RESUMO
Twenty-four cycling swamp buffaloes with normal reproductive histories and 2-3 months postpartum were used to investigate the effect of addition of estradiol-17 beta and human chorionic gonadotrophin (hCG) to the superovulation regime on the level of ovarian stimulation and embryo production. The estrous cycles of buffaloes were synchronized by prostaglandin injection and then divided into two groups for superovulatory treatment. Those in Group 1 (n = 12) received a implant containing 3 mg norgestomet (Syncro-Mate-B) for 9 days (insertion day is Day 0), with 4000 IU of equine chorionic gonadotrophin (eCG) and 500 micrograms cloprostenol i.m. given at Day 7. Group 2 (n = 12) received the same regime as Group 1, together with 7.5 mg estradiol-17 beta given in three intramuscular injections on Days 3, 5 and 7 in decreasing doses (4.0, 2.5 and 1.0 mg, respectively) and 5000 I.U hCG i.v. coincidentally with the first insemination. Estrus was monitored visually and by placing treated animals with bulls. Each animal was inseminated twice with frozen sperm after standing estrus. The numbers of corpora lutea (CL) and follicles greater than 8 mm in diameter were recorded via palpation per rectum at 6 days after implant removal. Two days later 11 animals from Group 2 and two from Group 1 were slaughtered for direct observation of ovarian responses and for embryo collection.