Influence of liveweight, liveweight change, and diet on wool growth, staple strength, and fibre diameter in young sheep

The effects of initial liveweight, liveweight change, and composition of the diet on wool growth and staple strength in weaner sheep were investigated. Weaner wethers (64) were allocated to treatments in a factorial design (2(3)). The factors were initial liveweight (heavy, 33 kg; light, 25 kg), liveweight change (fed at maintenance for 56 days, or 28 days at 0.6 x maintenance then 28 days at 1.6 x maintenance), and diet (lupin seed based diet or canola meal based diet). The heavier weaners grew approximately 1.9 g/day more wool than the light sheep during the experimental period and this resulted in a higher clean fleece weight (1.8 v. 1.4 kg), staple strength (37 v. 27.4 N/ktex), and fibre diameter (18.0 v. 17.4 mu m). Substituting canola meal for lupin seed increased wool growth during the experiment and clean wool yield, but did not affect clean fleece weight or staple strength. The weaners fed to lose and then gain weight grew wool with a lower staple strength than the weaners fed to maintain weight through the experiment (28.6 v. 35.8 N/ktex), but there were no differences in any of the other fleece characteristics. The ratio of wool growth to dry matter intake (DMI) was higher in the sheep fed canola meal than those fed lupins (by approximately 1.5 g/kg DMI) and higher in weaners losing weight than those fed to maintain weight (by approximately 4.5 g/kg DMI). From a practical perspective, these results indicate that initial liveweight and liveweight change both influence staple strength and wool growth and need to be included in any management strategy to improve wool quality of young sheep.