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The Use of Progesterone in the Synchronization of the Estrual Periods in a Group of Ewes and the Effect on their Subsequent Lambing Records¹

University of Wisconsin

Abstract

The effects of 10 mg. progesterone daily for 14 days on synchronization of estrual periods of ewes during the breeding season and on subsequent lambing percentage was studied in a controlled experiment involving thirty-nine ewes. Seventy percent of the injected ewes came into heat on the third day after the end of treatment and the average time at which they were bred was 3.7 days after end of treatment, standard deviation 1.7 days. In the control group the average time of breeding was 9.2 days from the beginning of their breeding period, standard deviation 5.1 days.

The standard deviation of the lambing period was reduced in the progesterone treated group to 1.9 days as compared to 5.7 days in the control group.

No difference in the fertility of the two groups was demonstrated since the percentage of ewes lambing was 78.9 of the control group and 80.0 of the treated group, and the number of lambs born was 20 in the former group and 19 in the latter.

¹ Paper from the Department of Genetics and the Department of Animal Husbandry (Genetics No. 430).