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Genetic Aspects of the Production Registry Program

U. S. Department of Agriculture

Abstract

Weaning reports from herds completing all requirements of the official Duroc Production Tested Herd Program in 1949 and in 1950 were studied to learn the relative influence of heredity and environment on the total variance of sow productivity. The data consisted of 869 litters from 31 herds in 1949 and 690 litters from 30 herds in 1950. Separate analyses were conducted on each group of data.

Environmental factors had important effects on the three traits studied in both 1949 and 1950, but had larger effects in 1949. Herd effect was considerably more important than age of dam for all traits and was greatest at weaning. Age of dam had the greatest effect at birth, but also had an important effect on weaning weight. Season had little effect on any trait in either year.

Age of dam seemed to have a curvilinear effect on litter size at birth. Litter size increased rapidly from 10 to 24 months, and then less rapidly until a peak was observed at 36 months.

Intraherd repeatabilities of litter size at birth and at weaning and of litter weight at weaning were 0.25, 0.16 and 0.07, respectively.

¹ Regional Swine Breeding Laboratory, Swine Research Branch, Animal Husbandry Research Division, ARS, U.S.D.A., Ames, Iowa.

² Gratitude is expressed to the United Duroc Swine Registry, Peoria, Illinois, for providing the data used in this study.