Follicle Growth and Control of Ovulation in the Ewe Following Treatment with 6-Methyl-17-Acetoxyprogesterone

Abstract

MAP given at levels of 40, 60, 75, or 200 mg. per head daily inhibited heat and ovulation in ewes during treatment and for at least 48 hr. afterward. Follicles did grow during the normal follicular stage of the estrous cycle, while ewes were being treated with 40 or 60 mg. of MAP daily. Heat usually occurred about 54 to 72 hr. after last MAP treatment. Ovulation time was not well correlated with the time of last MAP treatment nor with the time of onset of heat. Ovulation occurred about 25 hr. after intramuscular injection of 500 I.U. of HCG. Control of the time of ovulation by this means may be useful as a tool in reproductive physiology research and in practical sheep husbandry.