Relationship between greasy and processed dark fibre contamination from Damara crossbred lambs in Merino wool

Abstract

Damara crossbred lambs were tested by SARDI for dark fibre as individual animals using staple wool (based on DTM-13-01) and core sampled as groups then worsted processed by CSIRO-TFT. The cores and tops were tested by AWTA Ltd. with the benzol method and the tops also tested by Centexbel using the Optalyser method (IWTO-55-99).

The combined fleece measurements for each batch were closely related to the dark fibre content of top measured by the benzol method and by the Optalyser. Single tests on core sample wool (20g) explained 97% of the variation in the benzol top test and 95% of the Optalyser test. Around 40% to 50% of the dark fibre in the core sample was detected in the top. This case study adds to evidence that presale testing of wool lots for dark fibre is feasible and also that dark fibre testing of tops could be undertaken with the benzyl method.

It is confirmed that contacts with Damara crossbred lambs can produce Merino wool contamination that persists in worsted processing to downgrade the quality of the top produced. This result substantiates a risk penalty applied for this breed type on farm within the Dark and Medullated Fibre Risk scheme.

The benzol and Optalyser dark fibre tests on top show close relationships with the combined dark fibre counts from testing individual fleeces using the CSIRO-DFD balanced lighting method (DTM-13-01) and with the benzol core test. Such clear relationships highlight the potential of the benzol method as a
means of determining dark fibre levels in greasy wool and tops. 

Citation

"Relationship between greasy and processed dark fibre contamination from Damara crossbred lambs in Merino wool", M.R. Fleet, A. Alaya-ay and T.J. Mahar, Report 02, Commercial Technology Forum, IWTO, Cairo Meeting, May 2006