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ARS Home » Plains Area » Clay Center, Nebraska » U.S. Meat Animal Research Center » Genetics and Animal Breeding » Research » Publications at this Location » Publication #152866
Title: EFFECTS OF SIRE MISIDENTIFICATION ON ESTIMATES OF GENETIC PARAMETERS FOR BIRTH AND WEANING WEIGHTS IN HEREFORD CATTLE

Author
item SENNEKE, S. - UNIV. OF NEBRASKA-LINCOLN
item Macneil, Michael
item Van Vleck, Lloyd

Submitted to: Journal of Animal Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/12/2004
Publication Date: 8/1/2004
Citation: Senneke, S.L., Macneil, M.D., Van Vleck, L.D. 2004. Effects of sire misidentification on estimates of genetic parameters for birth and weaning weights in Hereford cattle. Journal of Animal Science. 82:2307-2312.

Interpretive Summary: Misidentification of sires may be an important weakness in selection programs in the beef cattle industry. Other research has shown that sire misidentification causes the estimate of a negative direct-maternal genetic correlation to become positive, decreases estimates of both direct and maternal heritability, decreases genetic gain and biases evaluations of sires and estimates of breeding values. An appropriate model is needed to obtain unbiased estimates of genetic parameters needed for genetic evaluation. With the possibility of sire misidentification, one question is "Which model is best for estimating genetic parameters?" A common animal model used for genetic evaluation of beef cattle includes a fixed covariate of calendar birth date, fixed effects of year of birth, sex of calf, age of dam, and their interactions, random direct and maternal genetic effects and uncorrelated permanent environmental effect of the dam. A specific question is whether a model with or a model without sire by year interaction effects would more accurately estimate genetic parameters from data with some sire misidentification. The purpose of this study was to determine the effect of sire misidentification on estimates of genetic parameters for birth and weaning weights of beef cattle with those two models. The results from simulating random misidentification show that misidentification of sires can bias estimates of genetic parameters needed for national genetic evaluations. The bias will increase as misidentification increases. Including sire by year effects in the model did not compensate for effects of misidentification on estimates of direct and maternal heritability. Estimates of the direct genetic correlation between traits were not affected much by misidentification, but the estimate of the maternal genetic correlation between traits decreased by half with 50% misidentification. Misidentification will decrease genetic gain from selection due to bias in prediction of breeding values. Accurate identification of sires is needed to improve estimates of genetic parameters and predictions of genetic values.

Technical Abstract: A total of 4,155 birth weights and 3,884 weaning weights records of Line 1 Herefords collected at the Fort Keogh Livestock and Range Research Laboratory in Miles City, Montana between the years of 1935-1989 were available. To study the effect of misidentification, the sire identification of calf was randomly replaced by the identification of another sire based on the fraction of progeny each sire contributed to a yearly calf crop. Misidentification rates ranged from 5 to 50% with increments of 5%. For each rate of misidentification, 100 replicates were obtained and analyzed with single trait and two-trait analyses with a REML algorithm. Two different models were used. Both models contained year by sex combinations and ages of dam as fixed effects, calendar birth date as a fixed covariate, and random animal and maternal genetic effects and maternal permanent environment effects. Model 2 also included sire by year combinations as random effects. As the rate of misidentification increased, estimates of the direct-maternal genetic correlation increased for both traits, with both models, for all analyses. With single trait analyses, estimates of the proportion of variance due to sire by year interaction effects increased slightly for birth weight (near zero) and decreased slightly (0.015 to 0.004) for weaning weight as misidentification increased. With two-trait analyses, estimates of relative variance due to sire by year effects gradually decreased for weaning weight as misidentification increased. With the two-trait analyses, and with both models, as the level of sire misidentification increased, estimates of the genetic correlation between direct effects gradually increased, and estimates of the correlation between maternal effects gradually decreased. Estimates of the direct-maternal genetic correlation were more positive with Model 2 than Model 1 for all levels of misidentification. This study indicates that sire misidentification would severely bias estimates of genetic parameters and would reduce genetic gain from selection.