Abstract

Variation in the clean fleece weight (W) between ewe hoggets born in 1988 from the Massey University fleece weight selected (FW) and control (C) flocks was related to variation in four components: predicted skin surface area (S), mean number of fibres (follicles) per unit area of skin (N), mean fibre cross-sectional area (A) and mean staple length (L). Mean W (±pse) was 3.34 and 2.48 ± 0.07 kg for the FW and C lines, respectively. Of the components, L (147 and 126 ± 3.1 mm; P<0.001), N (29.6 and 27.0 ± 0.83 fibres/mm2; P<0.05) and A (1096 and 1002 ± 28.0 µm2; P<0.05) were significantly greater in the FW line (n=27) when compared to the C line (n=22). The difference in W between the two lines was apportioned into contributions from the various components using the percentage deviation technique. The influence of combined components, wool weight per unit area (N x A x L), fibre volume (A x L) and total number of fibres (S x N) on W was also examined. The most important contributor to the difference in W between lines was L with A and N being less important; the contribution of S was relatively small. Wool weight per unit area had far more influence on between line differences in W than wool growing surface area (S) and fibre volume was more important than the total fibre number. Attempts were also made to assess the relative importance of the components of fleece weight between sheep within each line. The standardised partial regression coefficients of log transformed values of each component on W were; for the selected line, L = 0.26, A = 0.36, N = 0.16, S = 0.38; for the control line, L = 0.08, A = 0.58, N = 0.45, S = 0.53. High values of S relative to the other components of W suggest that the size of animal is more important in determining the phenotypic differences in fleece weight within the line than the genetic differences between lines.

AH, Liu, GA Wickham, and HT Blair

Proceedings of the New Zealand Society of Animal Production, Volume 54, , 243-246, 1994