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University of Wisconsin, Madison 53706
Abstract
Data from three generations of a selection experiment with Yorkshire swine were analyzed. Fraternity size was defined as the number of sibs at 2 weeks of age. In one line, potential replacements were reared in fraternity sizes initially set at six, while in the other two lines fraternity size was not altered. Over the period of study, gilts reared in small fraternities (mean = 5.77) averaged 11.30 pigs born, whereas gilts reared in an unaltered fraternity size (mean = 10.06) averaged 10.19 pigs born. Both of these lines had experienced two generations of selection for increased litter size. A randomly selected control line in which fraternity size (mean = 7.80) was not altered averaged 10.77 pigs born. Gilts reared in small fraternities were heavier at 21 days, but there were no significant body weight differences between lines at breeding or farrowing.
1 Paper no. 744 from Dept. of Meat and Anim. Sci. Research supported by the College of Agricultural and Life Sciences. Contribution to the Regional Swine Breeding Project NC-103.
2 I am grateful to Drs. L. R. French, A. B. Chapman and M. Lorraine Leibfried for critical comments on a draft of this manuscript. The technical assistance of Mr. A. Gerbitz is gratefully acknowledged.
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