Factors Affecting Calving Interval in Dairy Herds

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Abstract
A total of 696 calving intervals on 370 cows from 4 breeds in the Oklahoma State University [USA] dairy herd was used to study breeding efficiency and various factors affecting calving interval within breed. Fertility of bulls differed within breeds. Analysis by fitting constants revealed that intervals from calving to 1st service and from 1st serive to conception and services per conception were major factors affecting calving intervals. Dependent on breed, combinations of unit changes in these variables would account for the greatest overall reductions in length of calving interval. Month of calving, month of conception, year of calving, age at calving, and peak milk had no significant effect on changing the average calving interval.