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Abstract
A series of experiments was conducted to obtain information on factors associated with embryo death in swine. Two experiments were designed to investigate the effect of two feeding levels on ovulation rate and embryo survival. Increasing the feeding level from 1.81 kg. to 3.63 kg. per day for one estrous cycle before breeding resulted in an average of three more corpora lutea per gilt. A significant decrease in embryo survival was observed in animals receiving 1.81 kg. per day from the time of mating until slaughter at days 25 to 27, compared with animals receiving 2.72 kg. per day.
An experiment was conducted to investigate the effect of an orally active progestogen(MAP) on embryo survival and luteal function in limited-fed animals. Gilts receiving 0.91 kg. of feed per day plus 75 mg. of MAP had an average of 1.2 more embryos than did animals receiving 0.91 kg. of feed. Embryo survival was 89%, 79%, and 92% in animals receiving 2.72 kg., 0.91 kg. and 0.91 kg. of feed plus MAP, respectively. No significant differences were detected in luteal progesterone concentration. Animals treated with MAP had significantly less luteal tissue when compared with untreated gilts receiving 0.91 kg. of feed per day. Embryo survival in the MAP treated animals was strikingly uniform.
1 Journal Paper No. J-5203 of the Iowa Agricultural and Home. Economics Experiment Station, Ames, Iowa, Project No. 1325. This investigation was supported by USPHS Grants HD 01168 05 and HD 01168 06 and by the American Cyanamid Co., Princeton, N. J. Repromix was supplied by R. G. Zimbelman, The Upjohn Co., Kalamazoo, Mich.
2 Department of Animal Science.
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