The influence of selection for greasy fleece weight on the components of fleece weight in Romney sheep : a thesis presented in partial fulfillment of the requirements for the degree of Master of Animal Science at Massey University

Abstract

Variation in the clean fleece weight (W) of New Zealand Romney sheep was related to variation in its four components: smooth body surface area (S), mean number of fibres (follicles) per unit area of skin (N), mean fibre cross-sectional area(A) and mean fibre length (L). The influence of the combined components, wool weight per unit area, fibre volume and total number of fibres (follicles) was considered. The contribution of the components to differences in fleece weight between the Massey fleece weight selected and control flocks was analysed using the "percentage deviation" technique. L was the most important contributor to fleece weight differences. The components of A and N were about equally important in contributing to between flock differences in fleece weight. By contrast, the contribution of S was relatively small. Wool weight per unit area had far more influence on fleece weight than body surface area (about 84% : 16%). Also, fibre volume made a greater contribution to between flock differences than the total fibre number. Attempts were also made to assess the relative importance of the components of fleece weight between ewes within each flock using either simple linear regression or multiple regression (standardized partial regression coefficients) techniques. Within both the selected and control flocks, A and S appeared relatively more important than between flocks, whereas, the L appeared to be less important, but the L seemed more important within the selected flock than within the control flock in determining the phenotypic differences in fleece weight between sheep.