A comparison between the Effects of supplementary feeding and eCG on fertility and multiple ovulation rate in Zel ewes during summer

BACKGROUND: Considering the difference between the rate of multiple ovulation and ovarian activities of different breeds of ewes in different regions, especially out of seasonal breeding condition, finding efficient and effective protocols to induce multiple ovulation out of seasonal breeding would be much appreciated. OBJECTIVES: This study was conducted to determine fertility and multiple ovulation rates during summer and investigate the effect of supplementary feeding, and eCG injection prior to mating in the reproductive performance of Zel ewes. METHODES: At the beginning of summer, 135 ewes in Savadkooh region (north of Iran) were randomly selected and divided into six groups. The estrus cycles of ewes, except in control groups, were synchronized using a vaginal sponge for 14 days. In groups 1 (n=22) and 2 (n=22) ewes were fed with supplementary feeding for 21 and 8 days, respectively, prior to mating. In Group 3 (n=26) ewes were fed with the same ration as Group 2 and were injected (IM) with 400 IU eCG at the time of sponge withdrawal. Ewes in Group 4 (n=23) just grazed on the pasture and injected with eCG as Group 3. In Group 5 (n=20) the estrus of ewes was synchronized as other groups, but they were not received any other treatment. Ewes in Group 6 (n=22, Control) received no treatment, and as the same Group 1 and 2 were mated with fertile rams for eight weeks. Experimental ewes were mated with fertile rams (1:8) 48 hrs after sponge removal for 96 hrs. RESULTS: The findings showed that the fertility in group 3 was significantly more than group 2 and 5, but there was no significant difference between the others (p>0.05). The prolificacy and fecundity were significantly higher in groups treated with eCG than the others (p<0.01), however there was no significant difference between groups 3 (with flashing) and 4 (without flashing). CONCLUSIONS: It could be concluded that vaginal sponge and eCG treatment may improve the multiple lambing and reproductive performance of Zel ewes during summer, and supplementary feeding prior to mating, as described in this experiment, cannot make any significant improvement in multiple lambing.