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EB1601

Bull Selection andBreeding Soundness

Evaluation forthe Beef Producer

Donald D. Nelson

Cooperative ExtensionCollege of Agriculture and Home Economics

Washington State University

Contents

Introduction .................................................................................................................................. 3Understanding and Using Expected Progeny Differences (EPDs) ................................................ 3Breeding Soundness Evaluation ................................................................................................... 4Other Selection Considerations .................................................................................................... 7Economic Impact of Bull-to-Female Ratio ................................................................................... 8Natural Breeding vs Artificial Insemination ............................................................................... 9References ................................................................................................................................... 11

Tables

1. Male reproduction evaluation for breeding soundness ........................................................... 72. Bull cost per heifer .................................................................................................................... 9

The average female only produces one calfper year, having very little genetic impacton the herd.

The best way to evaluate the potentialgenetic value of a bull is through a soundset of performance records and the use ofexpected progeny differences (EPDs). EPDsallow us to do a more accurate job of com-paring bulls within breeds than previousmethods.

You should first determine the currentstrengths and weaknesses of your cow herd.Next, establish some specifications for thetraits you want in the bulls you ultimatelyselect (e.g., birth weight, weaning weight,yearling weight, milk production, etc.). Thenconsult the sire summaries of the breedsyou are interested in and select the siresthat meet these specifications.

Understanding and UsingExpected Progeny Differences (EPDs)

Expected progeny differences (EPDs) areused to estimate how the future progeny ofa bull will compare to the progeny of otherbulls within a particular breed. EPDs arereported in pounds for birth weight, weaningweight, yearling weight, maternal weaningweight and maternal milk production. Scrotalcircumference EPDs are given in centimeters.

Each bull listed in a breed’s sire evaluationreport is compared to all the other bulls listed.For example, Bull A has an EPD for yearlingweight of +30 pounds with an accuracy valueof 0.80 and Bull B has an EPD for yearlingweight of +5 pounds with a similar accuracyvalue. If these two bulls are bred to enoughcows in your herd, you could expect Bull

IntroductionThere is a saying regarding bull selection:

“Visual analysis tells you what a bull appearsto be. His pedigree tells you what he ought tobe. His performance and progeny tests tell youwhat he actually is.”

You should consider several factors whenselecting a bull for your operation: breed, size,desirable traits, complementarity in a cross-breeding program and marketing strategy forthe offspring. From an economic standpoint,reproduction is 10 times as important ascarcass quality and 5 times as important asgrowth rate.

In recent years, frame size has beenemphasized as a desirable trait. The economicvalue of greater than average frame size tothe commercial cattle producer is questionable.Martin Jorgensen of Ideal, South Dakota, whohas been feeding, processing and marketingbeef through his own branded beef programfor the last several years, stated that, “An inchof height is worth about $.03 and an inch ofthickness is worth about $50 per head.” As acommercial beef producer, you are in businessto sell pounds of red meat, not inches ofheight and bone.

You select and purchase bulls for geneticimprovements that will help you achieve thegoals of your breeding program. Researchindicates that as much as 80-90% of theprogress made in a breeding program comesthrough proper bull selection. If naturalservice is used, each bull should sire approxi-mately 25 calves per breeding season. Ifartificial insemination is used, one bull couldtheoretically sire all of the calves producedby your herd in a given breeding season.

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Bull Selection and BreedingSoundness Evaluation for the

Beef ProducerDonald D. Nelson

A’s progeny to have a +25 pound advantagein yearling weight over Bull B’s progeny.

The information used to calculate an EPDmay be based on any combination of: indi-vidual performance, pedigree and progenyand grand progeny performance information.In addition, sire EPDs are more accurate thananything previously available because theyaccount for the following factors:

1) Genetic value of cows a bull is bred to2) Environmental differences affecting

contemporary groups3) Quality of other sires in the

contemporary group4) Genetic trend.Once a bull has progeny, less emphasis

is placed on the less quantitative pedigreeinformation. The sire’s own performance andthe performance records of his progenybecome the major determinants of the EPD.

Accuracy values indicate the predictabilityof EPDs and are an abbreviated method ofexpressing an EPDs reliability. Accuracyvalues range from 0.0 to 1.0. As accuracyapproaches 1.0, the EPD is more reliable andcan be expected to change less in the futureas more progeny data are accumulated.

Accuracy may be categorized into low,medium and high reliability as follows: low,

0.0-0.50; medium, 0.51-0.75; high, 0.76-1.0.EPDs are used to decide which bulls areselected while accuracy values suggest howextensively the bulls should be used. Bullswith favorable EPD values and correspond-ingly high accuracy values can be used withthe confidence that they will geneticallyimprove the herd.

Breeding Soundness Evaluation (BSE)Once you have selected a bull with the

desired genetics, you must be sure that thisbull is capable of causing pregnancy in acow herd. Each and every bull needs to havea breeding soundness evaluation (BSE) everyyear, 30-60 days before the start of thebreeding season. It has been reported thatmore than 10% of yearling bulls are eithersterile or subfertile and 4% of proven siresdevelop serious fertility problems betweenbreeding seasons. To reduce the likelihoodof introducing venereal diseases into yourherd, we recommend that you purchasevirgin bulls.

Much of the material in the followingdiscussion of the breeding soundness evalua-tion comes from the Beef ImprovementFederation’s Guidelines for Uniform BeefImprovement Programs.

Figure 1. Three scrotal shapes commonly seen in beef bulls. They are the straight-sidedscrotum (A), the normal scrotum (B) and the wedge-shaped scrotum (C). Scrotal shape Bis the most desirable. (Coulter 1987).

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A B C

by an individual who can properly evaluatetesticular tone as it relates to testicular func-tion. Deviations from normal testicles varyfrom extremely fibrotic to a soft, flaccidconsistency. Conditions such as testiculardegeneration or hypolasia (atrophy) andorchitis (inflammation of the testis) affect theconsistency and size of the testicles and resultin abnormal sperm production. During severewinters, it is not uncommon for a bull’sscrotum to become severely frostbitten orfrozen with a resultant decrease in fertility.

b) Rectally examine accessory sexglands. This is an examination of thereproductive organs located in thepelvic region. Abnormalities of theaccessory sex organs (prostate, seminalvesicles, ampullae and ductus deferens)are not uncommon and are oftenaccompanied by poor semen quality.If an active inflammatory process ispresent, white blood cells will be foundin the ejaculate, varying from a few toalmost 100% of the sample.

c) Examine extended penis andprepuce. The external genitaliashould be examined with great care;the penis is palpated through theexternal sheath and by protruding itmanually. Prolapse of the prepuce isoccasionally found, more often in theBrahman and Brahman-derivedbreeds. Unless there are lesions on theprolapsed membrane, the prolapse doesnot interfere with mating. However,the exposed membrane is predisposedto injuries.

At this time, you may take diagnosticpreputial samples to determine the presenceor absence of campylobacteriosis or tricho-moniasis. The penis and prepuce should beexamined for any structural abnormalitiesor adhesions when the semen sample iscollected.

Upon erection, the penis should comefrom the sheath in a straight line with thebody of the bull. In Australia a defect called“spiral deviation of the penis” has beenidentified (Coulter 1987). A report fromAustralia indicates that bulls in 60% of herds

Examining bulls for breeding soundnessbefore the breeding season will detect mostbulls with potential fertility problems. Thisexamination should be performed by aveterinarian who has had significant experi-ence in bovine herd health and fertilityevaluation of bulls, or by other experienced,competent personnel. However, even with thebest personnel, current techniques cannotaccurately predict degrees of fertility. BSEs arereally a screening process used to assessprobable bull fertility. Results from an actualbreeding season remain the only true testof a bull’s fertility.

