Heritability Estimates of Sow Productivity and Litter Performance1

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Abstract
Data on 561 litters raised in the Nebraska Swine Breeding Project from 1937 through 1943 were used to study the effects of age of sow, inbreeding of sow and litter on seven sow productivity and performance factors. The seven factors studied were: total number of pigs farrowed; number of pigs born alive; number of pigs alive at 21, 56, and 168 days of age; total weight at weaning, and 168 days of age. From the simple within line-season subclass regressions it was found that age of sow was more important than either inbreeding of the sow or litter in affecting sow productivity and performance. The standard partial regressions also indicate that age of sow was the most important factor affecting the sows' performance, but inbreeding of the litter became increasingly important as the pigs grew older. Heritability of the factors measuring sow productivity and performance were estimated from intra-sire regression of daughter on dam and regression of a sow's second litter on first litter. The average of these estimates was for total number of pigs farrowed, 0.24; for number of pigs born alive, 0.22; for number of pigs alive at 21 days, 0.27; alive at 56 days, 0.22; alive at 168 days, 0.37; for litter weight at weaning, 0.37; and for litter weight at 168 days, 0.18.
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