Hormonal augmentation of fertility in sheep: I. Induction of ovulation, superovulation and heat in sheep

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Abstract
1. Gonadotrophic extracts of horse-pituitary gland, of pregnant mare serum and of urine of pregnant women, as well as oestrogenic substances, will induce ovulation in anoestrous sheep. The number of ova shed is apparently independent of the dosage given and lies within the normal range.2. The oestrogens probably act by evoking ovulation-producing activity on the part of the animal's own pituitary gland, and it is likely that the gonadotrophins also initiate the same chain of events by causing oestrogen secretion by the ovary.3. Oestrogens induce heat in the anoestrous sheep, but horse-pituitary extract and P.M.S. evoked sexual receptivity only in animals having a regressing corpus luteum. In the absence of a corpus luteum, ovulation occurs without heat, while the presence of an active corpus luteum usually suppresses both ovulation and heat.4. Administration of horse pituitary a few days before the corpus luteum is due to regress results in superovulation at the succeeding heat, as many as twelve simultaneous ovulations having been obtained under these conditions.