A study of factors affecting preweaning traits in inbred and linecross swine

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Virginia Polytechnic Institute


The aim of the study was to determine the differences between inbred and linecross litters in litter size and litter weight at birth, 21 and 56 days of age. The effect of line of dam, age of dam and year of birth on each of the production traits was also studied. Data comprising 556 litters (229 inbred and 327 linecross) from seven inbred lines developed by the U.S.D.A. at Beltsville were analyzed by the method of least squares. There were no differences between the inbred and linecross litters for number farrowed, but highly significant differences (P<0.01) were observed for all other traits. The lines of dam differed considerably in performance; the L-LB line gave the largest and heaviest litters and the L-CW line the smallest and lightest litters at each of the three ages. Age of dam at farrowing was the most important single factor affecting both litter size and weight. It accounted for 70 percent of the variation in both traits at birth and about 50 percent at weaning. Sows weaned litters, which were 2.4 pigs larger and 119 pounds heavier than those weaned by gilts farrowing under one year of age.