Effect of exogenous prostaglandin F2 alpha in clinically normal postparturient dairy cows with a palpable corpus luteum.

In 228 clinically normal cows with a palpable corpus luteum 20 to 40 days after parturition and a mean 305-day mature equivalent milk production of 8,970 kg, prostaglandin F2 alpha was administered in a randomized, controlled clinical trial to determine whether such treatment enhanced their subsequent reproductive performance. Although the treatment reduced median time to first breeding by 4.5 days (P = 0.0025) from 57.0 days, median time to conception was not significantly different between the treatment and nontreated control group (87.0 vs 88.5 days) and conception rate by 110 days after parturition was not significantly different (64.7 vs 69.6%). Use of prostaglandin was associated with a significant (P = 0.0459) decrease in conception rate at first breeding from 42.0 to 29.3%. This study suggested that prostaglandin treatment of cows with a normal reproductive tract and a palpable corpus luteum at a median of 25 days after parturition does not enhance their reproductive performance and thus is not cost-effective.