Refractoriness of Cows Repeatedly Superovulated with Gonadotrophins

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Abstract
Fifteen cows were superovulated repeatedly 2-6 times. Treatments were given during the follicular stages of the cycles. The sources of hormones included sheep pituitary FSH, unfractionated sheep pituitary gonadotropin, equine gonadotropin, human chorionic gonadotropin and hog pituitary FSH. In general, there was a decline in number of corpora lutea with successive superovulations. Limited data suggested that increased dosage partially but only temporarily overcame the refractoriness. Long periods without admn. of gonadotropins failed to eliminate the refractoriness. Assays of blood sera and other evidence indicated that antigonadotropins were not the cause of the reduced responses.

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