Action on Dark Fibre Testing
On the 13th November 2002, AWTA Ltd announced to a seminar organised by the Federation of Australian Wool Organisations (FAWO) that it was planning to introduce a screening test for contamination of merino wool with fibres derived from contact with exotic sheep breeds. This service will be introduced in March 2003 and will be based on the CSIRO Dark Fibre Detector.
Research initiated by the South Australian Agricultural Research & Development Institute (SARDI) under the leadership of Malcolm Fleet, and collaborative research involving AWTA Ltd and SARDI, demonstrated that the presale coretest sample could be used to detect contamination of merino wool arising from contact of merino ewes with exotic rams, or contact between merino ewes and their lambs produced by matings with exotic rams(http://www.awta.com.au/Publications/Fact_Sheets/
Fact_sheet_018.htm).
The CSIRO Dark Fibre Detector was used for this research. This was possible because, unlike traditional black spot or urine stain contamination, the contaminating fibres tend to be spread over the fleece, and therefore relatively uniformly through lines of wool produced from contaminated sheep.
AWTA Ltd is planning to introduce a test for contamination of merino wool with fibres derived from contact with exotic sheep breeds. This service will be introduced in the first half of 2003 and will be based on the CSIRO Dark Fibre Detector. Vicki Senituli, Testing Officer, is pictured operating the equipment in AWTA Ltd’s Sydney Laboratory.
Towards the end of 2001, in response to industry concerns, CSIRO, AWTA Ltd and SARDI jointly submitted a proposal to Australian Wool Innovation Ltd (AWI) for funding for a project to develop a lower cost test method for dark fibre contamination from exotic sheep breeds.
In May 2002, AWI then decided to invite proposals from other researchers and on the 13th September 2002, announced that it would be providing funding for three proposals totaling AUD1.2M. A modified submission from CSIRO was among the three that AWI accepted. Inevitably this process has delayed the commencement of any research and development.
It will take time before these proposals achieve a successful outcome, but the potential contamination problem is with us now. The industry has been calling for a test for this type of contamination to be made available quickly. Recognising this, AWTA Ltd has decided to implement a service based on the existing technology, used in the research with SARDI, rather than waiting until newer, and hopefully less expensive technology becomes available.
In the early 1980’s a team from CSIRO led by Dr Roger Foulds developed an instrument for detecting pigmented fibres, dark fibres and medullated fibres in wool tops (Preparation and Dark Fibre Contamination, Clip Preparation Research, CSIRO Division of Textile Physics, September 1983 - a copy of this paper is available on AWTA Ltd’s website (http://www.awta.com.au/Publications/Research_Papers/
Wool_Contamination/Prep_DF_Contamination.pdf).
This instrument is very simple (see illustration above). Approximately 0.25–0.50 grams of fibre is spread thinly between glass plates and illuminated by dual sources of light – from above and below. The intensity of the illumination is balanced such that white fibres tend to merge into the background, while the objectionable fibres tend to stand out. The entire illuminated specimen is examined using 2x magnification. When a dark fibre is detected its colour can be categorised by reference to a scale, also developed by CSIRO.
Its limitation is that it relies on a painstaking examination of the illuminated sample by an observer. Due to the small amount of specimen (0.25-0.50 grams) that can be examined at one time, several (20-40) such specimens must be examined to achieve the level of sensitivity required. This means that the test is extremely labour intensive, each test requiring approximately 5 man-hours.
For the new service two technicians will visually examine two specimens, each of 10 grams, of washed core sample using the Dark Fibre Detector to identify the dark and medullated fibres present. These results will be reported to 4 levels: whether specimens contained >10 dark fibres (df) per test specimen (ts), 6-10 df/ts, 1-5 df/ts, or No Fibres Detected. A similar convention will be used for reporting medullated fibres.
As there is no IWTO Test Method for dark fibres in greasy wool, the test result will be issued as a Test Report, not as an IWTO Certificate.
AWTA Ltd has already taken delivery of 2 instruments and a further five are being obtained. For staff training and quality control reasons the Sydney Laboratory will initially provide the service, but it will be decentralised to Melbourne and Fremantle also. The cost per test will be AUD150 (plus GST). However, AWTA Ltd and CSIRO are collaborating on a modification of the technique that has potential to substantially reduce this cost.
At the FAWO seminar AWTA Ltd also suggested that the industry should re-examine the dark fibre risk analysis scheme developed by the CSIRO during the 1980’s. This scheme (see Features and Opinion sections for more details) used information provided by the wool grower to assign a level of risk of dark fibre contamination to each farm lot. This scheme used information such as breed, age, whether or not the sheep had been mulesed or crutched, and the time interval between crutching and shearing to provide an estimate of probability of contamination of a sale lot. It was developed for contamination by urine stain or by pigmented fibres growing on the sheep, but it should be relatively simple to extend it to incorporate contamination from contact with exotic sheep.
FAWO has taken this suggestion on board and has already sought funding by AWI towards implementing such a scheme. The involvement of an industry organisation such as FAWO is essential. Successful implementation will require co-operation by all segments of the industry, from wool growers to wool processors.