Size of dominant follicle, plasma progesterone and estradiol levels on the day of ovulation and subsequent conception rate in buffalo (Bubalus bubalis) following modified ovsynch + CIDR protocol

Abstract

The study was designed to compare the size of dominant follicle (DF) achieved, plasma progesterone decline and plasma estradiol level on the day of estrus and subsequent conception in buffaloes subjected to modified ovsynch-based regimen in buffaloes. In estradiol-based protocol (n = 15) on day 0 (beginning of experiment), buffaloes were administered controlled internal drug release (CIDR) device (1.38 g P4) and concurrently received 1.5 mg estradiol-17β in 1.5 ml canola oil (i.m.). On day 9, CIDR was removed and a PGF2α analogue (500 µg, i.m.) administered. On day 11, buffaloes were administered gonadotropin releasing hormone (GnRH) analogue (20 µg, i.m.) and inseminated on day 11 and day 12. Ovsynch-based group (control, n = 15) received GnRH on day 0 in place of estradiol-17β, CIDR insert for 7 instead of 9 days and the remaining protocol and insemination procedures were same as treatment group. The diameter of DF, plasma progesterone and estradiol levels were not different between the groups. The first service conception rate (FSCR) was higher (p < 0.05) in estradiol-based group than in control (53.33 vs. 33.33%, respectively). In conclusion, replacement of first GnRH with estradiol-17β in ovsynch plus CIDR protocol and increasing CIDR exposure by two days leads to higher FSCR.