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A method and composition are provided for extending the gestation period of a sow so as to increase the live birth and survival rates of a swine litter without adversely affecting the sow. The method includes the step of administering an effective dosage of estrogen to the sow 21/2-7 days prior to the end of the expected gestation period for the sow. The composition administered includes from 0.5-10 mg of an estrogen selected from a group consisting of estradiol benzoate, estradiol valerate, estrone, estradiol 17β and effective mixtures thereof. The composition is adapted for administration parenterally by including a carrier such as corn oil. A method is also provided for synchronizing farrowing in a herd of swine bred following synchronized weaning so as to shorten the target period during which all the sows of the herd begin farrowing. This method involves the administration of a farrowing delaying composition including estrogen as an active ingredient in combination with the administration of an effective dosage of a farrowing inducing composition that may include a prostaglandin as the active ingredient.


University of Kentucky Research Foundation, Lexington, Ky.

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