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Hormonal control of the estrous cycle of the ewe during the breeding and non-breeding period

University of British Columbia

During normal breeding, the oral administration of 6-α-methyl-17-α-acetoxyprogesterone (MAP) or 6-chloro-Δ⁶-dehydro-17-acetoxyprogesterone (CAP) for 10 days successfully replaced Progesterone and Reposital Progesterone injections as treatments for inducing and synchronizing of estrus in adult ewes. During non-breeding, the oral administration of HAP or CAP over a period of 17 and 14 days respectively, successfully induced and synchronized estrus in dry and lactating ewes. CAP was found to be more potent in its progestational activity as compared to MAP. The supplementary treatment of Pregnant Mare Serum (P.M.S.) did not result in a significant increase of lambing percentage during the breeding period. The high dose of P.M.S. (1500 vs 1000 I.U.) did not appear to have any facilitating effect with regard to occurrence of induced estrus and increased lamb crop percentage during the anestrus period. Additional treatment with estradiol-17-β did not facilitate the occurrence of first induced estrus in treated ewes during the non-breeding period. The results indicate that conception and lambing rates are better from dry ewes than from lactating ewes during the anestrus period. The conception and lambing rates tend to improve when hormonal treatment is administered near the end of anestrus, as compared to hormonal treatment in the middle of the anestrus period.

Text

2011-09-06

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http://hdl.handle.net/2429/37120

Animal Science

University of British Columbia

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