to slaughter (Day 0) pigs

were individually weighed and average daily gain wasdetermined by the difference between weight on Day �1and Day �14 divided by 14 (i.e. the number of days).

2.2.2. BehaviourBehaviour was directly recorded in 3�2 h periods

(8:00–10:00 h, 11:00–13:00 h, 14:00–16:00 h) on days�13, �9, �7 and �2. Two trained observers watcheddifferent pens simultaneously and they were balancedacross sex and pens. Observation times were also balancedacross sex and pens thus the observations for each penwere distributed equally across the recording periods.

Scan sampling: every 3 min, the posture (Table 1) ofeach pig in the pen was recorded and then the observermoved on to the next pen according to the schedule, untilthe two hour observation schedule was completed, thisyielded 192 scan samples per pen.

All-occurrence sampling: after the postural behaviour ofthe pigs in each pen was recorded by scan sampling, thepigs were observed continuously until 3 min had elapsedwith all incidences of harmful, aggressive and mountingbehaviours (Table 1) being recorded during this time. Intotal, each pen was observed for 576 min. The identity ofthe pigs involved in these interactions was also recorded.

2.2.3. Skin lesion scores

On Days �14 and �1, after the pigs were weighed, skinlesions were scored according to severity on the back, leftand right hind quarters, side, belly, shoulders, neck andears. Scores were summed to yield a total lesion score foreach pig. Lesions were scored as follows: (1) superficial orpale red lesion; (2) red lesion; (3) deep red or extensivelesion. Additionally, scores from the ears, neck andshoulders (front of body), and back and hindquarters (rearof body) were summed separately as lesions to these areas

Table 1Description of behaviours collected during observations. The ethogram was based on O’Driscoll et al. (2013).

Description

Instantaneous scan samplingPosture

Lie active Pig lying with eyes open and interacting with something or some penmateLie inactive Pig lying and not performing any behaviour, with eyes closed or openSit Pig sitting like a dog (dog-sitting position)Stand Pig standing upright

All-occurrence samplingHarmfulTail, ear orbelly

Pig directs oral attention to either the tail, ear or belly of another pig. Behaviours were recorded separately for each body part

AggressiveHeadknocks

Knocking against the head of another pig by a vigorous upward thrust of the head

Fights Mutual pushing parallel or perpendicular, ramming or pushing of the opponent with the head, with or without biting in rapidsuccession. Lifting the opponent by pushing the snout under its body (Stewart et al., 2008)

Mounts2 Placing hooves on the back of a standing pen-mate (Scott et al., 2006)

D.L. Teixeira, L.A. Boyle / Livestock Science 170 (2014) 142–149144

are thought to reflect predominately agonistic and mount-ing behaviour, respectively.

2.2.4. Locomotory ability

On Day 1, when pigs left the weighing scales theirlocomotory ability was assessed using aspects of theprocedure of Main et al. (2000) and including an evalua-tion of the pig’s standing posture and gait. Pigs were givena score of 0 (not lame) to 5 (severely lame, cannot stand).

2.3. Post-mortem measurements

2.3.1. Tail lesion and loin bruises scoresCarcass data were collected by two people on the day of

slaughter. At the slaughter line, one person was positionedafter the dehairing point and before the carcass-splittingpoint. At this point, carcasses (hanging by both hind legs)were identified by the individual tattoo and both tail(Fig. 1) and loin bruises (Fig. 2) were scored as perHarley et al. (2012b, 2014), respectively. Both scores wereconducted by the same person throughout the experi-ment. At the weighing scales, a second person recordedthe line “kill” number of each study carcass to later accesscarcass cold weights.

