The use of sire and dam family averages in increasing the efficiency of selective breeding under a hierarchical mating system

Abstract

THE relative merits of individual selection and family selection in breeding for traits of incomplete heritability were first discussed by Lush (i 947) and, more recently, with particular reference to poultry breeding, by Lerner (r 950). The general conclusion is that for traits of low heritability, selection of complete families of full or half-sibs without regard to individual performance is more efficient than selection on the basis of individual phenotypes. For higher values of heritability the situation may be reversed, but in all cases maximum efficiency can be obtained by selection on the basis of a combination of family average and individual record.In poultry and other animal populations the family classification The first and second of these systems are discussed in detail by Lerner (1950, ch. XI) but neither of the others have been investigated, the nearest approach being the comparisons by Lerner and Lush of the relative merits of mass selection and half-sib family selection. These comparisons, however, neglect the full-sib relationship which exists between many pairs of a half-sib group in the above hierarchy. It is evident that the first three of the above systems are particular 93

Genetic and Phenotypic Parameters for Daily Gain and Body Weights in Suffolk Lambs

“…Corresponding correlations among lamb weights at 50 and 100 days were 0.89-r0.02 and0.'76. Selection for daily gain from 50 to I 00 days of age does not offer any advantage over selection based on lamb weight at 100 days when lamb weight at that age is the response criterion,,.similarity in the estimates of genetic and phenotypic parameters from 1980 Osborne (1957 Dickerson (1969 Bichard and Yalcin (1964) …”

Genetic and Phenotypic Parameters of Early Growth Traits of Lambs Reared Artificially in a Controlled Environment

“…The average relationship within progeny groups consisting of both full and half sibs were estimated according to Osborne (1957). The number of lambs and their sire and dams, and the average relationship within progeny groups of synthetic dam strains are shown in Table 4 for each lambing period.…”

Selecting young dairy bulls on differences between relatives and their contemporaries

“…Consequently, Figure 5 contrasts the last five or six years data, being more nearly a random sample of the population, with the data from earlier years being a more highly selected sample. Little is known about the distributions of components df variance or ratios of the components, Osborne and Paterson (1952). If it is assumed that the ratios used to estimate heritability and repeatability are normally distributed, ap proximate confidence limits can be computed for the estimates at a specified level of probability.…”