Farmer, Jack

Gibb, Jim

Strohbehn, Daryl

Wagner, Wayne

English

Texas A&amp;M Repository

11- ~.A.'l'S'"L-2166Texas Agricultural Extension ServiceUnderstanding andUsing Sire SummariesSire selection is one of the most important decisionsmade by a cow-calf producer. If it is effective, sireselection will account for nearly 90 percent of thegenetic improvement in a herd. In herds thatproduce their own replacement females, 87% per-cent of the heifer's genetic makeup comes from thelast three bulls used in the pedigree.Sire selection is more accurate today than everbefore. Breed associations have developed com-puter programs that utilize performance records on acalf's relatives in addition to its own record incalculating estimated breeding values (EBVs). Traitsevaluated include, but may not be limited to, birth,weaning, and yearling weights, and maternal breed-ing value for daughters' calving ease and weaningweight. Using these estimated breeding values in aselection program has improved the accuracy ofidentifying superior and inferior animals within aproducer's herd.cattle producers are evaluated in these summaries.Most sires listed in the summary have been used inA.1. programs across several herds.The traits listed vary slightly among breed siresummaries. They all evaluate the ability of a sire totransmit growth rate to his progeny in the areas ofbirth, weaning, and yearling weights. Most breedsalso evaluate the performance of daughters of thesire. This includes an evaluation of daughter calvingease and/or the ability of daughters to wean heavycalves (referred to as Maternal Breeding Value forweaning weight).Sire evaluation in the beef industry has become asophisticated procedure developed through experi-ence, research, improved statistical procedures, andthe development of large, high speed computers.Fortunately, a beef producer only needs to know afew basic concepts to interpret and use the results.TerminologyExpected Progeny Difference (EPD)Sire summaries use the term Expected ProgenyDifference (EPD) to express genetic transmittingability of a sire. The EPD is reported as a plus orminus value in the unit in which the trait is measured,such as pounds for birth weight. An example of theAngus Sire Summary, which is similar to those ofother breeds, is shown in table 1. An EPD foryearling weight of + 70.0 lb. indicates that progenyof this bull should average 70.0 lb. more at 365 daysof age than progeny of an average bull of the breed.On the other hand, a bull with an EPD of - 2.7 lb. forweaning weight would be expected to producecalves 2.7 lb. lighter at weaning weight than theaverage bull of that breed. Some breed associationsexpress EPDs as ratios. When ratios are used,The development of sire summaries has been a bigadvancement for the beef cattle industry. Siresummaries have given breeders an opportunity tomake more accurate selection decisions. With highcosts of production and competition from othermeats, cattle producers cannot tolerate mistakes intheir breeding programs. Therefore, the ability toutilize sire summaries is important to the individualproducer. Mistakes made on sire selection this yearwill show up in next year's calf crop. Three yearslater, the sire's genetic influence will become evidentagain as his daughters come into production.Most breed associations now produce and distributea sire summary. They are updated and printedannually. In most cases they are free to commercialcattle producers. Requests for sire summariesshould be made directly to the breed association'soffice. Traits that are economically important to mostPrepared by Wayne Wagner, West Virginia State University; Jim Gibb, American Polled Hereford Association; Jack Farmer, California cattlebreeder; and Daryl Strohbehn, Iowa State University. Reviewed by AI Smith, Virginia commercial producer; Darrell Wilkes, National Cattlemen'sAssociation; Roger McCraw, North Carolina State University; Kenneth W. Ellis, University of California; Dixon D. Hubbard, ExtensionService-USDA; Harvey Lemmon, Georgia angus breeder; Robert D. Scarth, beef breeding consultant; and A.L. Eller, Virginia PolytechnicInstitute and State University. Edited by Daryl Strohbehn and Gene Hettel, Iowa State University.Texas Agricultural Extension Service. Zerle L. Carpenter, Director. The Texas A&M University System. College Station, Texasconversion factors are given so the ratios can betranslated to EPO values. For example, the 1985Simmental Sire Summary indicates that a one unitchange in weaning weight ratio is equivalent to5.27 lb. Therefore, the EPO for weaning weight of abull with a weaning weight ratio of 102.5 is equal to+13.18 lb. (5.27 lb. x 2.5).EPOs are calculated from a sire's progeny data. Allbulls listed in the sire summary can be directlycompared using the EPO values. EPOs are anestimate of how a bull's progeny would be expectedto perform compared to any other bull listed in thesame summary.Studying table 1, one would expect progeny of bullB to weigh 39.1 lb. more at weaning than progeny ofan average Angus bull. One also would expectprogeny of bull C to weigh 53.8 lb. more at weaningthan progeny of an average Angus bull. Therefore,progeny of bull C should average 14.7 lb. (53.8 -39.1) heavier at weaning than progeny of bull B.Likewise, progeny of bull B should weigh an averageof 41.8 lb. more at weaning than progeny of bull A.AccuracyAn accuracy (ACC) figure is listed for each EPO asshown in table 1. Accuracy is a measure of howmuch the EPO value might change as additionalprogeny data become