T. S. Stahly

Effects of estrogen and prostaglandin on progesterone-delayed farrowing

Effects of estradiol benzoate and prostaglandin F(2alpha) (PGF(2alpha)) on concentrations of progesterone and estrogen in serum and the percentage of live births were determined in 21 gilts treated with exogenous progesterone in late gestation. All gilts received progesterone (25mg s.c. four times daily) from Days 108 through 113 of gestation. Gilts receiving no other treatments (controls) had elevated levels of progesterone through 1800 h on Day 114 (29.2 +/- 11.4 ng/ml) and farrowed at 115.6 +/- 0.3 d of gestation with a relatively low percentage of live births (66.8 +/- 17.3). Gilts treated with PGF(2alpha) administered at 0600 h on Day 114 had less (P<0.01) progesterone by 1800 h (7.0 +/- 1.3 ng/ml) relative to that of the controls, but they had similar gestation lengths (115.5 +/- 0.3) and percentages of live births (50.0 +/- 16.2). Administration of estradiol benzoate (10 mg) to gilts at 0600 h on Day 114 did not reduce progesterone on Day 114 or the gestation length relative to that of the control gilts, but it did increase (P<0.05) the percentage of live births (100%).

Serum progesterone and luteinizing hormone following prostaglandin F2α during the sow's estrous cycle

Abstract Thirty-six sows and gilts (hereafter called sows) received one of three prostaglandin F2α(PGF2α) treatments on day 6, 10, or 14 of the estrous cycle to determine the effect of prostaglandin treatment on subsequent concentrations of luteinizing hormone (LH) and progesterone. Also, the effect of treatment on estrous cycle lengths was evaluated. Blood was sampled every 15 min for 6 h. Starting from time 0, sows received 25 mg of PGF2α at 4 h (treatment 1), 50 mg at 4 h (treatment 2), or 25 mg at both 1 h and 4 h (treatment 3). Treatment and day of cycle that sows were treated modified estrous cycle lengths (P 0.05) among the three cycle stages nor altered by quantity of PGF2α although the response to a second injection (treatment 3) was diminished (P 0.05) at any time. Therefore, it appears that resistance of naturally occurring corpora lutea (of the estrous cycle) in swine to the luteolytic action of PGF2α is not due to gonadotropic support from the pituitary.