2.3.2. Skin lesion and bruise typesAfter being dressed, carcasses were brought to a chill

room where they were kept at 2–3 1C, with air velocity of0.5 m/s. At this point, skin lesions were assessed as perVelarde and Dalmau (2012) according to the WelfareQualitys (2009) protocol. The carcass was divided into fiveparts: front (from the head to the back of the shoulder);middle (from the back of the shoulder to the hind-quar-ters); hindquarters; legs (from the accessory digit upwards)and back (the spinal column and adjacent muscles from theneck to the butt of the tail). Both sides were assessed. Eachpart was scored as follows: (0) no visible skin damage, onlyone lesion greater than 2 cm or lesions smaller than 1 cm;(1) between two and 10 lesions greater than 2 cm; and (2)any wound which penetrated the muscle tissue, or morethan 10 lesions greater than 2 cm. The scores for the five

parts of the carcass were combined in one score: (0) allbody parts with a score of zero; (1) at least one body partwith a score of one; (2) a part with a score of two or more;and (3) more than one part with a score of two.

The assessment of carcasses for bruises was carried outby a second person. Bruises were evaluated by registeringtheir location (similar to location scored for skin lesions),size and shape and then classified according to type. Basedon the Institut Technique du Porc photographic standards(ITP, 1996), the bruises were classified as fighting- (r10 cmlength, linear and tramline and concentrated in highnumber in the front and hindquarter parts), mounting-(Z10 cm length, linear and concentrated in the back) andhandling-type (all sizes of circular, mottled and irregulardistributed along the body). The number of each type ofbruise was counted on both sides of the carcass.

2.4. Statistical analysis

Data were analysed using the Statistical Analyses Sys-tem (SAS Institute Inc., 1988). Data were tested for normal-ity prior to analysis by examination of box and normaldistribution plots. Initial and final body weight, averagedaily gain and carcass cold weight were analysed using theMixed procedure. Sex was inserted into the model as afixed effect and pen as experimental unit.

Behaviour samplings recorded by continuous observa-tion were analysed using the Mixed procedure. The num-ber of occurrences of aggressive and harmful behavioursper pig was averaged for each period, providing threevalues per group per day. The average value for eachperiod was also adjusted for the number of pigs in eachpen. Sex was included in the model as a fixed effect andpen as experimental unit. Both mixed models did notinclude interaction terms as they were not relevant.Because of the infrequency of mounting behaviours, thefrequency of this behaviour was averaged to provide asingle mean value for each day per pen. Sex was includedin the model as a fixed effect, experimental day as arepeated measure and pen as experimental unit.

The frequency of postures was also analysed using theMixed procedure. Sex was included in the model as a fixed

0 1 2 3 4

Fig. 1. Tail lesion score for carcasses. (0) No evidence of tail biting; (1) healed or mild lesions; (2) evidence of chewing or puncture wounds, but no evidenceof swelling; (3) evidence of chewing or puncture wounds with swelling and signs of possible infection; (4) partial or total loss of the tail.

0 1 2

Fig. 2. Loin bruising scoring system for carcasses. (0) No evidence of loin bruising; (1) moderate loin bruising; (2) severe or extensive loin bruising.

D.L. Teixeira, L.A. Boyle / Livestock Science 170 (2014) 142–149 145

effect, experimental day as a repeated measure and pen asexperimental unit. The effect of group size on all variableswas not relevant and all mixed models included interac-tion terms where relevant. When significant effects werefound, Tukey’s test was used to establish pairwise differ-ences. Statistical differences were considered significant atPr0.05. Data are presented as means7standard errors.

Non-parametric methods were used to analyse the skinlesion and locomotion scores of animals on farm as well astail lesions, loin bruises, skin lesions and bruise types onthe carcasses due to the non-normal distribution of thesedata. Wilcoxon scores (rank sums) were calculated and aKruskal–Wallis test was used to test for statistical differencesbetween sexes (NPar1Way procedure). Pearson and Spear-man’s correlation coefficients were calculated between vari-ables in accordance with the normality of the data, using thecorrelation procedure in SAS. For the correlation calculations,a behaviour index was created per animal as the meanfrequency of each behaviour.

