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Luteal Function and Embryo Survival in the Bovine¹

Animal Husbandry Department, Cornell University, Ithaca, New York

ABSTRACT

The ability of oxytocin injections to inhibit the development of the corpus luteum in the bovine was utilized to study the relationship between progesterone content of luteal tissue and embryo survival at 15 days after insemination in 70 Holstein heifers.

Twenty of 27 untreated heifers (74.1%) had normal embryos and the average total progesterone in their corpora lutea was 270.2 µg. The corpora lutea of the seven untreated heifers from which embryos were not recovered had an average of 304.1 µg. of total progesterone. Eighteen of the 43 heifers (41.9%) injected subcutaneously with 7 U.S.P. units of oxytocin per hundred pounds of body weight per day had normal embryos and the average total progesterone content of their corpora lutea was 310.6 µg. The total progesterone levels in the corpora lutea were not significantly different among these three groups of heifers.

Fifteen oxytocin-treated heifers had a precocious ovulation prior to the 15th day and no embryos were recovered from this group; their corpora lutea contained only an average of 45.8 µg. of total progesterone (P < 0.01). The remaining ten oxytocin-treated heifers had no embryos and their corpora lutea also contained significantly (P < 0.05) less total progesterone (154.1 µg.) than the treated heifers having embryos.

The level of ⁴-pregnene-20-ß-ol-3-one was significantly (P < 0.01) higher in the corpora lutea of the untreated animals without embryos than in any other group.

The data suggest that a threshold level of progesterone production represented by a luteal progesterone level of the order of 100 µg. is necessary for embryo survival at the 15th day.

The four of 15 oxytocin-treated heifers that ovulated precociously without showing signs of estrus had little or no measurable progesterone in their corpora lutea.

¹ Supported in part by funds provided by the regional research project, NE-41 entitled Endocrine Factors Affecting Reproduction and Lactation in Dairy Cattle, a cooperative study by Agricultural Experiment Stations in the Northeast and the Dairy Husbandry Research Branch, ARS-USDA.

² Present address: Department of Endocrinology, William S. Merrell Co., Division of Richardson-Merrell, Inc., Cincinnati 15, Ohio.