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

Department of Animal Husbandry, Cornell University, Ithaca, New York

ABSTRACT

1. Since the beginning of the New York Artificial Breeders' Cooperative in June, 1940, until June 30, 1944, a total of 12,621 complete, recorded services to registered Holstein-Friesian cows, involving 41 bulls, have accumulated. This number is 22.4 per cent of all matings to Holstein-Friesian bulls.
   
2. The average number of services required per conception when based on all females, infertile cows included, was 2.07, or a breeding efficiency of 48.2 per cent.
   
3. The influence of the age of the cow on breeding efficiency reveals a steady increase in the conception rate up to four years of age. Between the ages of five to seven years, inclusive, cows maintain a uniformly high breeding efficiency, which gradually declines with advancing age.
   
4. Although the full effect of the age of the sire could not be obtained with a group of bulls selected for fertility, young bulls between the ages of one to three years, inclusive, have shown the highest breeding efficiency of all age groups. Within this group the peak in conception rates was found for the two-year-old bulls.
   

^* The material contained in this report is from a thesis presented by T. Tanabe to the Graduate School of Cornell University, October, 1945, in partial fulfillment of the requirements for the degree of Master of Science in Agriculture.

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