The 2003 Australian Wool Innovation on-farm fibre measurement instrument evaluation trial - Part 2: Performance in objective classing and ranking for animal selection

Abstract

This report summarises the results of the 2nd phase of a substantial trial carried out by Australian Wool Innovation Ltd. (AWI) in which the performance of the two common on-farm fibre diameter measurement technologies (OFDA2000 using midside samples and Sirolan Fleecescan using sampling of the whole skirted fleece) were compared with traditional midside sampling followed by laboratory fleece measurement, and with the outcomes of IWTO Certification of lots prepared using these technologies. In this phase, only Mean Fibre Diameter measurements were considered. The specific processes evaluated in this phase were the measurement-assisted classing of single mob wool clips, and the ranking of individual sheep. The evaluation was carried out on one superfine and one fine-wool property in Victoria, and a medium-wool property in South Australia.

The work illustrated that these two specific on-farm sampling and measurement technologies (i.e. OFDA2000 measurement on midside samples and Fleecescan measurements on the skirted fleece) produced very similar outcomes with slightly lesser precision than laboratory fleece testing carried out on midside samples in accordance with AS/NZS 4492. There was a strong relationship between the two onfarm technologies and their ability to measure Mean Fibre Diameter compared with certificate testing, and when used for fleece classing, they both produced lines of wool of different diameters in the expected order (i.e. the line that was expected to be finest was the finest, etc). Biases were observed between the expected classed line diameters and the certified test results (from –1.1 µm to +0.9 µm), and these varied from property to property. The phenomenon sometimes called "Micron creep" was similarly observed for both technologies and would also be expected to exist if laboratory measurements were to be used for fleece classing. From both the fleece classing and sheep selection results it can be concluded that the precisions of the two on-farm technologies for mean fibre diameter are near equal.

Finally, it was concluded that the larger the range in diameter within a flock, and the more precise the measurements, the more likely it is that classed lot measurements and animal selections using different instruments or systems will be consistent.

Citation

"The 2003 Australian Wool Innovation on-farm fibre measurement instrument evaluation trial - Part 2: Performance in objective classing and ranking for animal selection", J.W. Marler and P. Baxter, Report CTF02, Commercial Technology Forum, IWTO Evian Meeting, May 2004