J. Anim Sci.
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J. Anim Sci. 1979. 48:1407-1421.
© 1979 American Society of Animal Science
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Proposed Mechanisms Controlling Parturition and the Induction of Parturition in Swine1

N. L. First2 and Michel J. Bosc3

University of Wisconsin, Madison 53706and Institut National de la Recherche Agronomique, Nouzilly, France

2 Address for reprint requests: Department of Meat and Animal Science, University of Wisconsin, Madison 53706.

Abstract

The initiation and completion of parturition in swine is dependent on the termination of progesterone production and the initiation of active processes bringing about expansion of the birth canal and the uterine contractions causing delivery. Evidence is presented to support the hypothesis that the fetuses initiate the sequence of events leading to delivery.

Present evidence indicates that the sequence of events leading to parturition start with pituitary stimulation of Cortisol production by the adrenal glands, followed by Cortisol causing stimulation of the production or release of prostaglandin F2{alpha}, probably by the uterus. Prostaglandin F2{alpha} was shown to cause luteolysis and release of relaxin from the corpora lutea as well as the release of oxytocin from the pituitary gland. It also caused stimulation of uterine contractions sufficient to bring about delivery. Parturition and lactation were both induced to occur prematurely by either prostaglandin F2{alpha} or the glucocorticoid, dexamethasone, and the results of field trials suggest that prostaglandin F2{alpha} or one of its analogs could be used to cause parturition to occur on a specified day.

Footnotes

1 Research supported by the College of Agricultural and Life Sciences, University of Wisconsin, Madison 53706. Department of Meat and Animal Science Paper No. 717.

3 Station de Physiologie de la Reproduction, Institut National de la Recherche Agronomique, Centre de Recherches de Tours, Nouzilly, France 37380.






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Copyright © 1979 by the American Society of Animal Science.