Prostaglandin-induced abortion in swine: Endocrine changes and influence on subsequent reproductive activity
Authors: Pressing A. L. , Dial G. D. , Stroud C. M. , Almond G. W. , Robison O. W. 
Published: February 2025

SUMMARY
Gilts were treated during midgestation with prostaglandin (pg) F to study the efficacy of different treatment regimens on induction of abortion and to determine the adverse consequences of pgf-induced abortion in swine. In study 1, pregnant purebred Duroc gilts (60 to 90 days of gestation) were given (im) 500 μg of cloprostenol (n = 12), 20 mg of dinoprost tromethamine (n = 11), or 10 mg of dinoprost tromethamine repeated 12 hours later by an additional 10 mg of dinoprost tromethamine (n = 11). The percentage of gilts that aborted and percentage of aborted gilts that returned to estrus for each treatment group were as follows: cloprostenol, 91.7% and 100%, respectively; 20 mg of dinoprost tromethamine, 36.4% and 25.0%, respectively; and 10 + 10 mg of dinoprost tromethamine, 100% and 90.9%, respectively.
Treatment with cloprostenol and with 10 + 10 mg of dinoprost tromethamine caused more gilts to abort (P < 0.01) than did treatment with 20 mg of dinoprost tromethamine. Gilts that did not abort were given a second treatment with 10 + 10 mg of dinoprost tromethamine. When the abortions by gilts initially treated with 500 μg of cloprostenol or 10 + 10 mg of dinoprost tromethamine were combined with those re-treated with 10 + 10 mg of dinoprost tromethamine, 32 of 33 (97.0%) gilts aborted, and 30 of the 32 (93.8%) aborted gilts returned to estrus. The gilts returned to estrus 4.9 ± 0.5 days after cloprostenol was administered and 6.2 ± 0.5 days after 10 + 10 mg of dinoprost tromethamine was administered. The farrowing rate (No. farrowed/No. bred) was not different (P > 0.05) between gilts induced to abort with either cloprostenol or 10 + 10 mg of dinoprost tromethamine (53.7%) and nonaborted gilts (63.6%) mated at similar ages and weights. Similarly, there was no difference in mean number of pigs born for pgf-aborted (7.0 ± 0.6) and nonaborted gilts (7.1 ± 0.6).
In study 2, 6 gilts were surgically fitted with indwelling jugular cannulae, and blood samples were obtained every 6 hours, starting before 500 μg of cloprostenol was administered and continuing until after the gilts had returned to estrus after they aborted. In 5 of the 6 gilts, serum values of progesterone (P4) decreased markedly, from > 10 ng/ml to < 1.0 ng/ml, by 30 to 54 hours after pgf was administered. After P4 concentrations reached a nadir, serum values of 17β-estradiol began increasing in each gilt and reached a peak just before preovulatory surge of luteinizing hormone. In the remaining gilt, P4 concentrations showed only a transient decrease of 12 hours’ duration, to < 4 ng/ml before returning to pretreatment values. A second treatment of this gilt with cloprostenol initiated a marked and persistent decrease in P4 concentrations. As in the other 5 gilts, this was followed by abortion and resumption of follicular growth, as indicated by increasing 17β-estradiol values, a preovulatory surge of luteinizing hormone, estrus. and ovulation. These studies indicate that exogenous pgf are potentially efficacious for terminating unwanted pregnancies and then allowing gilts to return to normal estrous cyclicity.