available. Sires with morecalves in several different herds will have higheraccuracy figures. A high accuracy figure in Angus,Limousin, Polled Hereford, and Hereford summariesindicates the EPO value will change very little asadditional progeny data are collected. The accuracyfigures shown in table 1 indicate that the weaningweight EPO of bull A could change considerablymore than the EPO for bull C. Low accuracy figuresin Simmental and Gelbvieh summaries indicategreater accuracy. Therefore, select bulls to usebased upon their EPO values and use the accuracyfigure to determine how much to use a bull.Maternal Breeding Value (MBV)Although bulls do not wean calves, their daughtersdo. Therefore, producers are interested in whether abull's daughters wean calves heavier or lighter thanaverage. Much of the influence a cow has on theweaning weight of her calf is a result of her ability tomilk. Maternal Breeding Value (MBV) describes howdaughters of a bull are expected to producecompared to other cows in a herd. An estimatedMBV can be calculated for an unproven bull usingproduction data on daughters of his sire andpaternal and maternal grandsires plus his dam'sprogeny. Once a bull's own daughters come intoproduction, the MBV is calculated using the recordsof his own daughters in addition to those of his sireand paternal and maternal grandsires.Estimates of MBVs come from pedigree analysis andnot sire evaluation. Therefore, MBVs are not directlycomparable between bulls as are the EPO values.Accuracy figures also are calculated differently. Anaccuracy figure of 0.95 for an EPO would indicate ahigh degree of accuracy, but a similar value for MBVis much less accurate.UtilizationBoth commercial and seedstock producers shouldfind sire summaries useful. A producer using A.1.can obtain semen from bulls that are superior in thetraits of interest. This eliminates much of theguesswork that existed in sire selection prior to theadvent of sire summaries. Thus, superior geneticsare readily available to cattle producers who canutilize A.1.Table 1. Example of sire summary data from the 1984 Angus sire summary.Evaluation reportBirth Weaningweight weightEPD ACC EPD ACCBull A -1.6 .81 -2.7 .79Bull B +2.4 .90 +39.1 .91Bull C +8.3 .97 +53.8 .97Yearling Maternalweight breeding valueEPD ACC EBV ACC DTS-3.2 .72 102 .80 13+70.0 .83 103 .76 11+80.4 .89 93 .66 5Advantage for progeny weaning weights:Bull B vs. bull A +41.8 lb.Bull C vs. bull A -t. 56.5 lb.Bull C vs. bull B + 14.7 lb.aACC =AccuracybOTS = Number of daughtersFigure 2 shows the effect of inappropriate sireselection on average breeding values in a herd.EPD in excess of + 75.0 lb. for yearling weight. Lessthan 2.5 percent would have an EPD in excess of+ 75.0 lb. Stacking pedigrees offers a tremendousopportunity to build genetically superior cattle whenbreeders use sire summary data correctly.Assume Great Expectation's individual performanceis superior and his dam also is superior inproduction. One would likely want to adjust theprojected EPD values upward. The extent of adjust-ment depends upon how much above average GreatExpectation's individual record and his dam's recordare compared to the herd average.How should producers use sire summaries forselecting young bulls? The projected EPD values foryearling weight calculated in the preceding para-graph for Great Expectation is an example of what iscalled a pedigree index. When nothing is knownabout the calf except the EPD value of his sire andmaternal grandsire, a pedigree index value can becalculated that becomes the best estimate of hisgenetic merit. Information on the production recordof the dam and Great Expectation's own perform-ance record also can be used to improve confidencein the evaluation of Great Expectation.Average CowYW EPD: 0.0 lb.Good Ole BullYW EPD: 50 lb.Average CowYW EPD: 0.0 lb.Good Ole BullYW EPD: 50 lb.Decent CowYW EPD: 251bBetter BullYW EPD: 65 lb.Decent CowYW EPD: 25 lb.Breeding DisasterYW EPD: -19.0 lb.Great ExpectationProj. YW EPD: 45 lb.Short ChangedProj. YW EPD: 3 lb.Figure 1Figure 2A pedigree for yearling weight has been stacked infigure 1. Great Expectation is the calf that willhopefully be produced. His maternal granddam wasAverage Cow. She was bred to Good Ole Bull whohas a yearling weight EPD of + 50.0 lb. This matingproduced Decent Cow. Based upon principles ofinheritance, the average calf from this mating wouldhave a yearling weight EPD of + 25.0 lb. [EPD ofDecent Cow = Y2 x (EPD of Good Ole Bull) +Y2 x (EPD of Average Cow)]. Now breeding DecentCow to Better Bull produces Great Expectation.Better Bull has a yearling weight EPD of + 65.0 lb.This kind of mating would, on the average, beexpected to produce calves that would have ayearling weight EPD of +45.0 lb. [45 lb. = Y2 x65 lb. (EPD of Better Bull) + Y2 x 25 lb. (estimatedEPD of Decent Cow)]. The EPD values of both thesire and dam have halved because they eachcontribute only one-half of their genetic makeup totheir offspring.Expanded UsageHow might a breeder use sire summary data toeffectively build a superior herd? It is done bystacking pedigrees or simply using bulls in succes-sion that excel in the same traits. In other words,breed the best to the best. For example, if you wantto improve the breeding value for yearling weight in aherd, breed bulls with high yearling weight EPDs todaughters of bulls with high yearling weight EPDs.Producers who rely on natural service can use siresummaries to select bulls that are sons and/orgrandsons of outstanding bulls in the summaries.Because a bull