The Relationship of the Interval between Inseminations to Bovine Fertility3

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Abstract
Data showing the interval between two consecutive artificial inseminations (4885 cases) to cows were collected along with the fertility data for each interval as determined by 180 day non-returns to service. The distribution of these intervals showed definite peaks in numbers at 21 and 42 days. Based on the total recorded intervals up to and including those of 72 days length, 56 percent fell in the 18 to 25 day class, while 82 percent fell in this class when the totals for the first 35 days only were considered. The fertility levels based on non-returns to service after cows were inseminated 2–17, 18–25, 36–50, and 51–72 days after the previous insemination were 34, 49, 45, 50, and 54 percent; respectively. Only the fertility of those cows that returned for insemination at intervals of 2 to 17 days differed significantly from the mean fertility level. An increase of approximately 20 percent in the number of cows settled at any one estrus is indicated for a practice of breeding all cows regardless of the interval at which they return from a previous insemination as compared to a policy of breeding only those cows returning between 18 and 25 days after the previous service. Copyright © . .

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