Follicle characteristics, seasonal changes in fibre cross-sectional area and ellipticity in Australasian specialty carpet wool sheep, Romneys and Merinos

Abstract

Data was collected on secondary:primary follicle ratio, relative follicle density, and seasonal changes in fibre cross-sectional area and fibre ellipticity (ratio of major-to-minor fibre cross-sectional axis) in the Australasian specialty carpet wool breeds (Carpetmaster, Drysdale, Elliottdale, Tukidale), Romneys and Merinos. Merinos had a higher secondary:primary follicle ratio ( p<0.001), relative primary follicle density ( p<0.05), relative secondary and relative total follicle density ( p<0.01) than the other breeds. Both breed and follicle type (primary or secondary) had a significant effect on fibre cross-sectional area ( p<0.05). While both fibre types (primary and secondary) showed changes in cross-sectional area during the experiment, a more distinct seasonal pattern was seen in the secondary fibres with summer maxima and winter minima in all breeds. Relative change in fibre diameter was higher in secondary fibres than in primary fibres. Changes in fibre ellipticity were also noted throughout the duration of the experiment. It is apparent that there are differences between primary and secondary follicle populations in the way the fibres produced contribute to seasonal changes in average fibre diameter of fleeces. The changes suggest there are separate control mechanisms for each follicle type and that the number, size and arrangement of the cells in each type of fibre vary independently of one another throughout the year, bringing about dynamic changes in fibre growth and form. Further work is required to examine the influence of feed quality on these factors and to determine the mechanisms through which these changes in fibre structure are brought about.