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Synchronization of Estrus in Cattle with an Oral Progestational Agent and an Injection of an Estrogen^{1, 2,}

U. S. Department of Agriculture and University of Nebraska, Lincoln

Abstract

A technique for synchronization of estrus involving the feeding of a progestational compound 16-alpha-17-dihydroxyprogesterone acetophenonide (DHPA) and the injection of an estrogenic compound is described. Estrus was synchronized successfully by feeding 400 mg. of DHPA daily for 9 days and injecting 5 mg. of estradiol valerate on the second day of feeding. Estrus was synchronized in 95% of the 66 treated heifers and 54% of these heifers conceived when bred at the synchronized estrus, while 52% of the 33 control heifers conceived at first service. The amount of DHPA needed for control of estrus was reduced from 400 mg. per head per day to 75 mg. per head per day when DHPA was dissolved in sesame oil prior to mixing with feed. Estrus was successfully synchronized in cows by feeding 400 mg. of DHPA or 75 mg. of DHPA (dissolved in sesame oil) daily for 9 days and giving an injection of 5 mg. of estradiol valerate on the second day of feeding. Seventy-four percent and 77% of the treated animals were in estrus in a 3-day period while 72% of the controls were in heat in a 21-day period. Conception rate after one breeding at the synchronized estrus was 62% and 59%, while 83% of the controls conceived at first service.

¹ Published with the approval of the Director as Paper No. 2039 Journal Series, Nebraska Agricultural Experiment Station.

² This experiment was supported in part by a grant from E. R. Squibb & Sons, Inc., New Brunswick, New Jersey and Kern County Land Co., Bakersfield, California.

³ Present address: Department of Animal Science, Colorado State University, Fort Collins.

⁴ Fort Robinson Beef Cattle Research Station, University of Nebraska, Crawford, Nebraska.