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The Heritability of Some Factors Affecting Productivity of Brood Sows¹

University of Minnesota

Abstract

THE RATE of improvement in livestock through selection depends upon the variation of the characteristic among the population, the proportion of each generation required for replacement, and the heritability of the characteristic or character. In the past many workers have devised different methods of determining "heritabilities" or estimates of the degree of inheritance of quantitative characters. These estimates measure the portion of the observed variance which is caused by differences in heredity or the degree to which quantitative characteristics are transmitted from parent to offspring. In doing this, as was first demonstrated by Wright (1920), one divides the total variation into that portion due to environ, mental causes and that due to genetic causes affected by additive genes.

The inheritance of quantitative characters is based largely upon the multiple factor hypothesis which deals with the effects of additive genes. However, one should not ignore the fact that gene interaction, epistasis, and doIninance are factors which likely pJay a role in the expression of these characters through inheritance.

¹ Paper No. 3336, Scientific Journal Series of the Minnesota Agricultural Experiment Station in cooperation with the Regional Swine Breeding Laboratory, Ames, Iowa, Bureau of Animal Industry, U. S. Department of Agriculture.Funds for the statistical analyses of this study were provided in part by a Grant in Aid of Research of the Graduate School, University of Minn.

² H. A. Stewart is Professor in the Department of Animal Industry, North Carolina State College. The authors are indebted to Mrs. Helen Feldman for her assistance in making many of the statistical calculations included in this paper.