To make policy decisions in the light of a continually changing economic environment farmers need information on the effects of crossbreeding and time of shearing on wool characteristics. The changes in wool quality characteristics of Merino and Merino crossbred lambs, shed by Border Leicester, Poll Dorset, Oxford Down, Texel or Suffolk rams, were examined from 3 to 12 months of age. Clean wool yield declined over that period with the decrease being least for purebred Merino fleeces. Border Leicester cross fleeces were significantly (P<0.001) higher yielding than all other breeds. Staple length was greatest (P<0.001) for Border Leicester cross fleeces and least for Merinos and Suffolk crossbreds. Fibre diameter increased slightly throughout the year. Merino fleeces were significantly (P<0.001) finer than the crossbred fleeces. Loose wool bulk showed a significant increase with time (P<0.001). Bulk was greatest for Suffolk, Poll Dorset and Texel cross fleeces with Border Leicester cross and Merino fleeces having the lowest loose wool bulk (P<0.001). Brightness declined significantly throughout the year (P<0.001). Purebred Merino fleeces were consistently brighter than the crossbred fleeces (P<0.001). Both yellowness and staple strength showed no consistent trend throughout the year. Merino fleeces were less yellow than crossbreds. Texel crossbreds had the strongest and Border Leicester crossbreds the weakest fleeces (P<0.001). It is concluded that some wool characteristics change significantly throughout the first year of a lamb's life. Crossbreeding had large effects on wool traits but little effect on the changes from 3 to 12 months of age.
