Effects of Inbreeding, Selection, Linecrossing and Topcrossing in Swine. I. Inbreeding and Selection1

Abstract

A RENEWED interest in inbreeding as a means of improving livestock followed the rapid expansion of knowledge of genetic principles and the success of hybrid corn. This was one of the factors leading to the development of cooperative research on swine breeding methods between the U.S.D.A. and several midwest state experiment statioIls. Most of the efforts of the workers in this Regional Swine Breeding Laboratory during the first 15 years were devoted to developing and testing inbred lines, in order to measure the effects of inbreeding, the effectiveness of selection in offsetting the effects of inbreeding, and the performance of linecross and topcross offspring of the inbred parents. The Wisconsin Station developed and tested in various crosses five inbred lines, namely, three Chester White, one Yorkshire and one based on a cross of these two breeds. This report summarizes the data from this project on the effects of inbreeding and of the selection practiced in conjunction with this inbreeding. Copyright © . .