Changes in fibre and follicle characteristics related to wool bulk during the lifetime of Perendale ewes

Wool and skin samples were collected annually at hogget shearing in October and thereafter in July for a further four shearings , from a total of 32 Perendale ewes born in 1990 and 1991 within lines selected for or against wool bulk. Time to form a crimp, f ollicle curvature and the proportion of para-meso cortical cells, increased towards an asymptote with increasing age. Proportion of fib res with a bilateral arrangement of cortical cells was maximal at 2 years of age and clean fleece weight, staple length and fibre diamet er were maximal at 3 years of age. Fibre curvature decreased linearly, crimp frequency and follicle length decreased curvilinearly but wool bulk did not change with increasing age. The repeatability of individual characteristics decreased with increasing age. There was no significant difference in the relationship between core bulk and a combination of fibre curvature, fibre diameter and fibre dia meter variation within each age group.