Superovulatory response of Sistani cattle to three different doses of FSH during winter and summer

Objective of the present study was to investigate the effect of season and dose of FSH on superovulatory responses in Iranian Bos indicus beef cattle (Sistani). Cyclic cows, in summer ( n = 16) and winter ( n = 16), were assigned randomly to three dose-treatment groups of 120 ( n = 10), 160 ( n = 12) and 200 ( n = 10) total mg of Folltropin-V with injections given twice daily for 4 days in decreasing doses. Estrous cycles were synchronized with two prostaglandin F 2α injections given 14 days apart. From day 5 after the ensuing cycle, daily ovarian ultrasonography was conducted to determine emergence of the second follicular wave at which time superovulation was initiated. Relative humidity, environmental and rectal temperatures were measured at 08:00, 14:00 and 20:00 h for the 3 days before and 2 days after the estrus of superovulation. Non-surgical embryo recovery was performed on day 7 after estrus. The effects of season, dose, time of estrous expression and all two-way interactions were evaluated on superovulatory responses: total numbers of CL, unovulated follicles (10 mm), ova/embryo, transferable and non-transferable embryos. Season (summer or winter), doses of Folltropin-V (120, 160 or 200 mg NIH) and time of estrous expression (08:00, 14:00 or 20:00 h) did not affect the number of transferable embryos (3.1 ± 0.58). When superovulatory estrus was detected at 08:00, a FSH dose effect was detected with the greatest numbers of CL (12.2 ± 0.87) and total ova/embryos (12.2 ± 1.46) occurring with 200 mg FSH (dose × time of estrous expression; P < 0.01).