The use of FSH and GnRH as alternative compounds to PMSG for springtime breeding of ewes

Abstract

During early springtime, ewes were treated with a single injection of PMSG (500 IU) administered at the time of progesterone sponge withdrawal (Group I) or four, twice daily injections of FSH (2 mg each) administered from twelve hours before, to 24 hours after sponge withdrawal (Group II). One hundred μg of GnRH was administered 36 hours after sponge withdrawal in Group II. The two groups were compared with respect to estrous display, conception rate and other reproductive parameters. There were no significant differences (p>.05) between the two treatment group in any of the reproductive parameters measured. The occurrence of estrus during the first 96 hours after synchronization was low ( X = 45% of all treated ewes). Conception of all treated ewes during this estrous period was also low ( X = 32% of all treated ewes). The potential use of FSH and GnRH in estrous synchronization regimes was discussed. Possible reasons for the poor estrous and conception rates in present experiment were also considered.