Relative Genetic Merit and Effectiveness of Selection of Young Sires for Artificial Insemination

¹ Department of Dairy Science, Virginia Polytechnic Institute and State University, Blacksburg 24061-0315

Data were from 1913 proven AI Holstein sires that were available from January 1980 to July 1990 and 7942 young sires that were sampled during the same period. All young sires in this study had progeny test results available. The number of young sires sampled during this period increased by 35.7 bulls/yr, and the number of proven bulls available decreased by 12.6 bulls/yr. Young sires ranked at the 57th percentile of proven bulls with mean percentile rank decreasing .9/yr based on their progeny test results for dollar value of milk, fat, and protein from the USDA evaluations of January 1994. Selection to remove the bottom 25, 50, and 75% of the young sires on the basis of their parent averages from January 1994 increased mean percentile rank to the 68th. 76th, and 84th, respectively. For bulls sampled from 1987 to 1990, selection on the first available parent average gave 70% of the response as selection on parent average from January 1994. The absence of top-ranking graduates and low overall percentage of graduates justified culling the bottom 10% of young sires at 3 yr. The increasing number of AI and non-AI bulls sampled per year has increased the genetic merit of proven sires relative to AI young sires. Results suggest benefits to more intensive selection of young sires by breeders and AI personnel.

Key Words: young sires • artificial insemination • genetic progress

Submitted on March 16, 1995
Accepted on June 12, 1995

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