Ovarian Activity and Reproductive Performance of Mature Ossimi Ewes as Affected by Presence of Ram

Abstract

Two experiments were conducted in this study to assess the role of ram effect prior to mating on ovarian follicular dynamics and reproductive performance of Ossimi ewes. In Expt. 1, fourteen Ossimi ewes 3-6 years old were used. The first group (n=7), ewes were exposed with two trained teaser rams (REG), whilst, the second group (n=7) remaining ewes were isolated of rams (CG). The number and size of all follicles ≥2 mm and corpus luteum were monitored by ultrasonography. Expt. 2, including two mating season, 70 Ossimi ewes (3-6 years old) were selected from 115 ewes in each mating season, multiparous, non-lactating and clinically healthy. The first mating season (n=70), ewes were kept in the presence with teaser rams (REG) during the estrus detection and mating for two consecutive estrous cycles (45 d). The second mating season (n=70), ewes were remaining isolated of rams (CG) except at the time for detection of estrus. Ewes were mated after detection of estrus. While, ewes return to estrus, were mated again. At lambing, birth dates and the lambs born number per each ewe were recorded. All ewes isolated of males for three months before the beginning of the experiments. There were significant (P < 0.01) increases in the small (2-2.9 mm) and medium (3-5 mm) follicles number on ovaries of ewes in REG compared to CG. Moreover, the size of maximum ovulatory follicles and subdominant follicles (next largest follicle) were larger (P <0.001) in ewes of REG compared with those of CG. In addition, the ovulation rate mean was higher (P =0.05) in the REG than that of the CG (Expt. 1). The lambing rate was higher (P <0.01) in the first mating season (REG) compared to the ewes in the second mating season (CG). At the same time, the mean number of fecundity and litter size were higher (P <0.01) in the REG compared to the CG. Moreover, twining lambing rate was higher (P <0.01) in the REG. by contrary, the percentage of single lambing was lower (P <0.01) in the first mating season (REG). The percentage of ewes lambing at first service was higher in the REG than in CG but the difference was insignificant (Expt. 2). In conclusion, these results show that, ram introduction prior to mating season increased the ovarian activity and reproductive performance after period of isolation of Ossimi ewes.