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Effect of Feed Level and Parity on Ovulaton Rate in Three Genetic Groups of Swine^{1, 2,}

University of Wisconsin, Madison 53706

Abstract

NULLIPAROUS and multiparous sows of two breeds of swine (Yorkshire and Poland China) and their crosses were compared as to the effects of two levels of feeding on ovarian and related characters during an estrous cycle plus 2 or 13 days of the succeeding cycle. A greater ovulation rate was found in the Yorkshires than in the Poland Chinas and it was accompanied by heavier anterior pituitary glands, greater total numbers of follicles (day-13) and more medium follicles (day-13). Similarly, the difference between high and low feed levels in ovulation rate was parallelled by a difference in the weight of the anterior pituitary glands and follicular fluid weight (FFW) at day-2 and day-13. In addition, the difference in ovulation rate due to parity was accompanied by a difference in anterior pituitary gland weight. The means of the crossbreds for ovulation rate, corpora lutea weight, FFW (day-13), anterior pituitary gland weight, total numbers of follicles (day-13) and numbers of medium and of large follicles (day-13) were greater than those of the parental breeds and, in most cases, were equal to or exceeded the parent breed with the larger average. The Yorkshire breed, multiparity and high feeding level all showed higher ovulation rates and heavier anterior pituitary glands than the Poland China breed, multiparity and low feeding level.

¹ This work was done under a cooperative agreement between the Research Division of the College of Agricultural and Life Sciences, University of Wisconsin, and the Animal Husbandry Research Division, A.R.S., U.S.D.A., and supported in part by Cooperative U.S.D.A.-C.S.R.S. Grants No. 816-15-20 and 916-15-02. It was also supported in part by the Ford Foundation, Grants No. 63-505 and 63-0505A; and by the Program Project in Genetics, Grant No. GM 15422, from the National Institutes of Health. This is Paper No. 1529 from the Laboratory of Genetics and No. 605 from the Department of Meat and Animal Science.

² The authors wish to thank J. B. Peters and R. S. Mallampati for collecting the data in 1968 and 1969, respectively. Also, to Alfred Gerbitz for care and management of the experimental animals.