Abstract:
Animal Production in Australia 1998 Vol. 22 SUBJECTIVELY ASSESSED WOOL STYLE FOR SHEEP GENETICALLY DIFFERENT IN STAPLE STRENGTH A.N. THOMPSON and J.C. GREEFF Agriculture Western Australia, PO Box 757, Katanning, WA 6317 Wool from sheep selected for high staple strength (SS) has significantly less variation in diameter (Thompson and Hynd 1998) and length (A.D. Peterson unpubl.) between individual fibres than wool from sheep selected for low SS. We tested the hypothesis that these differences in fibre diameter variation would influence certain wool style attributes, such as handle and crimp definition. Hogget ewes (n = 224) from the SS selection flocks (Agriculture Western Australia) were grazed under normal conditions at the Great Southern Agricultural Research Institute in Katanning. One week prior to shearing (November 1996), the midside region of each ewe was assessed by two experienced wool growers, and scored for handle, colour, lock, crimp definition, dust penetration and condition. A mid-side sample was then taken and used to determine yield, mean and variation in fibre diameter, staple length and strength, and position of break. As expected, sheep from the sound selection flock produced stronger (P<0.001) wool with a lower standard deviation and coefficient of variation of fibre diameter (P<0.001) than sheep from the tender flock (Table 1). Wool from the sound flock tended to be softer to handle (P = 0.08), and had better crimp definition (P<0.01), than wool from the tender flock. All other objectively measured and subjectively assessed fleece characteristics did not differ significantly (P>0.05) between selection flocks. Table 1. Fleece characteristics for staple strength selection flocks Fleece characteristic Tender (n = 73) Staple strength (N/ktex) Fibre diameter variation s.d. (�m) c.v. (%) 21.8 4.55 25.7 3.32 2.70 a a a a a Selection flock Control (n = 66) 24.1 4.12 23.9 3.36 2.88 a b b a b Sound (n = 85) 31.5 3.73 21.1 3.50 3.06 b c c a c Handle (1 = harsh; 5 = very soft) Crimp definition (1 = poor; 5 = excellent) a, b, c: values with different superscripts differ at P< 0.05 The phenotypic correlations amongst wool characteristics differed significantly (P<0.05) between the two wool classers. Across all sheep, softer handling wool was characterised by a more distinct and even crimp (r = 0.28 and 0.63; P<0.001), and was whiter in colour (r = 0.48 and 0.59; P<0.001). Softer handling wool was also finer (r = 0.33 and 0.40; P<0.001) and less variable in fibre diameter (r = 0.50 and 0.52; P<0.001), although no significant correlations existed with SS. It is clear, at least for the wool classers used, that the correlations between certain subjectively assessed and objectively measured fleece characteristics were low to moderate at best. This indicates that indirect selection for fleece characteristics based on subjective traits would be much less accurate than selection based on objective measurement. It would appear that selection to improve SS genetically has no adverse effects on wool style attributes. THOMPSON, A. N. and HYND P. I. (1998). Aust. J. Agric. Res. (In press). 419