|Van Vleck, Lloyd|
Submitted to: Journal of Animal Science Supplement
Publication Type: Abstract Only
Publication Acceptance Date: 7/24/1995
Publication Date: N/A
Technical Abstract: The objective was to compare estimates of genetic parameters resulting from different analytical models for birth weight (BWT, n=4155), 205-day weight (WWT, n=3884) and 365-day yearling weight (YWT, n=3476). Data consisted of records on Line 1 Hereford cattle selected for postweaning growth from 1934 to 1989 at ARS-USDA, Miles City, MT. Six models were compared: Model 1 included fixed effects of year, sex, age of dam, covariates for birth day, inbreeding coefficient of animal and inbreeding coefficient of the dam, and random additive genetic and residual effects. Model 2 was same as model 1 but ignored inbreeding coefficients. Model 3 was same as model 1 and also included additive maternal genetic with covariance, and permanent maternal environmental effects. Model 4 was the same as model 3 but ignored inbreed- ing coefficients. Model 5 was same as model 1 but with a random sire effect. Model 6 was the same as model 5 but ignored inbreeding coeffic- ients. Variance components were estimated from single and multiple trait analyses by derivative-free REML. There were no significant differences among models with and without inbreeding coefficients. Estimates of fractional variances and maternal-direct correlations from two trait analyses were nearly identical to estimates from single trait analyses for all models. Likelihood ratio tests showed significance (P<.01) between models 1 and 3 for WWT but not for BWT and YWT. Direct heritability esti- mates decreased by 11 to 49% when maternal and permanent environmental effects were included in the model. Likelihood ratio tests showed signifi- cance (P<.01) between models 1 and 5 for BWT, but not for WWT and YWT, and between models 3 and 5 for BWT and WWT but not for YWT.