The relative importance of sources of variation in fibre diameter for Australian Merino sheep

Abstract

Variation in fibre diameter was estimated in five Merino strains under the headings: between sheep; between sites over the body of the sheep; between fibres within sites; and between points along the fibre. The variation between fibres constitutes some two-thirds of the total, and that between sheep, on which the classer can operate, is about one-fifth. By means of correlations between crimps per inch and fibre diameter together with selection differentials, the differences in fibre diameter which a classer is likely to achieve in making clips into two and three lines respectively were estimated. These were less than 1 µm in all cases. Between-line variances computed on the basis of these between-line ' differences in fibre diameter will reduce the total variance within a resulting line by fractions that are always less than 2%. It is concluded that the elimination of crimp-based classing should not produce bulk wools that are unacceptable on the basis of variation in fibre diameter.