3. Results

3.1. Measurements on farm

3.1.1. PerformanceAverage daily gain was lower in female than in entire

male pigs (738740 vs. 918738 g/day; Po0.001) and

females were lighter than entire male pigs at the end ofthe study (99.0370.582 vs. 100.7070.604 kg; Po0.05).However, there was no effect of sex on carcass cold weight(77.3470.401 kg; P40.05).

3.1.2. Behaviour

The effect of sex on the behaviour of pigs is described inTable 2. There was an effect of the period of the day on allbehaviours observed; however sex only affected aggressiveand mounting behaviours. Entire males performed moreaggressive and mounting behaviours than female pigs(Pr0.05). With the exception of standing, there were nointeractions between period of the day and sex (P40.05;data not shown). In general, there was no effect of sex onstanding behaviour (23.2772.86%; P40.05) but entiremales spent more time standing than female pigs in period2 (11:00 to 13:00 h; Pr0.05). No differences were foundin periods 1 (08:00 to 10:00 h; P40.05) and 3 (14:00 to16:00 h; P40.05; Fig. 3).

3.1.3. Skin lesion scores

There was no effect of sex on the total and front of bodyskin lesion scores recorded at the beginning of the study(Day �14 prior to slaughter; P40.05). However, entiremales had higher skin lesion scores for the rear of the body

Table 2Effect of sex and period of day on the behaviour (mean7s.e.m.) of entire male (i.e. boar) and female pigs.

Sex Period Sex�period

Female Entire male s.e.m. P-value P-value P-value

Lying actived (%) 5.44 4.63 0.77 ns o0.001 nsLying inactive (%) 65.98 63.88 2.82 ns o0.001 nsSittingd (%) 6.90 6.63 0.61 ns o0.001 nsStanding (%) 21.68 24.86 2.44 ns o0.001 0.02Harmful behavioursa,d(n) 0.57 0.62 0.09 ns o0.001 nsAggressive incidentsb (n) 1.03 1.76 0.22 o0.01 o0.001 nsMountingc (n) 0.005 0.40 0.02 o0.001 – ns

ns¼Non-significant. Harmful and aggressive behaviours are expressed in mean±s.e.m. of the number of events per pig per period of observation. Mountingbehaviour is expressed in mean±s.e.m. of the number of events per pig per day of observation.

a Harmful behaviour included tail, ear and flank bites.b Aggressive incidences include head knocks and fights.c The incidence of mounting behaviour was averaged to provide a single mean for each day per pen, so the effect of period was not analysed.d In cases where transformed data were used in the analysis, P-values refer to transformed data, but means and standard error were calculated using

raw data.

ax

bycx

ax

bx bx

0

10

20

30

40

1 2 3Stan

ding

beh

avio

ur (%

)

Period of day

Female Male

Fig. 3. Effect of gender and period on standing behaviour of pigs(means7s.e.m.). Period 1: 8:00–10:00 h; Period 2: 11:00–13:00 h; Per-iod 3: 14:00–16:00 h). Different letters “a,b” represent significant differ-ences (Pr0.05) between period of day within sex. Different letters “x,y”

represent significant differences (Pr0.05) between sex within periodof day.

D.L. Teixeira, L.A. Boyle / Livestock Science 170 (2014) 142–149146

compared to female pigs (Pr0.05) on this inspection day(Table 3). On the day prior to slaughter (Day �1), entiremales had higher total skin lesion scores than female pigs(Pr0.05) but there was no effect of sex on the front andrear of body lesion scores separately (P40.05). The increasein skin lesion scores between days was not significant forboth sexes (P40.05).

3.1.4. Locomotion scores

There was no effect of sex on locomotion scores(1.3270.11; P40.05).

3.2. Post-mortem measurements

3.2.1. Tail lesion and loin bruise scoresThere was no effect of sex on tail lesion (0.4770.06) or

loin bruising scores (0.6270.06; P40.05).

3.2.2. Skin lesion and bruise typesCarcass skin lesion scores and fighting-type bruises

were higher in entire male than female pigs (Pr0.05)

but there were no effects of sex on mounting andhandling-type bruises (Table 3).

