A linear model suitable for use by individual a rtificia l insemination (AI) units to obtain fe rtility ratings of AI bulls in service was developed. The model for 90 day non-return rate (90-d NRR) accounted for the service bull, age of service bull at the time’ of semen collection, technician and random herd-year-seasons. The program was applied to obtain fe r tility ratings of 228 Holstein AI bulls for 90-d NRR from a data set containing 205,046 firs t services on Holstein cows from one AI unit in Canada over of period of four years. All breedings were assumed to be random matings on different parity cows across herds. Differences in fe r tility rating solutions (FRS) for 90-d NRR of AI bulls ranged from -0.22 to +0.31. Prediction of fe rtility of young AI bulls and accurate rating of proven bulls is feasible with the computing fa cilities of AI studs and w ill be useful to the dairy industry.

K. Nadarajah, E. B Burnside, Larry R Schaeffer

Proceedings of the World Congress on Genetics Applied to Livestock Production, Volume XIV. Dairy cattle genetics and breeding, adaptation and conservation., , 175–178, 1990
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