The Effect of Inbreeding on Reproductive Fitness of S. C. W. Leghorns

Abstract

THE reproductive fitness of an animal may be defined as the number of its offspring reaching breeding age. When all birds in a breeding flock are given an equal opportunity to reproduce themselves, in the sense that the beginning and duration of the hatching season are held constant and that no young are culled, wide variation in reproductive fitness exists.This variation is of particular importance in the production of inbred lines, where selection for fitness may have to be practiced in order to prevent the reproductive rates from decreasing below replacement levels. Should the variation in fitness be dependent on the variation in the degree of homozygosity of either the parents or the offspring (thus producing differential rates of elimination), the accuracy of computed increases in homozygosity under inbreeding (the inbreeding coefficients) may be brought into question. The present study is designed to throw some light on this question, .