3.3. Correlations between variables measuredThe numbers of aggressive and mounting behaviours

both performed (actors) and received (recipient) werepositively correlated with average daily gain (aggression– actor: r¼0.282, Pr0.001; recipient: r¼0.300, Pr0.001and mounting – actor: r¼0.213, Pr0.05; recipient:r¼0.212, Pr0.05). Final body weight was also positivelycorrelated with the number of aggressive and mountingbehaviours performed (aggression: r¼0.230, Pr0.01 andmounting: r¼0.207, Pr0.05). The number of aggressive(r¼0.505, Pr0.001) and mounting (r¼0.663, Pr0.001)behaviours performed (actor) were positively correlatedwith the numbers of these behaviours received. A signifi-cant correlation was found between skin lesion scoresrecorded on the farm prior to slaughter (i.e. Day �1) andboth final body weight and carcass cold weight (r¼0.225,Pr0.01 and r¼0.223, Pr0.01, respectively).

The number of aggressive behaviours performed andreceived were not correlated with skin lesion scoresrecorded on the farm on the day prior to slaughter (Day�1); however, this behaviour was positively correlatedwith carcass skin lesion scores (actor: r¼0.264, Po0.01;recipient: r¼0.302, Po0.001) and fighting-type bruises(actor: r¼0.442, Pr0.001; recipient: r¼0.297, Pr0.001).Finally, there was no association between skin lesionsscored on the farm and at the slaughterhouse (r¼�0.093,P40.05).

Mounting behaviours were not associated with skinlesions scored on farm (actor: r¼0.126, P40.05; recipient:(r¼0.134, P40.05). However, the number of mountsreceived was associated with carcass skin lesion score(actor: r¼0.157, P¼0.08; recipient: r¼0.187, Po0.05). Noassociation was found between the number of mountsreceived and carcass loin bruises (r¼0.035, P40.05) ormounting-type bruises (r¼�0.034, P40.05). Tail lesionscores were not associated with the number of tail bitingincidents received (r¼�0.059, P40.05) or with carcasscold weight (r¼�0.023, P40.05). Locomotory ability was

Table 3Differences between sexes in the median (interquartile range) skin lesion scores measured on farm on Day �14 and Day �1 prior to slaughter and on thecarcass (i.e. at the slaughterhouse).

Skin lesion scores Female Entire male

Mean Median (interquartile range) Mean Median (interquartile range)

Day �14Total 7.70 6.00 (7.00) 9.11 7.50 (6.00)Front of body 4.10 4.00 (4.00) 5.14 4.00 (4.00)Rear of body 1.42a 1.00 (2.00) 2.02b 1.50 (3.00)Day �1Total 8.2a 7.00 (7.00) 11.17b 9.00 (9.00)Front of body 4.35 4.00 (4.00) 6.21 4.00 (6.00)Rear of body 1.86 1.00 (2.00) 2.24 1.50 (4.00)Carcass 1.3a 1.00 (1.00) 1.88b 2.00 (2.00)Bruise typesFighting 2.25a 1.00 (3.00) 4.45b 3.00 (6.00)Mounting 0.05 0.00 (0.00) 0.02 0.00 (0.00)Handling 1.70 1.00 (2.00) 1.98 1.00 (2.00)

ab Within a row means lacking common superscript letters differ; Pr0.05.

D.L. Teixeira, L.A. Boyle / Livestock Science 170 (2014) 142–149 147

not correlated with the final body weight (r¼0.133,P40.05).

4. Discussion

The findings of this study confirm other findings thatentire males in single-sex groups perform more aggressiveand mounting behaviours compared to female pigs (Rydhmeret al., 2006; Boyle and Bjorklund, 2007; Vanheukelom et al.,2012; Hintze et al., 2013) and confirm that the high incide-nce of these behaviours in groups of male pigs is reflectedin higher skin lesion scores in these animals prior to andpost slaughter.