Breeding SoundnessEvaluation Guidelines1. Physical examination. Do this beforecollecting semen. This will cull bulls withundesirable physical characteristics or abnor-malities before you make useless attempts atcollection.

a) Palpate scrotum and testes. Bullshaving a normally shaped scrotumwith a distinct neck generally have thebest testicular development (Figure 1,Bull B). Testes are located in thescrotum because sperm can only beproduced within a narrow temperaturerange, several degrees cooler thaninternal body temperature. Normalscrotal anatomy permits effectivetemperature regulation.

Bulls with straight-sided scrotums oftenhave only moderate testicle sizes (Figure 1,Bull A). The straight-sided neck of the scrotumis generally due to fat deposits that willprobably impair proper thermoregulation,particularly in the summer. As bulls matureand lose fat, they often develop a more nor-mal-shaped scrotum.

Wedge-shaped scrotums are pointedtowards the bottom and tend to hold thetestes close to the body wall (Figure 1, Bull C).Bulls with this scrotal configuration haveundersized testes that seldom produce semenof adequate quality. Bulls with wedge-shapedscrotums should be avoided.

Palpate the scrotum and testicles, notingposition and consistency. This should be done

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examined were affected, and that 1% ofhorned bulls and 16% of polled bulls had thedefect. This condition results in a significantreduction in the bull’s ability to service cowsbecause he cannot accomplish insertion. Inbulls where 100% of their mounts were af-fected, pregnancy rates were as low as 3%.Spiral penile deviation is probably just asprevalent in North America.

Spiral deviations are usually found inbulls 3-6 years old. This condition cannot bediagnosed at the time of electroejaculation. Infact, electroejaculation can induce a similardeviation of the penis that may not occur atall during natural service. Watch the breedingactivity of your bulls to make sure they do nothave this defect. Spiral deviation is moder-ately heritable. It can be diagnosed by allow-ing a bull mount several estrus-synchronizedheifers and carefully observing the results.

Record any injury or abnormality asacceptable or unacceptable. If the bull isunacceptable, have the examiner explainwhy. Bulls with gross deficiencies or abnor-malities detected by physical examinationshould be culled.2. Scrotal circumference. Scrotal circum-ference and testicular size are directly relatedto sperm production in dairy and beef bulls.Since the testicles are composed of 75-80%seminiferous epithelial cells and these cellsform spermatozoa, it is logical that the largerthe testicles, the greater the bull’s ability toproduce sperm and produce pregnancies. Inaddition, bulls with small testicles tend toproduce a higher percentage of abnormalsperm.

As the scrotal circumference increases,motility and percent normal sperm increaseand sperm abnormalities decrease. Scrotalcircumference has been shown to be a moreaccurate predictor of when a bull reachespuberty than either age or weight, regardlessof breed or breed cross (i.e., an average of 27.9cm.). Yearling bulls should have a scrotalcircumference of at least 30 cm.

Record the actual measurement of scrotalcircumference in centimeters, and age of the

bull at time of measurement.Scrotal circumference is highly heritable

and has a high positive genetic correlation toage of puberty of the bull’s daughters. Studieshave shown that for each additional 4.0 cm.of scrotal circumference above the breed orherd average, one can expect a 1.0 cm.increase in the scrotal circumference of maleoffspring and 15.44 days earlier puberty infemale offspring. The use of a sire with aboveaverage testicular size (scrotal circumference)for his age and breed will result in femaleprogeny that reach puberty at a younger age,cycle more regularly and consequently havegreater potential lifetime productivity.

Scrotal circumference is the most usefullinear measurement currently taken on beefcattle.3. Semen evaluation. Under field conditions,the semen sample is usually collected byelectroejaculation. All bulls do not respondwell to the electroejaculator, and may notproduce representative samples.

The two most important things to look forin the semen are the proportion of sperm thatare motile and the structure or morphology ofthe sperm. Procedures for scoring motility andmorphology are found in the Proceedings ofthe 1976 Annual Meeting of the Society ofTheriogenology. A third factor, the concentra-tion of sperm in an ejaculate, may not beaccurately measured when the semen sampleis collected by electroejaculation.

A semen sample should only be evaluatedfor motility under field conditions if thetemperature of the sample has been keptconstant from the time of collection until thetime of examination under the microscope.Small portable slide warmers are available forthis purpose. The presence of urine in thesample will greatly reduce motility. Heat, coldor chemical contamination of the collectionapparatus can immobilize spermatozoa.

The appearance of an increased numberof abnormal sperm in the ejaculate is areflection of lesions of the testes and/or theexcurrent duct system. Some sperm abnor-malities (e.g., acrosomal and nuclear) are

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heritable and bulls exhibiting these abnor-malities should be culled. A bull should haveno more than 20% abnormal sperm. If a bullhas a sperm abnormality greater than 80%,he will probably be infertile.

The scoring system for predicting potentialbreeding soundness of bulls prepared by theSociety of Theriogenology (1976) incorporatesscrotal circumference, sperm motility, andsperm morphology (Table 1). New and betterscoring systems are likely to emerge over timefrom the Society and other sources and werecommend their use.

The results of semen evaluation of beefbulls 11-13 months old are often difficult tointerpret. For example, semen quality inyoung bulls has been shown to improve, oftendramatically, for up to 16 weeks following theonset of puberty. Test the semen of youngbulls at 15 or 16 months of age to avoid thepotential early culling of a bull that mayhave adequate semen quality 2 months later.

Positive results from a semen evaluation,even in yearling bulls, indicate a moderate tohigh probability of acceptable fertility, whilenegative results are not conclusive, particu-larly if the bulls involved are young or sexu-ally rested. Reevaluate bulls with poor semenquality every 3-4 weeks. If the results do not

improve, you can be fairly sure that the bullis infertile and should be culled. All bullsshould be tested before every breeding seasonas injuries or other problems may havereduced the bull’s semen quality since theprevious evaluation. A breeding soundnessevaluation performed by a veterinarianusually costs $25-35 per bull.

Other Selection Considerations1. Body condition. Bulls should haveenough body condition to be strong withsome reserves of energy in the form of fat.Overfat bulls have decreased fertility anddecreased stamina for mounting and seekingcows in heat. A Canadian study reported thatfeeding high energy diets to young Herefordbulls damaged their sperm producing abilityto the extent that several bulls in the studywere sterile.2. Feet, legs and joints. Good feet and legsare essential if a bull is to travel long distancesover rough terrain and service cows success-fully. Particular attention should be given tothe manner in which the bull moves. Thestride should be free with no signs of lame-ness. Abnormal conformation of the rearlimbs (i.e., sickle-hocks and post-legged) isespecially detrimental to the bull used in

Table 1. Male Reproduction Evaluation for Breeding Soundness. 1

Morphology 2 Scrotal circumference 3 Scoring System 4

Classification

Very goodGoodFairPoor

MotilityScore

No.

201210

3

Source: Beef Improvement Federation 1990.1 Examination as recommended by Society for Theriogenology, revised, September 1976.2 Spheriods: Less than 05/HP field = Occasional = +05% primary abnormality

05/ to 15/HP field = Few = +15% primary abnormality15/ to 25/HP field = Many = +25% primary abnormality

+25/HP field = Multitudes = +35% primary abnormality.3 Scrotal circumference data based on data from Angus, Charolais, Hereford, and Simmental breeds.4 Based on scoring system totals, satisfactory potential breeder has 60-100 points; questionable potential breeder has 30-59 points; and unsatisfactorypotential breeder has 0-29 points.

Primaryabnor-

malaities

1010-1920-2929

Totalabnor-

malaities

2526-3940-5960

Score

No.

