Pregnancy Rate of Dairy Cows Following Synchronization of Estrus with Cloprostenol, hCG and Estradiol Benzoate

After assessment of luteal function by the milk progesterone test, oestrus was synchronized in 78 lactating Friesian cows with a luteolytic dose of cloprostenol which was followed by injection of hCG and estradiol benzoate 12 hours later. The cows were inseminated 48 hours after the injection of cloprostenol. Thirty-eight of the 78 cows became pregnant (48.7 per cent), compared with 59 of the 115 cows (51.3 percent) which were inseminated at natural oestrus. These results suggest that in dairy cows synchronized with cloprostenol, hCG and estradiol benzoate fertility is not altered.