Ovarian response and embryo recovery to different superovulatory regimens in Rambouillet ewes under semi-arid conditions

Abstract

Twenty four adult Rambouillet sheep were allocated in equal number to three groups and treated for superovulation using 800 IU pregnant mare serum gonadotrophin (PMSG) and GnRH (4 μg) (Group 1); PMSG (400 IU) in conjunction with FSH (8 ml; Ovagen) (Group 2) and FSH-P (18 mg) (Group 3). Estrous in all the ewes was synchronized by means of two 10 mg injections of prostaglandin F2α (PG), administrated at a 10 day interval. Superovulation treatment started 48 h prior to last PG injection. When in estrous, the ewes were naturally mated with Rambouillet rams. Ovarian examination and embryo/ova recovery were performed at laparotomy on either day 3 or 4 after mating. All the ewes exhibited estrous at ≤72 h after the last PG injection. The interval from the last PG injection to the onset of estrous was significantly ( P<0.05) shorter in the ewes treated with the FSH and PMSG combination (Group 2) compared to Group 1 and 3, respectively. No significant differences with respect to ovarian dimensions (length and breadth) and ovulation rate was recorded between the three treatments. The highest ovulation rate was recorded in Group 2 (6.6±1.99), followed by Group 3 (5.9±1.99) and Group 1 (3.6±2.29). However, total ovarian response (CL+LF), proportion of ewes with a superovulatory response (>2 CL) and ova/embryo recovery rate were lower ( P<0.05) in Group 1 ewes compared to the other groups. The proportion of fertilized ova was lowest (34.5%) in the ewes treated with the FSH and PMSG combination, compared to that in Group 1 (100%) and Group 3 (86.2%), respectively. It is concluded that Rambouillet sheep in semi-arid tropics can be superovulated for embryo production with FSH-P or with a combination of PMSG and FSH. FSH-P showed superiority over PMSG+GnRH and FSH+PMSG treatments in terms of total embryo production.