402410

3

— – Percent – —

12-14months

old

3530-35—30

— – — – — – — – Cm – — – — – — – —

15-20months

old

3731-37—31

21-30months

old

3932-39—32

30+months

old

4033-40—33

Score

No.

4024—10

Motility

201210

3

Morph-ology

402410

3

Score No.

Scrotalcircum-ference

4024—10

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natural service. Long hooves and cornsshould be trimmed 4-6 weeks before thebreeding season.3. Eyes. Pinkeye or cancer eye hinder a bull’svision and reduce his breeding effectiveness.Bulls that are blind in one eye present adanger to the people handling them and tocows they are attempting to sevice.4. Pelvic measurements. Some purebredbreeders perform pelvic measurements onyearling bulls because of this trait’s highheritability (50-55%). The hypothesis is thatbulls with larger pelvic areas will sire daugh-ters with larger pelvic areas which shouldresult in a reduction in calving difficulty.However, pelvic measurements and otherphysical measurements (e.g., pelvic slope)have generally served as poor predictors ofcalving difficulty.

As a general rule, larger-framed cattlehave larger pelvic areas and also producecalves with heavier birth weights. Calf birthweight and age of dam at calving are themost important factors affecting calvingdifficulty.5. Libido. Libido, or sexual activity, andsemen production in bulls apparently have norelationship, so it is possible to get goodsemen from bulls with low libido and viceversa.

Mickelsen (1990) observed that the servingcapacity of a group of bulls is positivelycorrelated with the proportion of cows exhibit-ing estrus in a herd. He cited a study in whichmounting activity was recorded for 7 1/2hours when bulls, in groups of 3, were putwith 114 head of heifers. Bulls in the highserving capacity group (10.3 services/bull)had an 81% first-service conception ratecompared to 56.7% for the bulls in the lowserving capacity group (2.3 services/bull).

Studies have shown that both a lownumber of services and a very high numberof services were associated with poor fertility.Low numbers or no services during testing islikely predictive of low breeding activity underfield conditions. Very high serving activitymay have resulted in the depletion of spermreserves.

Differences in libido in bulls are due togenetic as well as environmental factors.Several studies have shown that the dominantbulls in a group often sire the largest numberof calves (Mickelsen 1990). However, if thedominant bulls happen to be subfertile, thiscould actually result in a reduced number ofpregnant females. In a group of bulls withvarying ages, social ranking affects a bull’sserving capacity. Therefore, do not mixyearling and 2-year-old bulls with older bulls.

Economic Impact of Bull-to-FemaleRatio

In most parts of the country, the typicalbull-to-female ratios used by cow-calfproducers are from 1:15 to 1:30. Increasingthe efficiency of natural mating offers enor-mous potential for lowering the costs ofproduction.

Colorado State University recently com-pleted a study designed to determine theoptimal bull-to-female ratio required formaximum reproductive performance on bothestrus synchronized and naturally cyclingheifers. Four treatments were used : treatment1 included 200 nonsynchronized heifers and 2bulls/100 heifers (bull-to-female ratio of 1:50);treatment 2 involved 200 synchronized heifersand 2 bulls/100 heifers (bull-to-female ratio of1:50); treatment 3 involved 200 synchronizedheifers and 4 bulls/100 heifers (bull-to-femaleratio of 1:25) and treatment 4 involved 200synchronized heifers and 6 bulls/100 heifers(bull-to-female ratio of 1:16). Total length ofthe breeding season was 28 days.

Results of this study indicate that the costsof production can be reduced by lowering thebull-to-female ratio. Treatment 1 (2 bulls/100naturally cycling heifers) resulted in an 82%pregnancy rate. However, the results of thisstudy also indicate that there is a limit to howfar bulls can be extended when utilizingestrus synchronization. Treatment 2 (2 bulls/100 synchronized heifers) had a 77% preg-nancy rate. Treatments 3 (1:25) and 4 (1:16),both synchronized, resulted in pregnancyrates of 83% and 84%, respectively. Treatment

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4 had a 3-day advantage of day of conceptioncompared to treatment 3.

The bull cost per pregnant heifer wascalculated using the following assumptions.Yearling bulls, purchased for $1750, would beused for 4 breeding seasons before beingsold for $800. This resulted in an annualdepreciation cost of $238 ($1750 - $800 =$950 ÷ 4). Annual feed costs were $200,veterinary costs were $25 and there was anopportunity cost on the investment of $102($1750 + $800 = $2550 ÷ 2 = $1275 x 0.08).This is a total bull cost of $565 per year.Table 2 shows the effect of different bull-to-female ratios on bull costs per pregnantheifer. The cost of estrus synchronization inthis study was $3.70 per heifer, and is notincluded in the bull cost per pregnant heiferfigures.

The results of this study indicate thatmost ranchers could lower the bull-to-femaleratio used, maintain their herd’s productivityand lower their bull costs per pregnant fe-male. However, if you use a lower bull-to-female ratio, a breeding soundness examina-tion performed 30-60 days before the breedingseason is critical to success.

The Colorado researchers are planning torepeat this experiment, but will use artificialinsemination (AI) instead of natural mating

in the 1:16 bull-to-female ratio treatment.The use of AI has the potential of reducingthe breeding costs even more than loweringthe bull-to-female ratio.

Natural Breeding vsArtificial Insemination

While natural service is, and probablywill remain, the primary form of breeding inmost cow-calf operations, increasing the useof artificial insemination (AI) may increasegenetic improvements. For the commercialcow-calf producer, a good place to begin usingAI is in breeding yearling replacement heifers.These heifers are usually fed and handledseparately from the mature cow herd and youdo not have to deal with the added complica-tion of nursing calves.

The use of AI offers the following advan-tages to both purebred and commercial cow-calf breeders:

1. It should reduce the bull cost perpregnant female; eliminates the year-round expense and hassle of keepingand handling bulls. AI may notcompletely eliminate the use of naturalbreeding. You may still need clean-upbulls, but the total number of bullsrequired will be reduced.

2. You can use outstanding, proven bulls

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* Bull cost/hfr. exposed equals total bull cost/yr. divided by the number of females exposed (e.g., $565 ÷ 50 hfrs. =$11.30).** Bull cost/ hfr. pregnant equals bull cost/hfr. exposed divided by the pregnancy rate (e.g., $11.30 ÷ 0.82 =$13.78).Source: Healy, et al. 1990

Table 2. Bull Cost Per Heifer.

Treatment

Nonsynchronized1

Synchronized234

Bull-to Femaleratio

1:50

1:501:251:16

Bull costhfr. exposed*

$11.30

$11.30$22.60$35.31

Pregnancyrate

82%

77%83%84%

Bull cost/pregnant hfr.**

$13.78

$14.68$27.23$42.04

at modest prices and get maximumgenetic improvements in your herd. Inthree generations, 87.5% of the geneticsof your herd trace back to the sires ofthose three generations.

3. By using superior AI bulls, you canrapidly improve the economicallyimportant traits of calving ease,weaning weight, average daily gain,carcass quality and maternal ability.

4. The risk of introducing harmfulrecessive traits, such as dwarfism,double muscling, mule foot or marblebone is significantly reduced due tothorough sire selection and progenytesting.

5. Using AI usually results in an improvedlevel of management because morecomplete records are kept. This improvesreplacement heifer selection andproduction and feeding management.

6. The calving season can be shortened,resulting in a heavier and more uniformcalf crop.

7. Venereal diseases cannot be introducedor transmitted when using disease-freesemen.

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ReferencesAmerican Breeders Service. “AI Management

Manual.” Division of S.R. Grace &Company. DeForest, Wisconsin. 1983.

Beef Improvement Federation. Guidelines forUniform Beef Improvement Programs.Sixth edition. Oklahoma State University,Stillwater, Oklahoma. May 1990.

