Exogenous steroid effects on litter size and early embryonic survival in swine

These studies confirm the efficacy of 12.5 μg estrone and 25 mg progesterone, administered on Days 16 and 17 of pregnancy, on increased litter size in swine. Substitution of estradiol (with ten-fold greater biological activity) for estrone in this regimen eliminated the positive effect on litter size and estradiol given alone at dosages of 3.1 and 6.3 μg were without effect. However, when estradiol was given in combination with progesterone (25 mg) at a dosage equivalent to 10% the effective estrone dosage (1.25 μg), a 22.6% increase in total pigs born per litter over controls was observed. Estrone alone at dosages of 6.25 and 12.5 μg did not alter litter size. At a dosage of 18.75 μg, an 8.7% decrease in total pigs born was noted. The amniotic fluid from sows treated for ten days with 12.5 μg estrone and 25 mg progesterone near the time of implantation, had significantly higher protein concentration, pH and osmolality.