Estrous and ovarian responses following the administration of different insulin doses following progestagen-cloprostenol treatment in mated does during the dry season

Thirty-nine nulliparous and cyclic free-ranging Anglo-nubian goats were synchronized using 60 mg MAP intravaginal sponges for 10 days and 50 μg cloprostenol treatment, 48 h before sponge removal (SR). Goats were allocated to 3 groups with 13 animals in each group. The treatment groups, Insulin 0.14 and Insulin 0.20 were treated subcutaneously, for 3 consecutive days - beginning 48 h before SR, with 0.14 IU/kg BW/day or 0.2 IU/kg BW/day of a long-acting insulin, respectively. The Control group received a 0.5 ml saline solution (s.c.). The goats were monitored for the occurrence of estrus and mated at the onset of estrus and 24 h later. Transrectal ultrasonography was used to monitor the ovarian follicular dynamics, ovulation rate and diagnose pregnancy. Blood samples were collected from 48 h before SR to the 12th day of pregnancy for plasma insulin determinations. Insulin administration exhibited an increase (p < 0.05) in animals with plasma insulineamia. Insulin treated goats recorded a higher (p < 0.05) ovulation rate, when compared to saline control treated goats (1.7 ± 0.23 vs 1.0 ± 0.21). Nulliparous does from the Insulin 0.14 group recorded large follicles at 0, 12 and 18 h of the estrous period (p < 0.05), a more efficient synchronization of ovulation (p < 0.05) and larger size CLs (p < 0.05). It was concluded that administration in insulin induced a positive effect on ovarian response in nulliparous goats. Furthermore, in these animals the reproductive performance appeared to be independent of the increase of insulin dosage.