Effect of steroids on ovarian follicle growth in river buffalo

Abstract

The purpose of this study was to control follicular growth using norgestomet implant along with steroids in river buffalo. The estrous cycle of females (n=12) was synchronized with two prostaglandin F2α analogue (PG; 15 mg, IM; Prosolvin®, Intervet, Holland) injections, 14 days apart. On Day 6 or 7 of the ensuing cycle (Day 0 of experiment), females received norgestomet implant (NORG; 3 mg; Crestar®, Intervet, Holland). Females received PG on Days 0, 1 and 13. On Day 5, females assigned randomly into three groups (n=4 in each group). The females of the 1st and 2nd groups received 2 and 5 mg estradiol benzoate (EB; Aburaihan, Iran), respectively, in association with 100mg of progesterone (PROG; Aburaihan, Iran). Group three females were did not receive any further treatment (control). The implant was removed on Day 14. Daily Ultrasonography was conducted to identify ovarian structures. In control group females, ovarian dominant follicle became persistent (PDF) and ovulation of PDF occurred within 64±8 hours after implant removal. In steroid groups, the injection of 2mg (Group 1) and 5mg (Group 2) EB along with 100mg PROG caused regression of PDF in 50% and 100% of treated females, respectively. The time of follicular regression (2mg: 5.5±1.5 days; 5mg: 5.5±0.87 days) and the emergence of the new follicular wave (2mg: 8 day; 5mg: 7.5±0.5 days) were not different between steroid treated groups (P<0.05). None of the treated animals in these groups had ovulation during 5 days after implant removal. In conclusion, 5 mg EB in association with 100 mg PROG results in a consistent follicle regression followed by an emergence of new follicular wave. However, steroids along with NORG may not be advised in river buffalo due to the ovulation failure after implant removal. This might be due to the high sensitivity of river buffalo to steroid treatments.