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Influences of using bovine somatotropin on estimates of genetic parameters and genetic evaluation of dairy cows
Records of 142,937 of registered and grade Holstein cows for yield traits and somatic cell scores (SCS) some with and some without bovine somatotropin (bST) treatment provided by the Dairy Records Processing Center at Raleigh, NC. were used to assess potential impact of bST on estimation of genetic parameters and on genetic evaluations when not all cows receive bST treatment. To investigate the relationship between genotype and response to bST, for yield traits and SCS, REML with multiple trait animal models, which considered yields with bST and without bST as different traits, were used. Animal models with and without adjustment for bST were also used for prediction of breeding values, and to study the effects of bST on genetic response to selection and on ranking of superior cows. Genetic parameters for first lactation yields were estimated with different two-trait animal models. ^ Significant effects of bST treatment on yield traits were found, with responses to bST greater for registered than for grade cows. Management practices for herds with grade cows could be the main reason for this difference. Estimates of heritability for both registered and grade cows with bST treatment were 0.22, 0.19, 0.18 and 0.23 and repeatability estimates were 0.44, 0.45, 0.43, and 0.41 for milk, fat and protein yields and SCS, respectively. Estimates of heritability for cows without bST treatment were 0.17, 0.19, 0.18, and 0.21, and repeatability estimates were 0.39, 0.40, 0.39 and 0.36 for milk, fat, and protein yields and SCS, respectively. Strong favorable genetic and permanent environmental correlations were found between the traits with and without bST treatment. Correlations among breeding values for all traits predicted by different models were greater than 0.968. A large proportion of top 2% of cows were chosen when ranked by genetic evaluations from all models. The decline in genetic progress for yield traits due to ignoring the use of bST would be negligible. Estimation of genetic parameters of first lactation yields obtained using models that adjust for or do not adjust for bST treatment were similar. ^
Biology, Genetics|Biology, Animal Physiology
Al-Jumaah, Riyadh S, "Influences of using bovine somatotropin on estimates of genetic parameters and genetic evaluation of dairy cows" (2001). ETD collection for University of Nebraska - Lincoln. AAI3034358.