Inclusion of Semen Price of the Sire in an Animal Model to Account for Preferential Treatment

¹ Department of Animal and Poultry Science, University of Guelph, Guelph, ON, Canada N1G 2W1

Histories of semen price for AI bulls used from 1970 to 1991 were collected and merged with first lactation milk and fat records of Ontario Holstein cows calving from 1970 through 1990. Data were analyzed with two animal models, both of which included herd-year-season and animal additive genetic effects. The second model included a fixed effect for semen price group. Cows that did not have a semen price for their sire were assigned to a separate group. Both models were used for milk and fat yields, and the second model was used separately for the semen price group of the sire at the time of daughter's conception, birth, and first calving. Hypothesis testing of group differences for semen price (excluding the group without a price match) resulted in significant effects of price group at first calving for milk and fat yields. The changes in estimated breeding values for cows and sires were summarized for cows by year of calving and for sires by Canadian versus US. Very few animals were affected by the inclusion of semen price groups in the model. Inclusion of effects of semen price group in an animal model did not significantly improve the accuracy of animal evaluations.

Key Words: preferential treatment • semen price • animal models

Submitted on May 10, 1993
Accepted on September 27, 1993

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