Brinks, James S. “Scrotal Circumference andIts Potential Usefulness.” Angus Journal.February 1985.

Brownson, Roger. “Breeding SoundnessExamination of Beef Bulls.” Angus Journal.April 1985.

Coulter, Glenn H. “Evaluating and Managingthe Herdsire for Reproduction.” AgricultureCanada Research Station, Lethbridge,Alberta. 1987.

Healy, V.M., G.W. Boyd, R.G. Mortimer andJ.R. Piotrowski. “Lowering Production Cost:Investigating the Optimal Use of BullPower.” National Conference: LoweringBeef Cattle Production Costs. ColoradoState University, Fort Collins, Colorado.October 5-6, 1990.

Mickelsen, W. Duane. “Breeding SoundnessExamination of the Bull: Fact or Fiction.”Unpublished paper. School of VeterinaryMedicine. Washington State University,Pullman, Washington. 1990.

Merck Veterinary Manual. “BreedingSoundness Examination of the Male.”Sixth edition. Edited by Clarence M.Fraser, et al. Merck & Co., Inc. Rahway,New Jersey. 1986.

Proceedings of the 1976 Annual Meeting ofthe Society of Theriogenology. Society ofTheriogenology, Association Building, 9thand Minnesota, Hastings, NE 68901

Ott, Randall S. “Breeding SoundnessExamination of the Bull: Semen Collectionand Evaluation.” Illinois ProfessionalTopics. 9:3. 1983.

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Donald D. Nelson is an Extension Beef Specialist at Washington State University.

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COOPERATIVE EXTENSION

Introduction

Selection decisions in the beef industryhave been fostered by the developmentand delivery of Expected ProgenyDifferences (EPD) for a wide variety oftraits and across all major US beefbreeds. Since the early 1970’s, EPDshave been used by seedstock andcommercial beef producers to makegenetic change in their herds. Today,EPDs are widely accepted across theindustry and are used frequently byproducers making seedstock selectionand purchase decisions. The degree ofconfidence in an individual animal’sEPDs is described numerically by acomputed value called ‘Accuracy.’Accuracy values in the US are scaledreliabilities and range from 0 to 1representing the amount of informationused to compute the EPD. An animalwith accuracy values near zero has verylittle data available for evaluation whilean animal with accuracy of 0.99 has avery large amount of informationevaluated.

Improvements in EPD accuracy havehistorically been driven by phenotypicrecord collection directly on the trait ofinterest or on indicator traits. For traitslike stayability or length of productivelife, the evaluation of a sire’s daughtersis typically completed long after the bullhas been removed from production. Forother traits like carcass weight, marblingscore, and rib-eye area, the animal must

This factsheet was developed as part of USDA NIFA grants # 2013-68004-20364

#2011-68004-30367#2011-68004-30214

be harvested or ultrasound informationcollected as indicator trait data. Thereare costs associated with collecting andprocessing phenotypic data. To achievehigh levels of accuracy a great deal ofprogeny and/or grand progeny data mustbe included in the evaluation.

Timing is Everything

Accuracy values for bulls purchased bycommercial producers as yearlings willbe low. In most cases only the bull’s ownperformance records for traits observedbefore sale day and pedigreeinformation will be included in his EPDcalculations. For the maternal traits likeheifer pregnancy, stayability andmaternal milk no daughters will havebeen produced so only pedigreeestimate or interim EPDs will beavailable, and these EPD have lowaccuracies. In order to improve theaccuracy of the EPDs of yearling bullsanother source of information is needed.

Genomic information gives an accuratepicture of what alleles an offspringinherited from its parents in the form ofSingle Nucleotide Polymorphisms(SNP), and has always held the promiseto increase the accuracy of EPD. Thispromise has finally been realized forthose breeds that had breed-specifictraining populations that enablegenotypic information to be translatedinto genetic merit estimates (i.e.Molecular Breeding Values (MBV)) that

1 of 4

How DNA Testing Will Affect the Accuracy of EPD Information

Bob Weaber, Kansas State University, bweaber@k-state.eduMatthew Spangler, University of Nebraska, mspangler2@unl.edu

2014 - 12

Dr. Darrh Bullock

Dr. Jared Decker

Dr. Megan Rolf

Dr. Matthew Spangler

Dr. Robert Weaber

Dr. Alison Van Eenennaam

2 of 4

can be incorporated into genomic-enhanced EPD calculations. Studieshave shown that genomic informationcannot be accurately translated intoMBV for complex traits (i.e. thosecontrolled by many genes) in theabsence of breed-specific trainingpopulations.

One key advantage of MBV is that thisinformation can be garnered early in thelife of the animal thus enabling anincrease in the accuracy of EPDparticularly on young animals, whichhave not yet produced progeny. Ideally,MBV data should be used to increasethe accuracy of the EPDs of younganimals prior to any selection decisions(performance based culling) made at theseedstock level. Seedstock genetictrends and subsequent genetic flow tocommercial producers will only beimproved if seedstock producers actuallyuse the genomic-enhanced EPDs tomake selection decisions for animalsthat will be retained as breeding animalsand offered for sale to commercialproducers. Genotyping a group ofanimals immediately before sale after allselection has been completed doesnothing to improve genetics of thepopulation; it only fosters marketingefforts and only allows for betterselection decisions within a highlyselected subset of the sale offering.

The US Beef Industry has witnessedconsiderable evolution in terms of thegenomic tests available in the marketplace. The tests that are currently being

included in EPD are comprised of50,000 (50K) SNP, although somebreeds utilize 80K panels and some aremoving towards reduced (e.g. 20K)panels with the aid of imputation(essentially using information from thepopulation to “replace” missinggenotypes). The research community iscommonly using 50K, 80K or 770Kgenomic tests for discovery of “novel”traits (i.e. feed efficiency, diseasesusceptibility).

Implementation

The underlying question commonlyasked by producers is “Do genomic testswork?” It is critical to understand thatthis is a somewhat ambiguous question,as the true answer is not binary (i.e. yesor no). The important question to ask is“How well do genomic tests work?”, andthe answer to that question is related tohow much of the genetic variation thegenomic test explains. The benefit willbe dependent upon the proportion ofgenetic variation (%GV) explained by agiven genomic test. The %GV is equal tothe square of the genetic correlationmultiplied by 100. Table 1 shows therelationship between the geneticcorrelations (true accuracy), %GV andBeef Improvement Federation (BIF)accuracy. BIF accuracy is the standardfor all U.S. beef breeds.

Molecular Breeding Values should notbe thought of as a separate independentpredictor of genetic merit, but rather as apotentially useful indicator that is

How DNA Testing Will Affect the Accuracy of EPD Information • www.eBEEF.org • 2014-12

This factsheet was developed as part of USDA NIFA grants # 2013-68004-20364

#2011-68004-30367#2011-68004-30214

Table 1. The relationship between true accuracy (r), proportion of genetic variation explained (%GV), and Beef Improvement Federation (BIF) accuracy.

r (true accuracy) %GV BIF0.1 1 0.0050.2 4 0.0200.3 9 0.0460.4 16 0.0830.5 25 0.1320.6 36 0.2000.7 49 0.286

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correlated to the trait of interest.Combining the genomic information withtraditional sources of EPD informationincreases the accuracy of the resultinggenomic-enhanced EPD and this hasthe potential to increase the rate ofgenetic change by both increasing theaccuracy of selection, and decreasingthe generation interval. This lattercomponent of the breeder’s equationwould be particularly impacted if youngsires are used more frequently as aresult of the increased confidence intheir genetic superiority due to addedgenomic information.

