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Intramuscular injections of various levels of prostaglandin F(2alpha) were administered to 116 pregnant swine in three commercial herds and the University research unit on Day 111, 112 or 113 of gestation. Sixty-three percent of the treated animals farrowed during the working day immediately following treatment. The parturition time, birth weight, litter size, number of piglets weaned, growth of the piglets to weaning and subsequent rebreeding of the dams were comparable with the expected performance in the herds. The results indicated that prostaglandin F(2alpha) in doses ranging from 5 to 12.5 mg per animal were effective for induction of parturition in a substantial proportion of the treated animals. Successful induction of parturition could reduce the farrowing interval for batches, allow more supervision of farrowing, facilitate transfer of piglets from large to small litters and generally increase efficiency in the farrowing unit. This technique could have practical application in intensive swine production units.

Pregnant gilts and sows were given a single intramuscular injection of from 5-10 mg of prostaglandin F2alpha-tromethamine salt (dependent on liveweight) on day 111, 112 or 113 of pregnancy (first day of estrus = day 0) to induce parturition. When injected on day 111, 44% of the pigs farrowed within 40 hours compared with 93% injected on days 112 or 113. The mean time to the induced parturition was 27.3 +/- 4.7 hours. Signs of discomfort were observed during the first hour posttreatment but there were no apparent effects on lactation or on the mothering ability of the dams after farrowing.