Induction of estrus in cows by a new analogue of PGF2 alpha (alfaprostol)

A new analogue of PGF2 alpha, alfaprostol, was used to induce estrus in normally cycling and anestrous cows. Five groups of six animals were treated with single injections of different doses of the drug (4, 5, 6, 7 or 8 mg/animal) on day 10-11 of the estrous cycle. Six cows in anestrus, with palpable corpora lutea, were treated i.m. with 8 mg/animal. The luteolytic properties of alfaprostol were assessed by measuring milk progesterone by RIA for 96 h after treatment and by checking for the subsequent signs of estrus. The dose of 4 mg caused a slight fall in progesterone but did not induce heat; the 5 and 6 mg doses induced estrus in 3/6 animals and the 7 mg dose was effective in 4/6 animals. The 8 mg dose produced a sharp reduction in milk progesterone within 24 h, followed by estrus in both the normally cycling and the anestrous groups in 6/6 animals. No clinical signs of drug intolerance were seen. The present results show that alfaprostol might be of great use for both cycle synchronization in normally cycling cows and for treatment of anestrus caused by a persistent corpus luteum.