Institute of Animal Science, Department Sheep Breeding, BG - 2232 Kostinbrod, Bulgaria
METODIEV, N., 2015. Estrus synchronization of ewes by using “ram effect” and single treatment with synthetic analogue of PGF2α. Bulg. J. Agric. Sci., 21: 889–892
The aim of the present study was to induce synchronized estrus at ewes from Ile de France breed by using ram effect and single treatment with synthetic analog of PGF2α in various days after ram introduction. After contacting of 7th days with rams, 35 ewes, that didn’t show estrus, equal in age (from 2.5-to 3.5 years old), BCS (3.0-3.5), live weight of ewes (70-75 kg), clinically healthy and with normal last lambing, were assigned into 3 experimental groups: Group I – Treatment on day 7 (n = 12); Group II – Treatment on day 10 (n = 12); Group III – Control, without treatment (n = 11). On day 7th, 12 ewes randomly assigned (Group I) were treated with 125 μg cloprostenol. The rest of ewes were observed and those with manifested estrus were inseminated, as they were assigned to the control group. On day 10th another 12 ewes were treated with 125 μg cloprostenol and that was Group II. Ewes that remain untreated were assigned to control group, as they were observed for first manifested estrus. The ewes were inseminated naturally, by hand, as the first service was at first registered estrus and after that on 12 hour interval until the end of the estrus. The obtained results showed that scheme that was used at Group II had better effect of estrus synchronization (EES) than this of Group I (100% vs. 66.66%) , but the difference was not significant (*P > 0.05). The best fertility had Group I – 85.7%, and the lowest - Group II – 70.0%. The fecundity had the lowest value at Group I - 100%, as there was significant differences (*P < 0.05) between it and the values of Group II (157.14%) and Group III 166.66% (Table 1). The obtained results (100% ES, 70% pregnancy rate and 157.14 % fecundity) give us opportunity to recommend scheme, in which after 10 days of introducing the rams, ewes that didn’t show estrus have to be treated with synthetic analogue of PGF2α. The synchronization must be done after strict control of mating.