Experimental Tests of a Selection Index

SELECTION indexes have been advocated on statistical and genetical grounds as a means of combining information on several measured traits into a single selection criterion. Theoretically, it is expected that selection decisions based on such indexes would, under mass selection, give maximum genetic gains in terms of assumed economic values. Following initial derivations of selection indexes by Smith (1936) and by Hazel (1943), a large number of studies has been carried out with the aim of providing the genetic information necessary for constructing selection indexes. Sometimes indexes have been constructed based on simplified assumptions of economic variables. However, only a few applications of indexes have been reported (Manning, 1955; Dickerson, 1955; and Christian, 1957). Apparently, no experimental verification of the results anticipated under index selection is on record. This lack of experimental validation may reflect the convincing genetic and statistical arguments that have been made in favor of selection indexes, …