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United States Department of Agriculture

Agricultural Research Service

Title: Impact of Bovine Somatotropin on Ranking for Genetic Value of Dairy Sires for Milk Yield Traits and Somatic Cell Score

Authors
item Al-Seaf, Ali - UNIV. OF NEBR.-LINCOLN
item Keown, Jeffrey - UNIV. OF NEBR.-LINCOLN
item Van Vleck, Lloyd

Submitted to: Genetics and Molecular Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: December 11, 2006
Publication Date: March 9, 2007
Citation: Al-Seaf, A., Keown, J.F., Van Vleck, L.D. 2007. Impact of bovine somatotropin on ranking for genetic value of dairy sires for milk yield traits and somatic cell score. Genetics and Molecular Research. 6(1):79-93.

Interpretive Summary: Records of Holstein cows from the Dairy Records Processing Center at Raleigh, NC were made available for this study. The data were used to examine how different models account for effect of bST treatment on genetic evaluation of sires for milk yield traits and somatic cell score (SCS). The data were edited to obtain three data sets. Data set 1 included 65,720 records for first lactations only. Data set 2 included 50,644 records for second lactations only. Data set 3 included 45,505 records for lactations three, four and five. Breeding values of sires were estimated with three different animal models. With Model 1, bST administration (given or not given) was ignored. With Model 2, bST administration was used as a fixed effect. With Model 3, administration of bST was used to define the contemporary group (herd- year- month of calving- bST). Correlations for EBV of about 1,300 sires with treated daughters between pairs of the three models were calculated for milk, fat, and protein yields and SCS for the three data sets. Correlations for EBV of sires between pairs of models for the yield traits ranged from 0.987 to 0.999 for the three data sets and from 0.971 to 0.999 for SCS. Correlations were highest between the most similar models (1 and 2) and lowest for the most dissimilar models (1 and 3) although all correlations were near unity. Overall data sets and for all traits the fractions of sires with bST treated progeny selected in common based on largest 10 to 25% of EBV were greatest for Models 1 and 2 and were smallest for Models 1 and 3. Fractions selected in common were 0.94 and usually greater for all pairs of models for all traits and data sets. This study demonstrated that statistical adjustment for bST treatment for this set of records resulted in a negligible effect on genetic evaluations of sires when some daughters are treated with bST. The results suggest that selection of groups of sires to produce the next generation of sires and cows would not be significantly affected by how effect of bST is modeled for prediction of breeding values for milk, fat, and protein yields and for somatic cell score.

Technical Abstract: Records of Holstein cows from the Dairy Records Processing Center at Raleigh, NC were made available for this study. The data were used to examine how different models account for effect of bST treatment on genetic evaluation of sires for milk yield traits and somatic cell score (SCS). The data were edited to obtain three data sets. Data set 1 included 65,720 records for first lactations only. Data set 2 included 50,644 records for second lactations only. Data set 3 included 45,505 records for lactations three, four and five. Breeding values of sires were estimated with three different animal models. With Model 1, bST administration (given or not given) was ignored. With Model 2, bST administration was used as a fixed effect. With Model 3, administration of bST was used to define the contemporary group (herd- year- month of calving- bST). Correlations for EBV of about 1,300 sires with treated daughters between pairs of the three models were calculated for milk, fat, and protein yields and SCS for the three data sets. Correlations for EBV of sires between pairs of models for the yield traits ranged from 0.987 to 0.999 for the three data sets and from 0.971 to 0.999 for SCS. Correlations were highest between the most similar models (1 and 2) and lowest for the most dissimilar models (1 and 3) although all correlations were near unity. Overall data sets and for all traits the fractions of sires with bST treated progeny selected in common based on largest 10 to 25% of EBV were greatest for Models 1 and 2 and were smallest for Models 1 and 3. Fractions selected in common were 0.94 and usually greater for all pairs of models for all traits and data sets. This study demonstrated that statistical adjustment for bST treatment for this set of records resulted in a negligible effect on genetic evaluations of sires when some daughters are treated with bST. The results suggest that selection of groups of sires to produce the next generation of sires and cows would not be significantly affected by how effect of bST is modeled for prediction of breeding values for milk, fat, and protein yields and for somatic cell score.

Last Modified: 9/2/2014
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