receives one-half of his geneticmakeup from his sire, sons of bulls with superiorEPDs are more likely to have superior breedingvalues themselves for the same traits. This isespecially true if their individual performance re-cords also are above average. Thus, summaries areparticularly useful to commercial producers.Summaries also can be used to identify herds thatexcel in genetic merit and vice-versa. A breeder whohas several superior bulls listed in the report is amore reliable source of bulls than either the breederwho has no bulls listed or the breeder who haspoorer than average bulls listed in the summary.If a large number of calves are produced from sucha mating, one would expect them to have anaverage yearling weight EPD of +45.0 lb. Thereactually is a variation of EPD values. Some calveswould have EPD values greater than + 45.0 lb. andsome would have EPD values less than + 45.0 lb.Based upon statistics it is known that nearly 68percent of the calves would have EPD values from+ 30.0 to + 60.0 lb. and 95 percent would have EPDvalues from + 15.0 to + 75.0 lb. for yearling weightand, likewise, less than 2.5 percent would have anFor example, take Decent Cow as in the previoussample and breed her to Breeding Disaster who hasa yearling weight EPD of -19.0 lb. One wouldexpect to produce progeny that would, on theaverage, have a yearling weight EPD of + 3.0 lb.Producers frequently make matings such as the onethat produced Decent Cow. However, because theirselection goals change, or another trait becomesmore important to them, they often use bulls onthese females that are below average in geneticmerit for growth rate. For example, Breeding Disastermight have been a bull selected because of histype. When sire selection is not effective, progresscan be slowed and even reversed.Selection for only one trait in a breeding programcan be a problem because of undesirable geneticcorrelations. Therefore, "stacking pedigrees," usingthe principles of single trait selection, could causesome unwanted problems. For example, there is apositive genetic correlation between yearling weightand birth weight. This means that selection foryearling weight also will increase birth weight if nonegative emphasis is placed on birth weight. Birthweight is highly related to calving difficulties. Aproducer, who is only interested in producing highEPD values for yearling weight, might also generatehigh EPD values for birth weight if he selects siresstrictly on their yearling weight EPD values asillustrated in figure 3.Hard PullYW EPD: 49 lb.BW EPD: 5.0 lb.Figure 3Higher PerformerYW EPD: 66 lb.BW EPD: 7.0 lb.Improved CowYW EPD: 32 lb.BW EPD: 3.0 lb.High PerformerYW EPD: 64 lb.BW EPD: 6.0 lb.Average CowYW EPD: 0.0 lb.BW EPD: 0.0 lb.The problem occurs because there is distribution ofEPD values around the expected average. In figure3, the projected EPD for birth weight is 5.0 lb., but68 percent of the calves from this mating would beexpected to have a birth weight EPD of +4.2 to+ 5.8 lb. and 95 percent would be expected to havea birth weight EPD of +3.4 to +6.6 lb. Not only hasa high EPD value been built up for yearling weight,but the same has been done for birth weight.Bulls with a combination of high EPDs for birth andyearling weights may be useful in terminal siremating systems. Females used on these bulls shouldbe mature cows to minimize calving difficulties. It isquestionable whether bulls with excessively highbirth weight EPDs should be used to sire replace-ment females. Calving problems have resulted inincreased death loss and calving intervals andlowered conception rates.To continue genetic improvement in a herd, eachnew sire or group of sires should be superior to thelast one used. In table 1, bull A would be a betterchoice to breed to heifers than bull B or bull Cbecause of his negative EPD value for birth weight.Bull B is probably the most useful bull in total meritbecause of his relatively high EPDs for weaning andyearling weights, his moderate EPD for birth weightand his above average MBV.SummaryAccurate sire selection is important to the cow-calfproducer. The effects of using a poor bull in a herdwill be evident for several years. Sire summariesprovide producers with accurate and reliable infor-mation on which to base selection decisions. Thesesummaries, which use EPD values, give producersthe opportunity to directly compare proven bulls witha high degree of accuracy. Bulls with low EPDvalues will sire some good calves and the best bullswill sire some poor calves. However, the performanceof a large group of c'a/ves by a sire should be similarto his EPD value. Sire summaries have taken muchof the guesswork out of breeding beef cattle.~W Reprinted by permission from the Beef Industry Federation.Educational programs conducted by the Texas Agricultural Extension Service serve people ofall ages regardless of socioeconomiclevel, race, color, sex, religion, handicap or national origin.Issued in furtherance of Cooperative Extension Work in Agriculture and Home Economics. Acts of Congress of May 8. 1914. asamended, and June 30.1914, in cooperation with the United States Department of Agriculture. Zerle L. Carpenter. Director, TexasAgricultural Extension Service. The Texas A&M University System.10M-7-85 AS-1

Understanding and Using Sire Summaries.

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Understanding and Using Sire Summaries.

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Understanding and Using Sire Summaries.

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