Relationships between staple strength and other wool characteristics of Romney ewes

Romney ewes were offered pasture allowances of 0.7, l.2, l.7, or 2.2 kg dry matter (DM)/ewe per day for 6 weeks in June-July. Liveweight change, wool growth, fibre diameter, and staple length growth rate were measured during early and late winter and in spring. Fleeceweights were recorded at shearing in December and samples were collected for measurement of staple strength and assessment of soundness grade. Relationships between staple strength and subjectively assessed soundness grade and otherwqol measurements were examined. Increases in staple strength for a 1 gJday increase in wool growth in July-August were: Year 1,3.3 (SE = 0.5) N/ktex; Year 2, low allowance, l.8 (SE = l.2); Year 2, high allowance, 6.1 (SE = 0.9). There were also significant positive relationships between staple strength and both fibre diameter and clean fleeceweight. Ewes growing fleeces of low staple strength had a more pronounced seasonal pattern of wool growth than ewes growing sound fleeces, with the difference being most marked in July-August. Staple strength was not significantly associated with liveweight change, suggesting that variation in strength is caused by variation in the partitioning of nutrients to wool growth rather than to variation in intake.