Changes in milk and plasma concentrations of progesterone in cows after treatment to induce superovulation and their relationships with number of ovulations and of embryos collected.

Progesterone concentrations in the milk of 86 Friesian cows induced to superovulate with an FSH-Cloprostenol treatment were studied daily from the day of estrus (D 0) to Day 7 (D 7). From D 2, a significant correlation between progesterone concentrations and ovulation rate was observed. Such a relationship was also observed beginning to D 3 between progesterone concentrations and the number of embryos recovered. No relationship was found between progesterone content and the number of viable embryos. For 30 of these cows, progesterone concentrations in blood plasma were also studied. The hormonal patterns in plasma and milk were similar but quantitative relationships were demonstrated earlier for progesterone in plasma than for progesterone in milk. It is concluded that relationships between milk progesterone concentrations and ovarian responses to a superovulatory treatment exist and could be of interest in embryo transfer programs in when predicting the number of embryos to be recovered.