Figure 1 illustrates the benefit ofincorporating genomic information into agenomic-enhanced EPD on accuracy(on the BIF scale) when the MBVexplains 40% of the genetic variation(GV), which is synonymous with an r2

value of 0.4. The darker portion of thebars shows the EPD accuracy before theinclusion of genomic information and thelighter colored portion shows theincrease in accuracy after the inclusionof the MBV into the EPD calculation. Asthe %GV increases, the increase in EPD

accuracy becomes larger. Additionally,lower accuracy animals benefit more fromthe inclusion of genomic information andthe benefits decline as the EPD accuracyincreases. Regardless of the %GVassumed here, the benefits of includinggenomic information into EPD dissipatewhen EPD accuracy is between 0.6 and0.7. On the other hand, when %GV is 40,an animal with 0 (zero) accuracy couldexceed 0.2 accuracy with genomicinformation alone. This would becomparable to having approximately 4progeny for a highly heritable trait or 7progeny for a moderately heritable trait(Table 2).

Although the American SimmentalAssociation (ASA) was the first toaugment their Warner Bratzler ShearForce EPD with genomic information,several other breeds have adopted thistechnology and others are in the processof collecting sufficient records to developbreed-specific training populations.Research has shown moderate to highgenetic correlations between severaltraits of interest and MBV in multiplebreeds when the animals the test is used

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Figure 1. Increase in accuracy from integrating genomic information that explains 40% of the genetic variation into Estimated Breeding Values (EBV).

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on are within the same breed as thetraining data set used to develop theMBV. However, it has also been clearlydemonstrated that when a MBVdeveloped in one breed is used in adifferent breed, even a closely relatedbreed (e.g. Angus and Red Angus), thegenetic correlation drops substantially.

This shows the unfortunate breedspecificity issues surrounding thesetools. This is consistent with otherresults that show the predictive power ofMBV begin to erode as the geneticdistance between the training and target(or evaluation) populations increase.This would be expected overtime asanimals in the training data used todevelop the MBV become more distantlyrelated to animals currently beingevaluated with the genomic test. This iswhy these tools need to be “re-trained”or “re-calibrated” periodically.

Some breeds do not have the luxury ofimmediately having thousands ofgenotyped animals for use in developingbreed-specific training populations.Consequently, the use of a robustacross-breed set of genomic predictionequations would be beneficial. Thereare two primary methods of constructingan across-breed training data set: poolpurebred animals from multiple breedsor use crossbred animals. The firstoption requires the use of EPD,corrected for differences in accuracy, as“phenotypes” for training similar to the

within breed scenario with the exceptionof correcting for breed effects in themodel. The second option requires theuse of adjusted phenotypes (correctedfor contemporary group effects, sex,etc.) to train the genomic predictors.Although pooling animals of differentbreed together in training can be useful,it only helps if it will be used in breedsthat were represented in the trainingdata.

Conclusions

Genomics and the correspondingMarker-Assisted or Genomic-EnhancedEPD, have become a reality. Within-breed genomic predictions based on50K genotypes have proven to addaccuracy, particularly to young bulls, forseveral traits. The push going forwardwill be the adoption of this technology byother breed associations. Furthermore,methodology related to the use of thistechnology in crossbred or compositecattle is critically needed, . The crux ofadoption will be getting commercial bullbuyers to see the value in, and thus payfor, increased EPD accuracy. There isstill a need to collect and routinely recordphenotypic information by seedstockproducers. Commercial producersneed to realize that EPDs, andeconomic index values, are thecurrency of the realm for beef cattleselection. Genomic technology onlymakes these tools stronger, it doesnot replace them.

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Table 2. Approximate number of progeny needed to reach accuracy levels (true (r) and the BIF standard) for three heritabilities (h2).

Developing a mating system thatoptimizes profitability for a commercialbeef operation can be tricky. There aremany factors that must be consideredincluding: heterosis, breed selection,selection tools, market,environmental/management conditionsand simplicity. To complicate the issuethese factors do not functionindependently and there are interactionsto consider. As with all aspects of beefcattle management a game plan shouldbe developed and implemented with theultimate goal of profitability.

Market

The revenue generating components ofthe beef operation should be aconsideration for almost all decisionsthat will be made and developing amating system is no exception. Thetypical sources of revenue for mostcommercial operations are calvesmarketed in various ways, and cull cowsand bulls. Decisions that are made indeveloping mating systems can havehuge impacts on both of these sourcesof revenue.

Calves

How the calf crop is marketed should beone of the major factors determining amating system. This can vary fromselling weaned calves at the stockyardsstraight off the cow to retaining

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ownership and being paid on carcassvalue. When considering these twoextremes it is easy to see that theproducers selling weaned calves wouldneed to focus on reproduction andfactors affecting weaning weight; theproducers selling carcasses will alsohave to consider reproduction, butcarcass quality and weight are now thevalue determinants for the product beingsold. The relative importance ofmaternal versus paternal traits is greatlyinfluenced by when and how the calveswill be marketed.

Another consideration would be whetherthe end target is commodity beef or abranded product. With brandedproducts there may be breed, colorand/or production specifications thatmust be met. All of these factors can beaddressed with the proper matingsystem.

Cows and Bulls

The marketing of cows and bulls is oftenoverlooked when making managementdecisions, but can have a large impacton the operation’s net income. Factorssuch as mature size and replacementrate determine how much income isgenerated through the sale of cullanimals, but both of these factors havesome significant consequences to beconsidered. If replacement rates arehigh this is likely due to low reproduction

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Mating Systems in Commercial Beef Cattle Operations

Darrh Bullock, University of Kentucky, dbullock@uky.edu

2014 - 5

Dr. Darrh Bullock

Dr. Jared Decker

Dr. Megan Rolf

Dr. Matthew Spangler

Dr. Robert Weaber

Dr. Alison Van Eenennaam

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rates since culling open cows is typicallypracticed in commercial operations; ifthat is the case then emphasis should beplaced on improving the fertility of theherd within the constraints of the givenenvironment. The other factor of maturesize is typically a secondary effect ofgenetics for calf growth; high growthcalves typically develop into largemature cows and are produced by largebulls. The management implication tobe aware of is that larger cows havehigher maintenance requirements.

Heterosis

Heterosis typically has the greatestimpact on lowly heritable traits such asreproduction and longevity. These traitshave importance in all beef operations,but likely have a greater relative impacton a cow/calf operation that is sellingcalves at auction rather than one that isretaining ownership and being paid oncarcass value. The potential to improveweaned weight per cow exposed byapproximately 20% throughcrossbreeding versus straight breedingis a powerful incentive to implementcrossbreeding in the mating system forthe cow/calf producer. With the limitedimpact of heterosis on carcass traits,some retained ownership operationsmay be inclined to forego crossbreeding.Although the impact of reproduction andlongevity may be lessened somewhat ina retained ownership operation, they stillhave a significant impact on profitabilityand should not be ignored.

.

Breed Selection

The genetic trends of the major beefbreeds in the US indicate that the breedsare more similar for most productiontraits than they were historically. Growthand milk have dramatically increased inthe British breeds making them moresimilar to the Continental breeds andlikewise the Continental breeds haveplaced negative pressure on birth weightto reduce the gap with the Britishbreeds. The impact on carcasscharacteristics is less clear, but mostbreeds have applied positive pressure toimprove marbling. It is critical to assessthe positive and negative characteristicsof the breeds being considered and findthe balance that is optimal to meetingyour market and management plans.

Selection Tools

Once many of the other decisions aremade regarding the mating systemselection tools can be used to fine tunethe process. Management, marketingand crossbreeding decisions tend to bebroad based and not targeted atindividual aspects. Selection tools onthe other hand can be used to create thespecific animal to fit a particularenvironment and be marketed in aspecific way. The traits underconsideration for change are typicallyclassified in one of two ways:quantitative or qualitative traits.

