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Effect of Human Chorionic Gonadotrophin on Maintenance of the Corpus Luteum and Embryonic Survival in the Cow

U.S.D.A. and Nebraska Agricultural Experiment Station^{,4, 5, 6, 7,}

Abstract

Daily injection of 1,000 I.U. of human chorionic gonadotrophin (HCG) into five cycling heifers from the 15th to the 26th day of the estrous cycle maintained the corpora lutea and lengthened the estrous cycle from 17.7 to 32.4 days. Thirty-nine bred heifers which received HCG from the 15th to the 35 th day post-breeding did not show an increase in pregnancy. However, regression of the corpus luteum in bred heifers subsequently diagnosed open occurred earlier in untreated than in treated heifers. It would appear that the embryo dies first and this results in regression of the corpus luteum. Injections of HCG resulted in formation of accessory corpora lutea in 67% of heifers diagnosed pregnant, 42% of the bred heifers diagnosed open and in none of the cycling heifers.

¹ Beef Cattle Research Branch, Animal Husbandry Research Division, ARS, Fort Robinson Beef Cattle Research Station, Crawford, Nebraska.

² Nebraska Agricultural Experiment Station, Fort Robinson Beef Cattle Research Station, Crawford, Nebraska.

³ College of Agriculture, University of Nebraska, Lincoln.

⁴ The technical assistance of D. G. Le Fever is acknowledged.

⁵ Published with the approval of the Director as Paper No.1129, Journal Series, Nebraska Agricultural Experiment Station.

⁶ Contribution from the North Central Regional Project NC-1, which is cooperative between the Agricultural Research Service, U. S. Department of Agriculture, the North Central Region and Oklahoma State Agricultural Experiment Stations.

⁷ Appreciation is expressed to A. D. Rankin for his helpful suggestions and to E. R. Squibb & Sons for partial support of this project and for the chorionic gonadotrophin.