Thirty-six female elk, determined by rectal palpation to be pregnant, were injected intramuscularly with 75-200 mg repository type diethylstilbestrol during the period December to March (3 to 6 months' gestation). Only about 30 percent of the pregnancies were terminated, it was learned by postmortem examination. The pregnancies of two elk injected with estradiol cyclopentylpropionate in the 6th month of gestation were terminated. Chemosterilants are usually effective for the year of treatment; succeeding pregnancies may occur unless the treatment is repeated. Precautions must be taken when chemosterilants are used on big game animals that may possibly be harvested by hunters. Cervical dilations and placement of intrauterine devices were unsuccessful. Bilateral ovariectomy was successfully performed on 33 pregnant and nonpregnant elk. A few pregnant elk were ovariectomized during each month from December to April and the time of abortion following surgery varied. When the management techniques of hunting, trapping, control shooting, or poisoning are for some reason undesirable, it may be that under some conditions herd regulation can be accomplished more effectively, precisely, and economically by ovariectomizing a number of cows at intervals of several years.
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文章 : 英语