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Quantitative Traits

Quantitative traits are traits that arecontrolled by multiple genes and greatlyinfluenced by the environmentalconditions, including management.These are typically the production traits,for example: growth traits, milking ability,fertility and carcass traits. The relativeimpact of the genetic contribution to atrait is described by the heritabilityestimate. These estimates theoreticallyrange from 0 to 1 with higher valuesindicating a greater influence by additivegenetics on the trait. For most traits inbeef cattle these estimates range from.05 to .50 (See Table 1).

Table 1. Heritability estimates for somecommon beef traits.

For most economically relevantquantitative traits Expected ProgenyDifferences (EPD) are computed by therespective breed associations. With theincorporation of genomics informationthis selection tool is becomingincreasingly accurate in young animals.With improved accuracies from genomictests it is more critical than ever thatproducers use EPD correctly, which formany traits means selecting for theoptimum rather than the maximum.

A selection tool that has been developedto assist in the process of optimizing foreconomic importance is selection indices.A selection index allows the producer toselect bulls based on an assortment oftraits that have been economicallyweighted to indicate the bull that has theoptimum combination of traits to producethe most profitable calves. Selectionindices greatly simplify the selectionprocess for commercial producers, butcare should be taken to be certain thatthe index selected includes the traits thatare of economic importance to theiroperation and that theirmanagement/environmental andmarketing conditions are similar to thoseused to develop the index.

Qualitative Traits

Qualitative traits are those that aretypically controlled by one pair of genesand are not greatly influenced by theenvironment. Examples of typicalqualitative traits in beef cattle are coatcolor and the horned/polled condition.When considering these types of traits itis important to understand the inheritancemode of the trait. For the two exampletraits, coat color and horned/polled, inmost cases is controlled by simplerecessive inheritance. There are factorssuch as diluter genes for coat that cancomplicate things, thereforeunderstanding how the genes work andinteract is important when a specificoutcome is desired.

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Trait h2

Calving Interval .05

Female Fertility .04

Weaning Weight .35

Milking Ability .35

Marbling .45

Mature Weight .50

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Environmental/ManagementConditions

Mating systems have to do with findingthe right genetics, but this must bedone in the context of the environmentinto which the cattle are going to beplaced. Matching the genetic potentialof the herd to the production level ofthe operation is one of the most criticalsteps of developing a mating system.Failure to recognize limitations in theresources being provided to the cattlecan result in reduced performance;conversely, selecting genetics thatunder utilize resources results ininefficiencies and lost revenue.

The two management constraints thattypically influence the breedingprogram are labor and nutritionlimitations. The amount of time (labor)that is dedicated to the cow herdduring calving will have a significantimpact on the level of calving ease thatwill be required of the bull. If labor islimited during this time, and particularlyif heifers are calving for the first time,then a greater level of calving easedirect will be required of the bull.

The nutrition level being provided tothe herd may be a little more difficult toassess, but is critical to determinewhat level of production is appropriatefor the herd. The mature size of thecows and level of milk being producedwill greatly influence the maintenancerequirement of the herd. Cows with

high maintenance requirements, butlimited available nutrients are not agood match and will result in a loss ofcondition with possible negative effectson fertility. Low producing cows in anutrient rich environment can becomeoverly fat, potentially reducing fertilityand certainly not getting the level ofproduction appropriate for theresources being utilized.

Simplicity

As with most things, the simpler wecan keep our mating system the morelikely we are to stick to it. Having agood understanding of all the topicsdiscussed previously will be necessaryto develop an appropriate matingsystem, but once in place it should berelatively easy to maintain. The matingsystem should be target directed, butflexible to meet variable conditions.Environmental fluctuations are a fact oflife in many parts of the US andadapting to change is often necessary;early weaning can be necessary, butunless it is a permanent change itshould not have an impact on the nextherd sire that is purchased. The samecan be said about market conditions,even if your breeding program isdirected towards retained ownership.Sometimes market conditions warrantselling earlier than expected; these areshort-term financial decisions, butthese short term fluctuations shouldnot be the grounds for dramaticallyredesigning the mating system.

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Division of Agricultural Sciences and Natural Resources • Oklahoma State University

ANSI-3289

Oklahoma Cooperative Extension Fact Sheets are also available on our website at:

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Oklahoma Cooperative Extension Service

Megan RolfAssistant Professor

Tom SmithExtension Educator, Agriculture

Purchasing bulls and replacement females from a repu-table breeder pays; however, many forego using this information to choose the best animals because it can be overwhelming. Knowing how to properly work through a sale catalog is paramount to success in choosing a herd bull, cleanup sire, or replacement heifers. Understanding the expected progeny difference (EPD) and performance measures listed in sale catalogs can seem daunting, but these ten tips will help make the process easy and painless:

Before the Sale 1. Decide on your traits of interest and your “deal break-

ers.” Before requesting sale catalogs, it is a good idea to

make some decisions about which traits are a priority in your production system. Consider the amount of labor and resources (forage, grain, etc.) available and decide which traits might be limiting in your environment. For example, if you work off the farm or ranch, you may not have the labor resources available to monitor and assist with calving problems, so calving ease EPDs would be a priority. Another example would be limited forage avail-ability, making the selection of animals with moderate growth rates, smaller mature size, and moderate milk production (i.e. moderate yearling weight and milk EPDs) your focus. Also consider when you will sell the cattle, as this will dictate which output traits are important. If selling at weaning, the weaning weight EPD may be of utmost importance, whereas if you are retaining ownership, some selection on carcass traits would be warranted. If raising your own replacements, make sure to place some selec-tion emphasis on maternal traits. If you have a terminal breeding system and will not keep replacements, you do not need to place any emphasis on maternal traits for bull selection.

Once important traits are identified, decide which ones are “deal breakers.” These will be traits that would reduce the ability of the cattle to fit your environment and production system. For example, if you are keeping replacements for a harsh environment, you may select only sires in the top 15 percent of the breed for calving ease and no higher than breed average for mature height/weight (or yearling weight) and milk production. You may wish to keep your desired EPD ranges for the traits you

Ten Tips for Utilizing A Cattle Sale Catalog

are interested in on a small card in your wallet to refer back to both looking through the catalog and later at the sale.

2. Decide on a breed to achieve your goals. If you have not already selected a breed, consider

which breeds will best fit your production system and selection goals that you developed in tip 1. It is easier to identify a breed with the strengths you are looking for than to try and find bulls or females within a breed which has poor performance (on average) for a trait you are interested in improving. This is where appropriate use of crossbreeding to capitalize on breed complementar-ity can be valuable. To help select a breed, consider the information in Figure 1. When buying females, it is a good idea to consider taking advantage of heterosis by purchasing crossbred females. Crossbred females have, on average, better fertility, 600 additional pounds of cumulative weaning weight and almost one additional calf over their lifetime when compared to purebred cows.

3. Do a Background Check. Getting the catalog in advance, most likely through

the mail, will give you ample time to look through the performance information and other pertinent material. The ultimate goal is to narrow down the number of bulls which need to be visually examined by using their performance and EPD data. Thoughtful completion of this process takes time, so it is imperative to obtain the catalog well in advance of the sale. Animals that have pedigrees indicating that they are closely related to large numbers of animals (i.e. out of the same sire) within your herd should be eliminated to avoid inbreeding depression and expression of genetic defects. It may also be useful to visit the ranch where you wish to buy a bull or female so that you can examine their management practices and view the cowherd. If the breeder’s herd is managed similarly to your own and has a cowherd that looks like you want yours to look, it is probably a good place to source genetics. If you intend to retain replacement females, closely examine the dams of your potential purchases. In addition to conformation and mature size, inspect the udder attachment and teat size, as these factors influence the longevity of animals in your herd. Also request to see

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their production records (which is often called a “dam summary”) to verify the dams’ fertility and performance of other offspring.

