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Abstract
Induced ovulations were observed in gilts injected intramuscularly with Armour's Pituitary Gonadotrophin, FSH. The FSH was administered at levels ranging from 20 to 40 Armour Units per gilt. Five to 80 mg. of estradiol benzoate was injected intramuscularly 1 day after a FSH injection to induce boar acceptance in conjunction with induced ovulations. The exogenous estrogen had little effect in promoting estrus in gilts injected during the luteal phase of the estrous cycle, whereas estrus was induced by treatment during the early follicular phase.
Eight out of 16 gilts given a single injection of FSH at various stages of the estrous cycle showed boar acceptance 18 to 23 days after this hormone was administered. Sixty-five of 73 ova recovered from these gilts showed cleavage stages of two or more blastomeres.
Estrus was induced in ovariectomized gilts administered 0.2 mg. of estradiol benzoate per 100 lb. of body weight. However, estrus was not observed in animals receiving 1 mg. of this estrogen and a single injection of progesterone at the rate of 50, 100 or 200 mg. per 100 lb. body weight.
1 Journal Paper No. J-3485 of the Iowa Agricultural and Home Economics Experiment Station, Ames, Iowa. Project No. 1325. This work was carried out in cooperation with U.S.D.A., A.R.S., A.H.R.D., Regional Swine Breeding Laboratory.
2 Present address: Department of Animal Husbandry, University of Missouri, Columbia, Missouri.
3 The authors gratefully acknowledge the cooperation of Dr. Irby Bunding and Dr. M. E. Davenport of the Armour Laboratories, Kankakee, Illinois. This work has been supported by the Rath Packing Co., Waterloo, Iowa and Farmers Hybrid Hogs, Hampton, Iowa.
4 Department of Animal Husbandry.
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