Reproductive performance of ewes treated with an estrus induction/synchronization protocol during the spring season
Anim Reprod, vol.8, n1/2, p.3-8, 2011
The aim of this study was to evaluate the reproductive performance of ewes treated with eCG and an exogenous progestagen protocol during the spring season. Forty-eight mixed-breed wool and hair ewes (body condition score of 2.8 ± 0.5 and 41 ± 3 kg) were randomly assigned into two groups (n = 24/group), which received (G-Sync) or not (G-Control) an intravaginal device (Day 0) containing 60 mg of medroxyprogesterone acetate. On Day 7, ewes of the G-Sync were injected with 300 IU of eCG and 30 ug of d-Cloprostenol, im. On Day 9, the device was removed and 12 h later males were introduced into the G-Sync and G-Control groups in a proportion of 1:6. Estrus response observation and mating were performed during Days 10, 11 and 12 from 7 to 9 AM and 4 to 6 PM. After Day 12, males were separated from females for 10 days and later reintroduced into the flock for 45 days. Estrus rates for the G-Control and G-Sync groups during Days 10, 11 and 12 were 4 and 88% (P < 0.05), respectively. Pregnancy rates from initial mating on Days 10, 11 and 12 were 0 (G-Control) and 46% (G-Sync; P < 0.05). Total pregnancy rates for the whole mating season were 50 (G-Control) and 79% (G-Sync; P < 0.05). The exogenous progestagen protocol plus eCG used for estrus induction/synchronization improved the pregnancy rate of mixed-breed wool and hair ewes by about 29% points at the end of the breeding season. Thus, this procedure seems to be appropriate to be implemented as part of the reproductive management of some ovine farms during the non-breeding season.
estrus induction/synchronization, ewes, pregnancy, spring season