The Effect of Reduced GnRH Dose on Ovulation and Follicular Dynamics in Ovsynch Programme of Pure and Bunaji-Crossbred Cows.

Abstract

Our objective was to compare the efficacy of reducing GnRH dose from 100µg to 50µg on the formation of ovulation and sizes of ovarian structures following Ovsynch in apparently healthy Bunaji and Friesian × Bunaji Cows. Thirty female multiparous-apparently-healthy adult [Bunaji (n = 15) and Friesian × Bunaji (n = 15)] breeds of cattle were used. Five cows each were allocated randomly to three groups [control; full dose (FD), and half dose (HD)]. Cows in the control group were treated with 2ml normal saline while FD-group received 100µg lecirelin on day 0, with 500µg clorprostenol on day 7 and with 100µg lecirelin two days later. Furthermore, HD-group received the same treatment as FD-cows but the dose of lecirelin was reduced to 50µg at both times of GnRH administration. Ovarian structures were monitored by ultrasound with a 5-MHZ linear transrectal probe on days - 1 to 12. The ovarian responses of the various groups to first GnRH administration showed (0%, 40% and 60%) ovulation rate for C, HD and FD groups respectively in Bunaji breeds while in Friesian × Bunaji, it was (0%, 60%, 60%). Following second GnRH administration ovulation rate for Bunaji was (20%, 60%, and 60%) for Control, HD and FD-groups, respectively, while for Friesian × Bunaji cows it was (20%, 60%, and 80%). There was no significant difference (p > 0.05) in the days of new follicular wave emergence following the first GnRH administration. It was concluded that 50µg Lecirelin reduced the cost of drug without affecting the efficiency of Ovsynch protocol.