Studies of the effects of the gene N on body growth and fleece development of the New Zealand Romney. III. Fibre diameter and medullation

Abstract

Fibre and medulla diameters were measured of wool samples taken from N/ + and + / + Romney lambs at birth, at 6 weeks, and at 24 weeks of age. Relationships between fibre diameters and density were determined and also the changes in the proportions of kemps, medullated, and unmedullated fibres. From these results possible factors leading to the fleece type at 24 weeks mere analysed. In addition the relationships between medulla and fibre diameters mere calculated. The medulla diameter at a given fibre diameter was higher at birth and 6 weeks than at 24 weeks. At 24 weeks lambs showing poor body growth produced medullated fibres at a lower fibre diameter than did lambs growing well. The significance of these observations is discussed.