(1) Purified swine fsh and lh effectively induced superovulation in mature and immature as well as pregnant bovine females. Sixty-one of seventy-five treated cows and calves ovulated, producing a total of 1716 ovulation points which ranged from one to eighty-eight with a mean of 28·13. Twenty-eight of thirty-two cows and thirty-three of forty-three calves responded to treatment by ovulating. Calves produced an average of 12·46 more ovulations than did cows. (2) Neither the addition of prolactin to the ovulatory dosage of lh nor the administration of lh for 2 consecutive days proved superior to the single injection of lh as an ovulatory procedure for calves. (3) Calves produced 54·03% of their total ovulations on the right ovary compared to 51·17% for cows. (4) Nineteen cows, having undergone oestrus synchronization, produced an average of 7·89 ovulations more than were produced by nine similar individuals, superovulated without prior treatment with progesterone. (5) 60·21% of all cows superovulated demonstrated oestrus. A significantly greater number of cows receiving progesterone as well as those undergoing enucleation of corpora lutea exhibited oestrus than did cows not receiving treatment prior to superovulation. (6) Superovulated cows exhibiting oestrus produced an average of 3·82 ovulations more than were produced by superovulated cows failing to show heat.
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