Evaluation of the effects of route of administration of cloprostenol on synchronization of estrus in diestrous dairy cattle.

Cloprostenol was administered IV or IM to diestrous dairy cows to study luteolysis and synchrony of estrus and ovulation. In Study 1, 28 Holstein cows were assigned to receive injections of cloprostenol, IV or IM, on day 8 or 10 of the estrous cycle. Differences in cloprostenol-induced luteolysis or interval to estrus, were not detected. Ultrasonography revealed that 2 cows treated IV on day 8, 1 cow treated IM on day 8, and 2 cows treated IV on day 10 did not ovulate despite evidence of an apparently normal estrus. In Study 2, 20 Holstein cows were assigned to receive cloprostenol injections, IV or IM, on day 10 of the estrous cycle. Interval to estrus was not affected by route of administration. Analysis of these data indicated that cloprostenol given IV did not alter luteolysis or improve synchrony of estrus and ovulation when compared with cloprostenol given IM.