Milk progesterone concentration and production in superovulated Holstein cows.

Six Holstein cows in a commercial herd (three superovulated and three controls) and eight Holstein cows superovulated a total of 12 times in an experimental herd were studied. Superovulation was induced primarily by treatment with follicle stimulating hormone and prostaglandin F2 alpha. Milk was weighed twice daily for 30 days following treatment in the commercial herd with no effect on production. Milk samples were saved on Monday, Wednesday, and Friday to determine progesterone content. Last milk at mid-cycle averaged 8.2 ng/ml of progesterone for the cows in the experimental herd, and 7 days after superovulation they averaged 52.6 +/- 10.2 ng/ml (mean +/- standard error) of progesterone. The correlation with number of embryos recovered was .86. Therefore, milk progesterone may be useful in monitoring superovulatory response. Also, injection of prostaglandin F2 alpha into superovulated cows 9 days after a previous injection did not initiate a new estrous cycle, a fact accurately monitored by milk progesterone determinations.