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Further Studies on Factors Affecting Ovulation in the Cow¹

Cornell University³

Abstract

The effects of the administration of epinephrine, atropine, and atropine plus progesterone at the beginning of estrus on ovulation time in dairy heifers have been investigated.

Epinephrine administered at the beginning of estrus did not significantly hasten ovulation in 14 dairy heifers.

Atropine administered at the beginning of heat blocked ovulation in 69 percent of the cases.

LH in amounts sufficient to cause ovulation appears to be released from the adenohypophysis early in the heat period, although some individual variation in the exact time of release appears to exist.

Ovulation remained blocked in a considerable portion of the atropine-progesterone treated cows, suggesting that the previously found ovulation-hastening effect of progesterone in normal cows is not due to a direct action of progesterone on the anterior pituitary.

¹ Supported by funds from the regional project NE-1—"Causes and Prevention of Reproductive Failures in Dairy Cattle," a cooperative study by agricultural experiment stations in the north-eastern region and the Bureau of Dairy Industry, U.S.D.A.

² Research Officer, Central Experimental Farm, Ottawa, Canada.

³ Ithaca, N. Y.