Control of Estrus and Ovulation in Gilts by Orally Effective Progestational Compounds

Abstract

Estrous activity was not inhibited in 3 of 11 gilts receiving from 0.9 to 2.0 mg. of 17-alpha-acetoxyprogesterone per lb. body weight per day by oral administration. The control of estrus and ovulation has been obtained in mature gilts by twice-a-day feeding of 6-methyl-17-acetoxyprogesterone. Twice-a-day feeding of 0.8 to 1.6 mg. of 6-methyl-17-acetoxyprogesterone per lb. body weight per day resulted in complete inhibition of estrus and follicular growth during the treatment period. Estrus occurred, on the average, 4.4 days from the end of treatment, and the start of estrus was synchronized within a 36-hour period. Autopsy following the controlled estrus demonstrated that ovulation had occurred. Immature gilts receiving 1.6 mg. of 6-methyl-17-acetoxyprogesterone for 10 days followed by the subcutaneous injection of 1000 I.U. of equine gonadotropin came into estrus within a 12-hour period 4 days following the gonadotropin injection. Autopsy 24 to 36 hours after the start of the induced estrus indicated that the follicular development and subsequent ovulation were normal. Orally active progestational compounds, administered as feed additives to the normal ration, could offer a means of controlling the time of breeding in swine applicable at the practical level. Copyright © . .