Oestrus synchronization by hCG or hCG plus Prostaglandin in Appenninica x Bergamasca ewes at the end of seasonal anoestrus

The trail was carried out to evaluate the effectiveness of treatments with human chorionic gonadotropin (hCG) or hCG plus Prostaglandin F2à on oestrus synchronization in ewes. At the end of seasonal anoestrus 36 adult ewes (Appenninica x Bergamasca), kept separated from males for two months, were distributed equally into three groups: the firt (A) received three injection of hCG (250 I.U, i.m) at 8.00, 16.00, and 24.00 hr. On d-1 before male introduction, while the second group (B) received one injection of hCG (250 I.U, i.m) on d-9, followed by the administration of a PGFà analogue Cloprostenol on d-2 (0.125 mg i.m); while the third (C) was untreated (control group). All ewes were put together with the rams on d 0. Blood samples were taken from all animals at d-11,-2,+5,+10,+15,+20, and+30, progesterone plasma concentration was determined by RIA. Pregnancy was checked by echography at d+90 and the birth were recorted. At d-2 (1 st October 2003) nearly all the ewes (33/36) were anestrous (P4<0.8 ng ml) In the first group 9 ewes had fertile couplings in the first days after males rejoining and delivered within d+160 (A vs C:P<0.05) two ewes had twin births, three ewes became pregnant following the return of oestrus. In the second group 7 ewes had birth within d+160 after male introduction an done of them had twins, while 5 become pregnant on following oestrus returns. In the control group only 3 animals had births in the first 160 days after the male introduction while 9 ewes became pregnant on the following oestrus returns. Not one of them had twins. From these results we could conclude that a treatment with high doses of hCG may be useful to obtain synchronized fertile heats in anoestrus ewes.