Ovum fertilization and embryo survival in ewes treated with estradiol immediately prior to mating.

Eight ewes in each of four groups were injected subcutaneously immediately prior to natural mating with 0, 30, 150, or 750 /ag of estradiol-17/3. The ewes were necropsied 3 days after mating and the ova were examined. None of the three doses of estradiol reduced ovum fertilization significantly, but the 750-/ag dose decreased the number of accessory sperm ceils in the zonae pellucidae. Eight other ewes in each of four groups were treated with the same doses of estradiol-173 and necropsied 25 days later. None of the estradiol treatments significantly reduced the rate of pregnancy. The results indicated that doses of 30 or 150 /ag of estradiol, injected immediately prior to mating, were not detrimental to sperm transport, ovum fertilization, or embryo survival for 25 days. The dose of 750 ~tg of estradiol may have reduced the efficiency of sperm transport. (