In general, there were no differences in activities betweensexes, except that entire male spent more time standingbetween 11:00 and 13:00 h than female pigs. Although feedwas available ad libitum, the feeders were replenished withfresh feed at 10:00 h which provoked interest in feedingamongst all pigs. Considering that there is a higher prevalenceof fights (Rydhmer et al., 2006; Boyle and Bjorklund, 2007;Thomsen et al., 2012) and mounts (Fredriksen et al., 2008)during feeding between entire males, this could indicate thatentire male pigs took longer to calm down afterwards. It ispossible that higher levels of standing (activity) in the maleswould have been confirmed with 24 h observations of thepigs’ activity budgets (Vanheukelom et al., 2012).

Aggressive interactions are a source of stress (de Jonget al., 1999) which has negative implications for pig welfare.Unsurprisingly, given their higher levels of testosterone(Giersing et al., 2000) there was a higher prevalence ofaggressive behaviour in entire male compared to femalepigs (Vanheukelom et al., 2012). However, there was a highfrequency of aggression in both sexes which likely reflectsdeficiencies in their housing environment (Olsson et al.,1999). Pigs were stocked at densities permissible under EUlegislation but were in fully slatted pens with minimalenvironmental enrichment which is associated with highfrequencies of aggression (Thomsen et al., 2012). Although itwas not very high, the positive correlation between thenumber of aggressive behaviours performed and received

and between both the actor and recipient and their respec-tive average daily gains, is an indication that fast-growingpigs are more aggressive than slower-growing pigs (Pittset al., 2000; Rydhmer et al., 2006). Fighting behaviour tendsto be more prolonged and serious when the weight differ-ences between pigs are small (Andersen et al., 2000).Therefore, it is probable that heavy weight pigs predomi-nantly fought other heavy weight pigs and the greater levelof injury reflects their greater strength and larger canineteeth (Turner et al., 2006).

Mounting behaviour is part of the pigs’ normal beha-viour repertoire. Both sexes perform sexual behaviour,although higher incidences are seen in male than in femalepigs (Rydhmer et al., 2006; Boyle and Bjorklund, 2007;Thomsen et al., 2012; Hintze et al., 2013) which is consistentwith the findings of this study. Heavier pigs performedmore mounts than lighter pigs in the present study,probably as a consequence of testicular steroids stimulusthrough approaching to puberty (Giersing et al., 2000).

Lameness or leg injuries, caused by frequent mountingbehaviour, could be a problem in the production of entiremales, especially those in single-sex pens (Rydhmer et al.,2006). However, in agreement with Vanheukelom et al.(2012) and Hintze et al. (2013), the results of this study didnot find difference between sexes in locomotory ability.Also, there was no relationship between final body weightand locomotory ability, which is different from findings forsows (Calderón Díaz et al., 2013).

Skin lesion scores are a useful measure of the outcomeof aggression in pigs (Turner et al., 2006). The skin lesionscore of the front of the body is positively associated withthe proportion of time spent in reciprocal fighting, howeverpigs that retreat from a fight are more susceptible to lesionslocated around the rear of the body (Turner et al., 2006).Unsurprisingly, and in accordance with previous findings(Rydhmer et al., 2006), females had fewer skin lesions thanentire male pigs which confirms the findings on aggressivebehaviour. Two weeks prior to slaughter, entire malespresented more skin lesions on the rear of body comparedto female pigs, which may originate from bites directed at a

D.L. Teixeira, L.A. Boyle / Livestock Science 170 (2014) 142–149148

fleeing opponent (Turner et al., 2006) or lesions frommounting (Rydhmer et al., 2006). However the differencebetween sexes embraced all of the body on the day prior toslaughter and, therefore, it is possible that entire malesretaliate from aggressions more often at the end of thefattening period. Also, it is likely that this at least partiallyreflected the dramatic reduction in space allowance in thepens that would have been associated with growth rates ofbetween 700 g and 900 g per day during that period(Turner et al., 2000). In accordance with Turner et al.(2006) there was a positive correlation between skin lesionsrecorded on the farm and body weight which is in agree-ment with the finding that aggressive behaviour and finalbody weight were positively correlated.

