Comparison of three Australian Merino strains for wool and body traits. I. Genetic means of studs and strains and their interactions with years and sexes

Abstract

Samples of breeding age rams and ewes were taken from seven studs representing three strains of Australian Merino, and run in a single environment at Hay, N.S.W. Measurements taken from the ram and ewe progeny of these sheep, born at Hay in 1964 and 1965, were used for a comparative study of wool and body traits of the seven studs. The traits measured were body weight, face cover, folds, greasy fleece weight, yield, clean fleece weight, quality number, character, handle, colour, staple length, crimp frequency, fibre diameter, fibre density, two estimates of the value of wool production per head, and the value of wool production per pound. Large strain and stud within-strain effects were present for both wool and body traits. Strain x year interactions in wool values were attributed to fluctuations in the wool market. Strain x year interaction in fibre diameter reflected variation between the strains in their response to changes in environment, as did stud within-strain x year interactions in greasy fleece weight, yield. and clean fleece weight. Strain x sex interactions were interpreted in relation to a proposed new classification of interactions. The amount of migration between pairs of studs was not related to the present genetic difference between them, for any trait. Schemes for extending the present study to a large number of studs are discussed. Preliminary results of selection experiments have suggested that strains may vary in their response to equal selection pressures.