RESUMO
Serial progesterone injections followed by human menopausal gonadotropin (hMG), instead of equine chorionic gonadotropin (eCG), were used to synchronize estrus in ewes. Shal ewes (n = 189) were assigned into five groups and each group was divided into two sub-groups to receive gonadotropins including eCG (300 IU; intra-muscular) or hMG (one ampoule; subcutaneously, SC). All ewes received prostaglandin (PG) F2α six days after introducing ram (day 0). Ewes received 0 (control), one, two, three or four injections of progesterone (50.00 mg; SC), 72 hr apart. The first progesterone was injected at the time of PG injection. Ewes in treatment groups received gonadotropins 48 hr after the last progesterone injection. Control group ewes received gonadotropins, at the time of PG injection. Mating was recorded after introducing fertile rams. Data were analyzed using GLM and GENMOD procedures in SAS. The incidence of estrus was less in control and ewes received a single progesterone (34.20%) compared to ewes received two (64.10%), three (81.10%) and four injections (68.40%) of progesterone. Time to estrus was earlier in control (45.70 ± 4.41 hr) than progesterone-treated groups (63.60 ± 1.79 hr). Fertility (51.30%) and fecundity (78.40%) of ewes received three progesterone injections were significantly greater than other progesterone-treated groups. There was no significant difference in reproductive indices between eCG and hMG sub-groups. In conclusion, during the non-breeding season, three injections of progesterone, three days apart, starting six days after ram exposure, in association with hMG, 48 hr after the last progesterone injection, could provide a sound reproductive performance in Shal ewes.