Exogenous Progesterone and Estradiol Benzoate on Early Embryonic Survival in the Pig

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Abstract
The levels of exogenous progesterone and estradiol benzoate necessary for optimal embryo survival rates during early stages of pregnancy were determined in ovariectomized pigs. Gilts treated with a level of 80 or 160 mg of progesterone/100 kg body weight/day had higher embryo survival rates (65 and 58%; effects of estradiol benzoate held constant) than pigs given 40 mg/day (22%). Estradiol benzoate levels of 0, 125, 250, 500 and 1,000 µg/day did not significantly affect embryo survival rates. A daily injection level of 20 mg progesterone was inadequate for the survival of any embryo. With an adequate level of progesterone (80 mg), embryo survival rates at the highest level of estradiol benzoate (5,000 µg) were not significantly reduced. The treatment group given 80 mg progesterone and 500 µg, estradiol benzoate (160:1) had the highest average embryo survival rate (82%). There were significantly more nonviable embryos at day 25 of pregnancy in the gilts receiving a low level of progesterone (40 mg) than in those receiving higher levels (80 and 160 mg) and also in the gilts receiving a high level of estradiol benzoate (5,000 µg) than in those receiving lower levels (0, 125, 250, 500 and 1,000 µg). There was a positive correlation coefficient (r=0.64) between the number of dead embryos and the variance of the distance between the embryos. Copyright © 1973. American Society of Animal Science. Copyright 1973 by American Society of Animal Science.

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