Effect of Superovulatory Regimens on Ovarian Response and Embryo Production in Fine Wool Sheep in Tropics

Abstract

Fine wool sheep (n=18) maintained in a tropical environment were allocated to three treatment groups. Estrus was induced with two injections of PGF2a (10 mg, im) at 10 days interval. Superovulation treatment started 2 days prior to the second injection of PGF2a. Each ewe was treated with a total dose of 25 units FSH (Super-OV) i.m. every 12 h over 3 days; Group 2 were also injected i.m. with 200 IU PMSG at the first injection of FSH; Group 3 was treated as in Group 2 and also with GnRH (4 μg Buserelin) at the onset of estrus. The ewes in estrus were mated with a fertile ram. Ovarian examination and recovery of embryo and ova were performed at laparoscopy and laparotomy on day 3 or 4 after mating. Data for onset of estrus, duration of estrus, number of corpora lutea (CL), number of unnovulated large follicle (LF), embryo recovery rate, embryo quality and fertilization recorded for the 3 groups. Ewes in the Group 1 set in estrus later (p<0.05; 50.0±7.29 h) than the ewes in Group 2 (24.5±3.58) and 3 (32.5±3.58 h). The duration of estrus, ovarian size and ovarian response (number of CL and LF) did not differ significantly (p>0.05) among the 3 groups. The proportion of ewes with a superovulatory response (≥2 CL) was the lowest (50%) in Group 1 treated with FSH alone but ova/embryo recovery (100%) and fertilization (100%) was significantly (p<0.05) higher than Group 2 (58.3 and 85.7%, respectively) and Group 3 (48.6 and 50%, respectively). It is concluded that in tropical fine wool sheep, there is no difference in the 3 treatments for yield of good quality embryos but ovarian response and ovulation rate increased on additional use of PMSG and GnRH respectively to FSH alone.