Bias in Genetic Evaluations by Records of Cows Treated with Bovine Somatotropin

¹ Department of Animal Science, University of Nebraska, Lincoln 68583-0908
² Roman L. Hruska U.S. Meat Animal Research Center, ARS, USDA, Lincoln, NE 68583-0908
³ Department of Animal and Dairy Science, University of Georgia, Athens 30602-2771

Records from Dairy Records Management Systems in Raleigh were used to estimate effects of bovine somatotropin (bST) treatment and to predict breeding values for milk production traits. The data comprised 5245 test-day records of bST-treated cows and 126,223 test-day records of untreated cows in first lactation for milk, fat, and protein yields. Fixed effects of bST treatment were estimated from test-day animal models with herd-test-date as another fixed factor. Percentage increases due to bST treatment ranged from 7 to 8%for test-day milk, fat, and protein yields. Random regression coefficients for additive genetic and permanent environmental effects were included in the model. To assess the potential for bias in genetic evaluations when some and not all cows are treated with bST, breeding values predicted by the test-day model with and without effects of bST treatment were compared for cows and sires. Correlations between breeding values predicted from models with and without effects of bST treatment were 0.99. However, relatively large bias was found for individual animals. This result suggests that bias in genetic evaluation caused by ignoring bST treatment may be significant.

Key Words: dairy cattle • milk yield • breeding values

Submitted on December 13, 1999
Accepted on May 22, 2000

This article has been cited by other articles:

				A. Al-Seaf, J. F. Keown, and L. D. Van Vleck Genetic Parameters for Yield Traits of Cows Treated or Not Treated with Bovine Somatotropin J Dairy Sci, January 1, 2007; 90(1): 501 - 506. [Abstract] [Full Text] [PDF]