4. Examine guarantees, delivery, and other information. Most cattle sold through a seedstock sale will have

associated guarantees through their breed association, through the producer themselves, or both. This informa-tion is frequently listed in the front of the sale catalog. Make sure that the animals are guaranteed to be breeders and that a breeding soundness examination has been performed on all bulls. If you are considering non-virgin bulls, make sure they tested negative for trichomoniasis. In addition, consider pickup (whether they will hold the cattle or if they must be picked up sale day) and delivery information (trucking arrangements, etc.). Some larger producers may also have buyback or other marketing opportunities for calves sired by their bulls. If you have questions about the guarantee, delivery procedures, or other questions about the cattle, do not hesitate to contact the seedstock producer or the sale management. They have a vested interest in making sure that potential buyers are knowledgeable about the services being offered to them. An example of what this information may look like is included in an excerpt from the OSU Cowboy Classic Sale (Figure 2).

5. Eliminate those animals which do not have accept-able performance for your deal breakers.

When beginning to sort through the performance data, any animals possessing characteristics that are not consistent with your production goals should be eliminated from consideration. Those traits and characteristics identified as deal breakers should be given comparatively more weight than other goals in the breeding objective. For example, you may wish to eliminate any bulls that you would not consider “calving ease” if he is to be used on heifers. If cows with large mature size or high milk production are a deal breaker in your environment, you may wish to choose animals that are at or below breed average for mature size EPDs (or alternatively yearling weight for those breeds that do not have mature size

Figure 2. Sample of OSU's Cowboy Classic Sale terms and conditions.

Figure 1. Table from NBCEC Sire Selection Manual, 2nd Edition.http://www.nbcec.org/producers/sire.html

Growth Percent Age Breed a,b Rate and Retail at MilkGroup Mature Size Product Puberty Production

Jersey X X X XXXXLonghorn X XXX XXX XXAngus XXX XX XX XXXHerford XXX XX XXX XXRed Poll XX XX XX XXXDevon XX XX XXX XXShorthorn XXX XX XXX XXXGalloway XX XXX XXX XXSouth Devon XXX XXX XX XXXTarentaise XXX XXX XX XXXPinzguaer XXX XXX XX XXXBrangusXXX XX XXXX XXSanta Gertrudis XXX XX XXXX XXSahiwal XX XXX XXXXX XXXBrahman XXX XXX XXXXX XXXNellore XXX XXX XXXXX XXXBraunvieh XXXX XXXX XX XXXXGelbvieh XXXX XXXX XX XXXXHolstein XXXX XXXX XX XXXXXSimmental XXXXX XXXX XXX XXXXMaine Anjou XXXXX XXXX XXX XXXSalers XXXXX XXXX XXX XXXPiedmontese XXX XXXXX XX XXLimousin XXX XXXX XXXX XCharolais XXXXX XXXX XXXX XChianina XXXXX XXXX XXXX X

a Adapted from Cundiff et al. 1993.b Increasing number of X's indicate relatively higher levels of trait.

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Figure 3. Search results from a North American Limousin Foundation Sire Selector tool.

EPDs) and milk EPDs. Breed averages should be listed on each breed’s website, in the sire summary from the association, or may be listed in the catalog itself. Percentile ranks can be obtained from every breed association’s website.

6. Identify the animals within your optimal EPD range for your traits of interest.

After animals inconsistent to environmental and production concerns have been removed (the deal breakers), identify the animals that have EPDs within optimal ranges for the other selection criteria. Good ways to identify what EPDs may be optimal include decision support tools (such as the Angus Optimal Milk Module or Colorado State’s ERT Tool, for example) or EPD percentile ranks in each breed’s sire summary. With “deal breaking” animals already removed, simply select for EPDs with the most favorable values for the traits in your selection criteria. Remember that multiple-trait selection is essential, but the more traits being selected, the harder it is to find animals that meet all your require-ments and the less genetic progress you will make in any one trait. For example, a sire selector tool returned only 10 results when the selection criteria were top 25 percent for CED and WW and below the top 30 percent for MA and 40 percent for YW (selecting for high calving ease and weaning weight while limiting milk production and mature size).

7. Rank the bulls according to how well their EPD profile fits your production system.

After eliminating deal breakers and identifying per-centile ranks for EPDs for the remaining selection criteria, rank your interest in the bulls or females according to their EPDs, considering all traits in the selection criteria at one time. Some traits may have antagonistic relationships (such as calving ease vs. growth or maintenance energy vs. milk production), so getting a feel for which bulls or females have the optimal EPDs for all traits of interest is a vital step in choosing animals on which to place bids.

At the Sale 8. Visually evaluate the animal. Evaluate the bulls or females that you previously

ranked to assess their fitness for traits in which EPDs are not offered. Examples of traits commonly evaluated using only the animal’s phenotype include conformation, soundness, and fluidity of movement, and docility, among others. Eliminate any animals not sound and those that may have limitations in your environment due to physical characteristics. Also eliminate animals that possess a disposition that is unacceptable to you. You should now have a final ranking of the bulls or females.

9. Look at Sale Order and Supplemental Sheets. Make sure to pick up supplemental information sheets

and the sale order. Supplemental sheets will contain any corrections to the catalog and may include updated weights, DNA testing information, pregnancy data, or ultrasound data not available at the time the catalog was printed. This may eliminate additional animals from your list. Additionally, find the sale order for the bulls and compare it to your final ranking. With luck, the sale order of the bulls you’re interested in will be consistent with your ranking.

10. Devise a strategy for bidding. Strategize your purchasing decision given your rank-

ings and the sale order. Knowing the average from the previous year’s sale and/or the range of prices for those bulls or females may be useful in helping define your budget. If you have a relationship established with the breeder, you may be able to obtain additional advice on which animals are in great demand and may be out of your price range, and that information can help you decide whether to wait for a more highly ranked bull later in the sale order, or to go ahead and bid on a lower ranked bull earlier in the sale order.

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Oklahoma Cooperative Extension Fact Sheets are also available on our website at:

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Oklahoma Cooperative Extension Service

Megan Rolf Assistant Professor

In recent years an abundance of genetic defects in a variety of breeds have resulted in substantial associated economic losses. In this fact sheet, we will discuss how these defects are inherited, how to determine the probability of producing an affected calf, and strategies to decrease issues related to genetic defects in your herd.

Inheritance The bovine genome is made up of 29 pairs of autosomal chromosomes plus the sex chromosomes. Genetic defects are a result of alleles that cause a lethal condition or that severely handicap the performance of an individual. Simply speaking, at any location in the genome where there is a mutation, there are two alleles, which can be thought of as alternate forms of a gene. One allele comes from the sire and the other from the dam. There are many mutations within the genome which cause no known effects. However, the ones which are of interest are either ones which cause small effects on phenotype (The animals’ performance or how it looks), typically for performance traits, and those which cause large detrimental effects on phenotype or are lethal. Most genetic defects in beef cattle are a result of recessive autosomal mutations. The term recessive autosomal reflects the mode of inheritance for these defects meaning the muta-tion is on one of the 29 autosomal chromosomes (not a sex chromosome), and it is not expressed as a phenotype unless the animal receives two copies of the damaged allele (one on each of the two chromosomes inherited from its parents). The inheritance of these genetic defects works exactly like the inheritance of horns or red coat color, which are also autosomal recessive conditions and which require two cop-ies of the red (or horned) allele before a difference is seen in phenotype. Because these traits are recessive, possessing only one copy of each of these alleles (a defect, red color, or horns) is not enough to change phenotype, because it is masked by a dominant allele (normal condition, black color, or polled). These animals are often called carriers, because they carry a recessive condition, but do not express it. In any mammalian genome (the size of most mammalian genomes is three billion base pairs), it is almost assured that there will be multiple recessive lethal genetic defects pres-ent within the DNA sequence. However, because they are recessive, there must be two copies in the genome (one from each parent) in order to see affected progeny. In practice, the pairing of two disease alleles rarely occurs when animals are not inbred, because each animal likely carries mutations that cause different diseases. One of the best strategies to avoid incidence of genetic defects is to avoid mating animals to

Using Genomics Part II: Risk Management of Genetic

Defects

their relatives, or to employ a planned crossbreeding system (but keeping carrier status in mind when mating animals that have common breed composition).

