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
is a hierarchical one, consisting of several sires each mated to a number
of dams and each mating producing several offspring. Various
schemes of family selection or combination selection are thus available