Synchronization of estrus and ovulation in ewes by means of a progestin treatment combined with either PMSG or PGF2.ALPHA..

Abstract

Effects of an administration of 750IU pregnant mare serum gonadotropin (PMSG: group I, 13 ewes) and 15 mg prostaglandin F2α (PGF2α: group II, 15 ewes) after a progestin treatment with methyl-acetoxyprogesterone (MAP) through vaginal sponge for 9 days on synchronization of estrus and ovulation, and the subsequent fertility were compared with that of cycling ewes during the breeding season. The changes in plasma steroids (estradiol-17β: E2 and progesterone: P) concentrations were also estimated. All treated ewes showed estrus within 5 days after the treatment and all of the 4 laparotomized ewes in each group were ovulated when examined 8 days after the treatment. The number of ovulations in group I appeared to be greater than that in group II (3.25±0.63 and 1.75±0.25 per ewe), although the difference was not significant. Conception rates were expressed non-return (16-21 days), pregnancy (50-70 days) diagnosed by a Doppler method, lambing rate and number of lambs born per ewe. There was no significant difference in fertility between the two groups probably due to a small number of ewes used. The changing pattern of plasma concentrations of E2 and P was similar between the two groups. The MAP sponge treat-ment combined with PMSG appears to be more effective than MAP sponge combined with PGF2α treatment for synchronization of estrus and ovulation in cycling ewes.