Determination of Risk When the mode of inheritance is known, we can calculate the probability of producing an affected calf by knowing the carrier status of the parents. Because the normal allele is dominant, there is no way to visually determine which animals are carriers and which are not. The only way to make that determination is through genetic testing or through known parentage of an affected calf. If the animal tests as normal for a particular genetic defect, it has two normal alleles (represented by NN) and if the animal is tested and determined a carrier, it has one normal allele and one disease allele (represented by Nn). If an animal has ever produced an affected progeny (has the defect shown by phenotype, represented by nn), they can automatically be determined a carrier (Nn) and do not need to undergo genetic testing. If an inherited disease/defect is lethal, all adult animals are either normal or carriers (NN or Nn). They cannot have two copies of the disease allele (nn) and live. When the carrier status of the parents is known, we can calculate the probability of producing normal, carrier, or affected progeny using what is called a Punnet square. It is simply a square with four quadrants and works like a multiplication table. The alleles for each possible parental gamete (sperm and egg) are placed around the outside and the letters are matched on the interior squares and the percentages are multiplied together to determine the probabilities of each status in the progeny. To illustrate this point, consider the following examples:

Example 1. Punnet square for the mating of two normal (NN) animals. Male

Potential N N Gametes 50% 50%

N NN NN Female 50% 25% 25%

N NN NN 50% 25% 25%

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In the example shown on page 1, the two parents tested as normal, and do not carry any disease alleles. Because each gamete will contain one of the two parental gametes, each one will be seen approximately 50 percent of the time. Both parents are normal, so we have N gametes 100 percent of the time and all progeny (inside the bolded square) will have all normal alleles. This result illustrates why animals can be declared “clean” through pedigree. If the sire and dam have both been tested and determined carrier-free, any progeny of the mating will be free of disease alleles and do not need to undergo genetic testing.

Example 2. Punnet square for the mating of one normal (NN) and one carrier animal (Nn).

Male

Potential N n Gametes 50% 50%

N NN Nn Female 50% 25% 25%

N NN Nn 50% 25% 25%

In example 2, we have a mating of a carrier bull to a normal female. The female’s gametes will assort the same as in example 1, and she will always contribute N (normal) alleles to her progeny. The sire, however, can contribute ei-ther a normal (N) or disease (n) allele to his progeny. Each allele will occur in approximately 50 percent of his gametes, meaning ½ will be normal and ½ will contain the disease al-lele. When we match the possible gamete combinations (seen inside the bolded square), we can see that ½ of the calves (50 percent) will have two normal alleles (left side of the bolded box) while the other 50 percent of calves will be carriers (Nn; on the right, in light gray). In this scenario, we never see any affected calves, but they do have the potential to transmit the disease alleles to progeny in the next generation.

Example 3. Punnet square for the mating of two carrier animals (Nn).

Male

Potential N n Gametes 50% 50%

N NN Nn Female 50% 25% 25%

n Nn nn 50% 25% 25%

The only time affected calves are generated is when two carrier animals are mated together, such as illustrated in example 3. Each sire and dam produces 50 percent gametes with normal alleles and 50 percent with disease alleles. When combined together in the progeny (bolded black box) all three

genotypic classes can be present. This can be interpreted in terms of each progeny or in terms of a group of progeny produced from a group of carrier sires and dams. In the for-mer, each progeny from the mating would have a 25 percent chance of having two normal alleles, a 50 percent chance of being a carrier (light gray), and a 25 percent chance of being affected (dark gray). In a group scenario (i.e. a large number of full-sib flush mates), we would expect 25 percent of progeny to have two normal alleles, 50 percent to be carriers and 25 percent to be affected. Knowing the carrier status of the herd through genetic testing makes effective risk management possible.

Strategies to Manage Risk of Genetic Defects Whether or not there is a genetic test for the defect you are interested in managing will dictate how the incidence of genetic defects can be managed. If there is a test available for the genetic defect, it is advantageous to test those ani-mals which have never had an affected calf, placing special emphasis on testing individuals which have carrier animals in their pedigrees. There is no need to test any animal that has parented an affected progeny since they are known carriers or is out of two animals that are tested “clean.” If an animal is genetically superior in many other ways, but is a carrier of a genetic defect, they do not need to be culled immediately. As you saw from the Punnet square examples above, as long as a carrier is always mated to an animal that has two normal alleles (homozygous normal), they will never have affected progeny. However, those progeny will then need to be tested to determine if they are carriers. It is a good risk management practice to test any animals that will be retained, such as replacement females. As a general rule, animals scheduled for culling do not need to be tested. If you have seedstock, be cognizant of any breed registry requirements relevant to an animal’s carrier status. Some breed associations do not allow carrier animals to be registered, and most will require testing to determine carrier status if there are carriers in the animal’s pedigree, provided that a genetic test exists. Often progeny of animals that are carriers can be registered if the genetic test shows the animal itself is not a carrier. It is much more effective to know these requirements before making decisions regarding replacement females or culling, rather than suffering the consequences after the fact. Breed associations do a very good job of identifying and clearly displaying the status of carrier animals on the breed association webpages (Figure 1). Commercial cattlemen may find it easier to manage the genetic defect, rather than indiscriminately cull animals. For example, if a known normal (NN) bull is purchased, the carrier status of females may not matter because you will have 100 percent normal calves with an autosomal recessive defect. Alternatively, if you are using a bull in one breed on cows of another breed in a crossbreeding program, the likelihood of encountering the same defect in two different breeds is extremely small. Because of this, crossbreeding can be an effective risk management strategy for genetic defects. How-ever, it should be noted that care must be taken when keeping replacement females and utilizing bulls of the same breed in subsequent years so that no affected calves are produced.

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Testing Procedure and Availability If you would like to order DNA tests for genetic defects, there are two main providers for beef cattle. You can obtain more information on testing procedures, pricing, and a list of available tests on their websites. If you are a seedstock producer, you may need to submit the sample to the breed association rather than directly to a testing company, so please contact your breed association to find out more information on their guidelines for genetic testing.

Igenity

Testing Services: http://www.igenity.com/beef/profile/Abnormalities.aspx

Contact Information: http://www.igenity.com/ContactUs.aspx

Figure 1. Example of a carrier animal and its pedigree clearly identified by the American Angus Association. Carrier status on an animal that has undergone genetic testing can be found on the corresponding breed association web page for any animal. (Figure courtesy of Brian Freking)

Zoetis Animal Genetics

Testing Services: https://online.zoetis.com/US/EN/Pages/Animal%20Genetics.aspx

Contact Information: https://online.zoetis.com/US/EN/Products/Pages/AllAboutP-fizerAnimalGenetics.aspx

Knowing how genetic defects are inherited can assist in making good management decisions both to preserve genetic progress and reduce or eliminate economic losses associated with genetic defects. In addition, awareness of genetic defect testing and how to calculate the risk of producing affected progeny will help to analyze risk and manage the incidence of genetic defects and their associated economic losses in the herd.

Carrier status for animals

in the pedigree

Carrier status for the animal

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