Pigmentation relationships among young Merino sheep and their processed wool

Abstract

This paper reports the relationships between isolated pigmented fibres in hogget Merino fleeces, the levels of pigmented fibres in processed wool from these fleeces, and changes in various types of visible pigmentation in young sheep. The sheep sampled were hogget Merinos classed within paternal groups on the basis of indicators of isolated pigmented wool fibres in the fleece, forming 17 batches of fleeces processed to top (combed sliver). There was a strong correlation (r > 0.95) between the counts of pigmented fibres from measurement of the raw wool and the top. The concentration of pigmented fibres in top was at least equal to that found in the raw wool grid sample. Most of the pigmented fibres removed from the tops were assessed as having the potential to cause problems in wool processing. Sheep with pigmented leg fibres had greater amounts of other types of visible pigmentation than sheep without pigmented leg fibres, at 1 or more stages from birth to 18 months. There were also differences in agerelated changes in pigmentation associated with presence or absence of pigmented leg fibres. Presence of pigmented leg fibres was the best indicator of isolated pigmented wool fibres in the fleece and processed top; however, this positive relationship was evident only in progeny of sires with a high degree of expression of leg fibre pigmentation. In this sample of sheep, which were crutched to remove urine stain, classing based on leg fibre pigmentation alone was sufficient to keep the levels of pigmented fibres below the often-quoted upper limit of 100 dark fibres/kg for tops used for products in which dark fibres affect acceptability. Other types of pigmentation were also associated but provided little additional indication of isolated pigmented fibres in the fleece. Pigmented leg fibres will be readily discernible at crutching and shearing.