Components of staple strength in fine and broad wool Merino hoggets run together in a Mediterranean environment

Abstract

Properties of fleeces and individual fibres were measured on 57 fine and 51 broad wool Merino hoggets, offered 1 of 3 supplementary feeding treatments, in an attempt to relate properties of individual fibres to staple strength. The fine wool hoggets (16·2 µm) grew wool of staple strength higher (2·5–4·3 N/ktex depending on feeding treatment) than that of the broad wool hoggets (20·1 µm). While there was no difference in the intrinsic fibre strength between the genotypes, the variation in diameter along fibres was 24% (P < 0·05) greater in the broad wool sheep. The broad wool sheep also grew fibres which were 50% stronger (P < 0·05) but 15% less extensible than the fine wool sheep. Staple strength increased (P < 0·05) from 8·6 to 24·9 N/ktex as supplementary feeding during summer–autumn was increased, for both genotypes. Increases in staple strength due to feeding were associated with a 3·3-µm increase in the minimum diameter along fibres (P < 0·05) and a 11·3-mN increase in fibre strength (P < 0·05). A multiple regression which included the coefficient of variation in diameter along fibres, and the extensibility of fibres, accounted for 62% of the variation in staple strength between sheep. The results enhance our understanding of the mechanisms which affect staple strength.