Seasonal variations in the dimensions of individual Romney wool fibres determined by a rapid autoradiographic technique

Abstract

A technique for radio-labelling short regions of growing wool fibres was modified by using intradermal injections of ³H-cystine and a rapid detection method. This technique allowed emergence times and dimensional changes of individual wool fibres to be rapidly and precisely monitored. Seasonal changes in fibre dimensions were determined for five sheep on maintenance nutritional levels following monthly injections over 12 months. Fibre diameter and length-growth varied seasonally, maximum and mimimum values occurring in summer and winter respectively. However, the amplitude and timing of each of these cycles differed between sheep and between fibres from individual sheep. As a consequence, the seasonal cycle in wool production (i.e., fibre volume) may be brought about by different combinations of fibre diameter and length-growth changes. Monthly diameter and length-growth measurements were often poorly correlated, suggesting that the cellular/physiological mechanisms determining these parameters in the follicle are complex.

Keywords:

• Romney sheep
• wool
• fibres
• autoradiography
• seasonal cycle
• wool production
• fibre dimensions