Genetic and phenotypic parameters for wool characteristics in fine-wool Merino, Corriedale, and Polwarth sheep. II. Phenotypic and genetic correlations, heritability, and repeatability

Abstract

Estimates of heritability, repeatability, and phenotypic and genetic correlations were calculated from data involving about 1050, 720, and 250 dam-daughter pairs for Merino, Corriedale, and Polwarth breeds respectively; data on daughters were taken at both 18 and 30 months of age. Phenotypic and genetic correlations in general were of the same order of magnitude and similar between breeds; the estimates substantiated the results obtained by other workers. Estimates of repeatability of most fleece traits between 18 and 30 months of age were significantly lower than estimates based on later ages. However, the differences were not large, and the use of a single figure for repeatability, either the younger age estimate or a pooled estimate, would give a reliable prediction for subsequent performance. Estimates of heritability of all traits in each breed were high; however, the heritabilities of greasy and clean wool weights of Merino and Polwarth ewes were about 40% smaller at 18 months than at 30 months, the estimates at 30 months being generally similar to previous estimates at 18 months. Relative to selection at 18 months, wool production, either greasy or clean, would increase at a greater rate per annum with selection of Merinos and Polwarths at 30 months; for Corriedales, selection at 30 months is more efficient for greasy, but not for clean wool production.