There was no correlation between the number of aggres-sive behaviours performed or received and skin lesion scoresrecorded on the farm; nor between the number of mountsperformed or received and the same skin lesion scores.Hintze et al. (2013) also found no association between theperformance of mounting behaviour or being mounted andmounting scratches. In contrast Fredriksen et al. (2008)found a positive correlation between the behaviour indexof each pig and skin lesion scores recorded in the herd. It ispossible that a better relationship between behaviour andskin lesion scores might have been found if the duration ofthe behaviour observations was longer or if the way that thebehaviour was recorded might have been more sensitive, e.g.included the intensity or duration of the fights.

The absence of a sex effect on tail lesion scores was notexpected since male sex increases the risk of tail lesions(Harley et al., 2012b). However, most pigs are kept inmixed sex pens on Irish farms which might explain thedifferences between this and the studies by Harley et al.(2012b, 2014). Loin bruising also affected both sexesequally which is in accordance with a previous survey inthe Republic of Ireland (Harley et al., 2014).

As expected and as per the finding for scores on the liveanimal, carcass skin lesion scores were higher in entire malecompared to female pigs (Vanheukelom et al., 2012). Therewas no difference between sexes in mounting-type andhandling-type bruises, which reinforces the results on theloin bruising scores and indicates that all groups werehandled similarly both on farm, during transport to theslaughterhouse and in the lairage. On the other hand, thefighting-type bruise score was higher in entire male thanfemale pigs. Bruises are an important source of informationabout pig welfare (Faucitano, 2001) and the detection ofbruises at the slaughterhouses may provide useful informa-tion about traumatic situations for the animals during thepre-slaughter period and the extent of sub-optimal welfare(Strappini et al., 2011). This finding suggests that the welfareof entire male pigs was compromised compared to the femalepigs. Furthermore, such bruising may necessitate trimmingwhich results in downgrading of the value of the carcass andrepresent an economic problem for the industry (MLC, 1985).

In contrast to skin lesions scored on the live animal (i.e.on farm), both the actor and recipient of aggressive andmounting behaviours was associated with skin lesionsscored on the carcass suggesting that this score might bea more sensitive indicator of aggressiveness and welfare ofpigs on farm. In accordance with Fredriksen et al. (2008),

there was no correlation between the skin lesion scores ofpigs in mixed sex groups scored on farm and at theslaughterhouse. Unfortunately, Vanheukelom et al. (2012)did not conduct skin lesion scoring of entire males andfemale pigs in single-sex groups on the farm.

5. Conclusion

The findings of this study confirm that entire male pigs insingle-sex groups perform more aggressive and mountingbehaviour compared to female pigs, and confirm thehypothesis that the incidence of these behaviours in bothsexes is associated with increased skin lesion scores. Skinlesions scored on the carcass were a more sensitive indicatorof aggressiveness and welfare of pigs than those recorded onthe live animal. The results from this study reinforce theimportance of on-line monitoring of carcass skin lesion inthe routine inspection procedures as a complementary toolto identify critical points along the slaughter chain and as anindicator of animal welfare on farm.

Conflict of interest

There are no conflict of interest issues concerning thissubmission.

Acknowledgments

The authors acknowledge the financial support pro-vided by the Irish Government’s National DevelopmentPlan 2007-2013 for Dayane Teixeira (Department of Agri-culture, Food and the Marine’s Competitive ResearchProgramme—RSF 11/S/107). Great thanks to Tómas Ryan(staff of the Teagasc Pig Development Department, PDD),Vincent Rafter (manager of the abattoir), Nienke vanStaaveren (Masters student) and Maiwenn Bourdoulousand Anaëlle Laravoire (work placement students at thePDD) for their help with data collection.

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