Recent estimates of genetic trend in the U.S. Holstein population -for milk, fat, protein and type show annual increases of 1.4, 1.3, 1.2 and 0.3% of the mean, respectively. New genetic information on several secondary traits is starting to be used. Genetic trend in young bulls is increasing at a faster rate than the cow population indicating that the eguilibrium rate of genetic progress has not yet been reached. High use of a few sires of sons can cause important fluctuations in genetic merit of young bulls. The average U.S. Holstein breeder is utilizing quantitative genetic information to make culling, mating and breeding decisions. Utilization of improvements in reproductive efficiency such as artificial insemination (AI) and embryo transfer (ET) are being made in conjunction with increased use of information on predicted transmitting ability (PTA) for additive genetic merit of animals.

Thomas J Lawlor, T. H Short

Proceedings of the World Congress on Genetics Applied to Livestock Production, Volume XIV. Dairy cattle genetics and breeding, adaptation and conservation., , 179–182, 1990
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