Induction of parturition in swine and epostane, a competitive inhibitor of 3 beta-hydroxysteroid dehydrogenase.

The ability of epostane, a competitive inhibitor of the 3 beta-hydroxysteroid dehydrogenase (3 beta-HSD) enzyme system, to decrease the peripheral levels of progesterone and induce sows to farrow was examined. Twenty-five sows were randomly divided into five groups. On d 109 of pregnancy, each sow received one of the following treatments: no epostane (Group C); one oral dose of 5 mg (Group O5) or 10 mg (Group O10) of epostane/kg of body weight; or a sc injection of 1 mg (Group I1) or 5 mg (Group I5) of epostane/kg of body weight. During the 24 h after treatment with epostane, the levels of progesterone were approximately one-half of pre-treatment levels. Progesterone was influenced (P less than .01) by treatments and time. The treatment X time interaction (P less than .05) appeared to be due mostly to the difference in response between the sows that received epostane or vehicle. Similar results were observed for estrogen. The interval from treatment to the birth of the first piglet for Groups C, O5, O10, I1 and I5 was 112, 31, 33, 77 and 32 h, respectively, and the intervals differed (P less than .01). Three gifts in Group I1, with an interval of 53, 124 and 133 h, were not considered to have been induced. The route of administration of epostane or dose did not influence (P greater than .05) the interval to the onset of farrowing. The interval from the birth of the first to the last piglet in a litter, the proportion of piglets born live and weaned, and the birth and weaning weights for the five groups were similar (P greater than .05). These results suggest that inhibitors of the 3 beta-HSD can be used to induce farrowing without adversely affecting either the sow or its litter.