عنوان مقاله [English]
نویسنده [English]چکیده [English]
Embryonic mortality is a common cause of economic loss in sheep. Insufficient luteal function and low concentration of maternal progesterone is one of the major reasons of this mortality. This study was conducted to investigate the effects of GnRH and hCG administration on day 5 after mating on reproductive performance in ewes. Total of 60 synchronized ewes were mated with fertile rams and equally were assigned to four groups. Ewes in GnRH, hCG and hCG+GnRH groups (n=15/group) received an i.m. injection of 25 μg GnRH analogue, 400 IU hCG and 25 μg GnRH analogue + 400 IU hCG on day 5 post-mating, respectively. The ewes in the control group (n=15) did not receive any treatment. Blood samples were collected on days 7, 12, 17 and 22 post-mating. Plasma P4 concentrations were higher at days 12 and 17 and 22 postmating in GnRH, hCG and hCG+GnRH treated ewes than those of control ewes (P < 0.05). There was no difference in lambing rate and litter size of ewes as well as in birth weight of lambs in different groups. Weaning weight of single lambs in hCG+GnRH group (34.08 ± 0.12 Kg) was greater than that of other groups. In conclusion, the results of this study demonstrated the efficiency of GnRH and hCG administration on day 5 after breeding to increase the maternal P4 concentrations. However, there was no significant effect of such hormonal treatments on reproductive efficiency of Afshari ewes.