THE EFFECTS OF GNRH AND CARAZOLOL ON OVUL ATION AND PREGNANCY RATES IN COWS

The effects of the intramuscular injection of the gonadotropin-releasi ng hormone (GnRH) analogue ''Buserelin'' and the intravenous administr ation of carazolol, 30 minutes before insemination, on the ovulation a nd pregnancy rates were investigated. The study involved 335 cows whic h were clinically normal at the time of artificial ir?semination. Cont rol animals received physiological saline. Milk samples were taken on days 0, 3, 5 and 7 of the oestrus cycle and examined in a progesterone assay. Of the 133 animals treated with carazolol, 14.2% exhibited del ayed ovulation as determined by rectal examination. Of the 85 animals treated with GnRH 16.5% exhibited delayed ovulation compared with 18.8 % in the control group. A strong correlation was found between the res ults of rectal examination and hormone assays in determining the resul ts of ovulation. Of the 85 animals treated with GnRH 70.5% were diagno sed as pregnant by rectal examination compared with 70.7% in the caraz olol treated group and 61.5% in the control group. These differences w ere not statistically significant, but indicate a strong positive effe ct of the treatments. In animals with delayed ovulation the conception rate in the carazolol treated animals was 63.2% compared with 64.3% i n rite GnRH group and 45.4% in the control animals.