Rationalised classing of fine wools

R.N. Andrews and H. Hawker

Ruakura Animal Research Station, Ministry of Agriculture and Fisheries, Hamilton

Proceedings of the New Zealand Society of Animal Production. 1986, 46: 209-214

Fleeces from 2000 mixed age Merino ewes in each of 6 years were classed traditionally (i.e. by subjective assessment of fineness into 2 or 3 lines) or objectively (i.e. fleeces put into one line). Off-type fleeces (about 10%) which differed markedly from the bulk of the clip were excluded from all the lines. The fleeces from 800 to 1000 Merino hoggets in each of 6 years were also used in comparisons of traditional and objective classing.

The fibre diameter of each objective (OCP) line was very similar to the weighted mean of the corresponding traditional (TP) lines. Clean auction prices for the OCP lines were 0.8% and 1.0% lower than the weighted means of the TP lines for the ewes and hoggets, respectively.

Research in Australia has shown that there is no difference in the processing performance of traditionally or objectively classed lines of fleece wool. The optimum classing method is therefore determined solely by the relationship between price and diameter. Wools 21 µm and coarser should be classed objectively because the price v diameter relationship is stable and approximately linear. Objective classing of finer wools would be satisfactory in some years, but because the steeply curvilinear price v diameter relationship that can occur is not easily predicted, either objective or subjective methods of clip separation on mean fibre diameter are recommended.

Keywords: NZSAPAB; Fine wools; traditional classing; quality number; mean fibre diameter; objective clip preparation; clean wool price

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Last Updated 18-03-1997