Effect of Estrogen and Progesterone on Early Embryonic Mortality in Ovariectomized Gilts

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Abstract
Studies have been made on early embryonic mortality in swine. All ova recovered from eight bred gilts slaughtered 1 to 2 days after the end of estrus showed cleavage stages of two or more blastomeres. Thirty-three percent of the corpora lutea counted in 15 pregnant gilts at the 25th day after mating were not represented by normal embryos. The average embryonic mortality rate observed in eight gilts slaughtered on the 40th day of pregnancy was 38%. The effect of progesterone and estrogen, administered intramuscularly in sesame oil, on embryonic survival was evaluated in pregnant gilts ovariectomized on the 15th day after mating and slaughtered on the 25th day of gestation. Thirty-four ovariectomized gilts were injected with various levels of progesterone and estradiol benzoate daily during this 10-day period. The results obtained indicate estradiol benzoate alone will not maintain pregnancy in gilts and progesterone alone is not as effective in producing optimum intra-uterine conditions for embryonic survival as is a combination of progesterone and estradiol benzoate. Thirteen out of 17 ovariectomized gilts injected daily with 100 mg. of progesterone and 50 meg. of estradiol benzoate per 100 lb. of body weight were pregnant when slaughtered. The average embryonic mortality rate in these 13 gilts at 25 days of pregnancy was 22% or 11% less than that observed in 15 intact gilts slaughtered at the same stage of pregnancy. Copyright © . .

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