Effect of Gonadotrophin Releasing Hormone on Follicular Dynamics, Luteinising Hormone, and Progesterone Levels in Bunaji Cows

Abstract

This study evaluated the ovarian and hormonal responses of Bunaji cows to ovsynch protocol initiated at random oestrus cycle stages. Fifteen animals were arranged into three groups and treated as follows: control (n=5), 2mL normal saline; group A (n=5), 50mg Gonadotrophin releasing hormone (GnRH) on day 0 and day 9 followed by 500mg of Prostaglandin F2 alpha (PGF2a) on day 7; and group B (n=5) 100mg of GnRH on day 0 and day 9 followed by 500mg PGF2a on day 7. Ultrasound examination of the ovaries was carried out daily from d 1 to d 9 and, thereafter every 12h until ovulation was detected. Blood sampling was carried out at 30 min intervals for 6 h following the GnRH administration for determination of serum luteinizing hormone (LH) and once daily for 12 days after the injection of the first GnRH to determine plasma progesterone concentration. The ovarian response of the treated groups showed no significant difference between the two dosages of ovsynch protocol but differed significantly between the treated and the control groups. Peak values of serum LH obtained on day 0 and day 9 of GnRH administration differed significantly (P<0.05). Plasma progesterone increased among treated groups following injection of GnRH reaching a peak on day 7 compared to control, but did not differ among treated groups. In conclusion, GnRH at 50 mg and 100 mg was able to elicit adequate LH and progesterone responses that caused the disappearance of dominant follicles and, subsequent ovulation thereby increasing the reproductive efficiency of Bunaji cows.