RESUMO
The efficiency of cronolone sponges in combination with either pregnant mare serum gonadotrophin (PMSG) or cloprostenol (PGF2alpha) for inducing and synchronizing the estrous cycle in Turkish Saanen does was investigated during the transition from non-breeding to breeding season. All does (n = 80) were treated with 20 mg cronolone sponges for 11 days and divided into 4 equal groups. In addition, each doe received an intramuscular injection of either 1.5 ml sterile saline solution, 0.075 mg PGF2alpha, 500 IU PMSG or 500 IU PMSG and 0.075 mg PGF2alpha, 24 h before the sponge removal. Cervical artificial insemination (AI) with frozen-thawed semen was performed once 16 h after the detection of the first accepted mount. The total estrous response for the first 24 +/- 4 h, total estrous response within 96 h, time to onset of the induced estrus, duration of the induced estrus and pregnancy rate was found to be 75.0%, 97.5%, 31.4 +/- 1.2 h, 29.3 +/- 1.2 h, and 33.3%, respectively. There were significant differences between the first two groups and the last two groups in terms of the onset of induced estrus and estrous response at the first 24 +/- 4 h (P < 0.05). These results indicate that the use of cronolone/PMSG was more effective than cronolone/PGF2alpha in the attainment of early and compact induction of estrus in Turkish Saanen does.