Occurrence of Post-Partum Estrus in Fall-Lambing Ewes

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Abstract
Approximately 9% of 240 grade Rambouillet ewes lambing in the period October 10, 1957, to January 30, 1958, exhibited post-partum estrus between 15 and 27 hours after parturition. Similarly, 1% of 274 grade Rambouillet ewes lambing between June 24, 1958, and January 28, 1959, had a post-partum estrus. No post-partum estrus occurred in ewes lambing before October 10 the second lambing year. Of 20 Rambouillet ewes that had a post-partum estrus the first year and lambed again the second year, only two had a post-partum heat the second year. The average length of the post-partum estrual period was 2.4 checks the first year and 2.0 the second year. The checks were made at approximately 12-hour intervals. Ewes having a post-partum estrus in the 1957 lambing year returned to a cyclic pattern of estrual behavior an average of 61 days after lambing, compared with 73 days for ewes not having a post-partum estrus. Corresponding figures for the 1958 lambing year were 62.8 days and 86.1 days. The ovaries of ewes slaughtered 1 day after the end of post-partum heat were small and inactive and practically devoid of follicular growth. The injection of 50 U.S.P. units of purified oxytocin preparation was without effect in producing or inhibiting post-partum estrus. Copyright © 1964. American Society of Animal Science . Copyright 1964 by American Society of Animal Science

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