The Influence of Age on Breeding Efficiency of Dairy Cattle in Artificial Insemination

Abstract

A study of 12,621 artificial inseminations of registered Holstein-Friesian cows with semen from 41 registered Holstein-Friesian bulls showed that: The overall breeding efficiency was 48.2% of successful inseminations. There was a steady increase with the age of the cow in conception rate up to 4 yrs., followed by a fairly uniform high level through 7 yrs. and a decline with greater age. The 2-yr.-old bulls were the most fertile of all age groups, though carefully selected older bulls show high levels of fertility. The low reproductive performance of heifers in natural service as compared to older cows apparently is not due to physical in-compatability of the mates, for similar results were obtained in this study.