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Journal of Dairy Science Vol. 57 No. 2 251-257
© 1974 by American Dairy Science Association ®
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Genetic Gain When Sire Sampling and Proving Programs Vary in Different Artificial Insemination Population Sizes1

M. S. Hunt2, E. B. Burnside, M. G. Freeman and J. W. Wilton

Department of Animal and Poultry Science, University of Guelph, Guelph, Ontario, Canada

ABSTRACT

Annual genetic gain for milk yield was simulated for artificially inseminated populations of 15,000, 50,000, 115,000, 350,000, 700,000, and 1,500,000 dairy cows. Variation in numbers of sires of young bulls, percentages of cows milk recorded and bred to young sires, and numbers of progeny in the test group were examined. Genetic gain was enhanced in all populations when the number of sires of sons used annually decreased from eight to two. A large percentage of the cows should be milk recorded and bred to young bulls if reasonable rates of genetic gain are desired in the small population. Similar estimates of annual genetic gain (1.52 Breed Class Average/yr) occurred in populations of 15,000 cows when 60% were milk recorded and 40% of these bred to young bulls, and 115,000 cows when 20% were milk recorded and 20% of these were bred to young bulls. When population size is small (15,000 cows), genetic gain is maximized by sampling the maximum number of bulls with approximately 20 daughters per bull. Larger cow populations can be improved more rapidly by sampling smaller numbers of bulls with more accuracy. All studs in North America are sampling too few bulls annually to approach maximum rates of genetic gain.

FOOTNOTES

1 Based on the M.Sc. thesis of the senior author and financed in part by the Ontario Ministry of Agriculture and Food and the Ontario Ministry of University Affairs.

2 Present address: Holstein-Friesian Association of Canada, Brantford.






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Copyright © 1974 by the American Dairy Science Association ®.