Wool comfort factor variation in Australian crossbred sheep

Comfort factor (CF) is defined as the percentage of wool fibers with diameter less than 30 microns. Our objective was to investigate the effects of sire genetics, nutrition, level of supplementation and gender and their interactions on CF in crossbred sheep either grazing or supplemented with dietary protein. Correlations between CF and other wool traits were also investigated. Texel, Coopworth, White Suffolk, East-Friesian and Dorset sires were mated with 500 Merino ewes at a ratio of 1:100 in individual paddocks. Five hundred of the crossbreds were raised on pasture until weaning at 12 weeks of age. Forty of the weaners with initial BW range of 23-31 kg (average of 27 ± 3.2 kg) were fed with lupins or canola at 1 or 2% BW for 6 weeks in a 5 × 2 × 2 × 2 factorial experimental design. CF and other wool quality traits were commercially measured at the Australian Wool Testing Authority. Data were analyzed in SAS using MIXED models procedures with sire fitted as a random effect, whereas sire breed, nutrition, supplement, level of supplementation and gender and their interactions were fitted as fixed effects. We found that neither supplement (P > 0.14) nor level of supplementation (P > 0.16) influenced CF which did not differ between pasture-fed and supplemented sheep. However, highly significant effects of sire breed (P < 0.01), gender (P < 0.01) and interactions between sire breed × level of supplementation (P < 0.01), sire breed × gender (P < 0.03) and supplement × level of supplementation (P < 0.01) on CF were detected. White Suffolk crosses had the highest CF (90.1 ± 8.7%) and East-Friesian crosses the least (81.5±10.1%). Males fed canola at 1%BW had the highest CF (90.8 ± 7.0%), while females fed lupins at 1%BW had the least (81.1 ± 10.8). White Suffolk sired males ranked the highest (91.1 ± 10.5%) and East Friesian females the least (74.7 ± 7.9%). CF was significantly correlated with fiber diameter (−0.89), spinning fineness (−0.95) and wool curvature (0.33). Our findings provide useful information to sheep farmers in crossbreeding dual purpose sheep that will also deliver desirable wool comfort outcomes to the fabric industry.