Sequential changes of estrogens and progesterone at prostaglandin-induced parturition in the sow.

Parenteral administration of prostaglandin F2alpha (PGF2alpha) is efficient in inducing parturition in late pregnant swine. The purpose in the present study was to investigate the sequential changes of progesterone and estrogens at prostaglandin-induced parturition in the sow. Six of 7 sows (86%) treated once intramuscularly with 12.5 mg of PGF2alpha on days 110, 111, 112, or 113 of pregnancy farrowed within 39 hours after the injection. One PGF2alpha-treated sow and 2 sows given placebo injections on days 110 and 111 of pregnancy farrowed 90 to 130 hours later. The injection of PGF2alpha decreased the peripheral plasma concentration of progesterone in a manner similar to that observed immediately prepartum in normally farrowing sows. Estrogen patterns were similar in PGF2alpha-treated and control sows.