This field trial was perofmed to investigate the effects of early pp treatment with Gn-RH on ovarian activity and subsequ ent reproductive parameters in dairy cows. The study was carried out on 40 dairy cows between day 10 and 12 postpartum.
The cows were randomly assigned to two groups. The first group (24 cows) received I/M injection of 100 mcg Cystorelin (Gn-RH Abott laboratories, USA), while the second group (16 cows) received a placebo and served as control. Plasma progest erone levels were determined pre and post-treatment to monitor ovarian cyclicity and establishment of luteal function. The Cows were checked for oestrus and allowed freely for natural service and finally examined for pregnancy.
In the group that received Gn-RH, 91.7% of the treated cows showed ovarian cyclicity and ovulation occurred at 18.81+1.37 days pp compared to 68.8% and 28.90+2.44 days pp. in the control group respectively. The cows in the Gn-RH treated group conceived ater 82.50+3.04 days pp. Vs. 101.45+6.20 days in the control group. The plasma progesterone of cows prior to treatment was less than 1.0 ng/ml. while ten days after Gn-RH or placebo treatment, the values were 0.81+0.13 ng/ml. and 3.45+0.34 ng/ml. in the control and Gr-RH group respecti vely.