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Use of Progestational Compounds Alone or in Combination with Estrogen for Synchronization of Estrus^{1, 2,}

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

Abstract

Three trials using injections of progesterone alone or in combination with an estrogen were conducted. In trial I two hundred twenty cycling, virgin heifers were synchronized with daily injections for 24 days of 20 mg. of progesterone alone or in combination with 10, 20 or 40 mcg. of estradiol or 40 mg. of progesterone alone or in combination with 20, 40, or 80 mcg. of estradiol.

Two other groups received the progesterone plus three injections of estradiol on the 23rd, 24th and 25th days. Synchronization varied from 70 to 100% of the heifers showing estrus in a 4-day period. Fertility was lowered at the synchronized estrus in all treated groups except in the group receiving 40 mg. of progesterone and 80 meg. of estradiol.

In trial II one hundred four cycling, virgin heifers were injected with either 20 or 40 mg. of progesterone and either 80 or 160 meg. of estradiol. Ninety-five to 100% of the heifers showed estrus in a 4-day period; however, fertility was lower than that in the controls. In trial IIIninety cycling, virgin heifers received a single injection of 62.5, 125 or 250 mg. of an acetophenone derivative of 16a, 17a dihydroxyprogesterone (AD) either alone or in combination with estradiol enanthate (ENT) in a ratio of either 250 or 500 parts AD to one part of ENT.

Another group of 120 heifers received either 75, 100 or 125 mg. of AD in a ratio of six AD to one ENT. Poor synchronization was experienced in all groups of heifers receiving a single injection. Inclusion of ENT in the injection at the higher level caused many short estrous cycles.

¹ Published with the approval of the Director as paper No.1677, Journal Series, Nebraska Agricultural Experiment Station.

² This experiment was supported in part by E. R. Squibb and Co. Their help is gratefully acknowledged.

³ Fort Robinson Beef Cattle Research Station, Animal Husbandry Research Division, ARS, U.S.D.A., Crawford, Nebraska.

⁴ Department of Animal Science, University of Nebraska, Lincoln, Nebraska.

⁵ The authors gratefully acknowledge the assistance of D. G. LeFever. who was responsible for carrying out many of the technical aspects of this experiment.

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