Dark and medullated fibre program
To minimise the spread of dark or medullated fibres and maintain Australia’s reputation for clean, white wool, automated wool testing is being developed to easily identify unwanted fibres.
AWI is investing more than $2 million over three years to 2007 to help protect Australia's reputation for high quality, clean white wool.
AWI's Dark and Medullated Fibre Program aims to:
- Quantify the global wool fibre contamination issue; and
- Develop a best practice system for on-farm risk assessment and routine pre-sale measurement of dark and medullated fibres.
Contamination problem
Contamination of the Australian Merino wool clip has traditionally been associated with dark fibres originating from urine stains and isolated pigmentation found in the fleece.
In recent years the introduction of fleece-shedding exotic sheep breeds has brought a new and increasing source of dark and medullated fibre contamination.
Dark and medullated fibres can be transferred into Merino wool by:
- Contact during mating;
- Contact with cross-bred offspring; or
- Accidental contact in paddocks or yards.
A single dark fibre in white or pastel-coloured fabrics can appear as:
- A thin dark line if it lies on the yarn's surface; or
- A dark smudge if it lies within the yarn structure.
A medullated fibre can become more visible as the colour of the fabric deepens.
Processors worldwide are expressing concern about wool fibre contamination.
A loss of Australia's reputation for high quality, clean white wool may lead to a reduction of price premiums for Australian wool over other wool producing countries.
Dark and medullated fibre contamination comes from 'exotic' meat sheep recently introduced to Australia.
These sheep can transfer fibres to Merino sheep:
- at mating when sheep producers are cross breeding for prime lamb production; and
- when ewes are rearing crossbred lambs.
Since the introduction of exotic sheep breeds to Australia, early and later stage wool processors across the globe have reported more dark and medullated fibres in Australian Merino wool tops.
This contamination costs about $100 million each year to remove or correct.
Single dark fibres in a white or pastel fabric after weaving need manual picking out - at a cost of more than 10 cents per kilogram - and there is potential risk of damaging the fabric.
Medullated fibres are hollow and contamination in Merino wool causes changes in the appearance of dyed fabrics, especially dark or black fabrics.
Declaration scheme
A voluntary Dark and Medullated Fibre Risk (DMFR) Scheme was introduced for Merino fleece and piece wool in July 2004.
It provides a rating of the risk of dark and medullated fibre contamination from contact between Merino and exotic sheep on Australian Wool Testing Authority (AWTA) test certificates and in sale catalogues.
The DMFR Scheme allows:
- wool producers to promote their clips as white and uncontaminated;
- wool buyers and processors to minimise the risk of buying contaminated wool;
- better analysis of price differences for wools with various contamination risks; and
- protection and advancement of Australia's woolclip reputation as white and non-contaminated.
Merino sheep producers have the option of supplying DMFR information for all, some or none of their fleece and piece lines.
Pre-sale measurement of dark and medullated fibres
AWI and CSIRO have developed a low cost, automated pre-sale test to more accurately quantify dark and medullated fibre contamination of Merino wool.
AWTA is working to commercially develop and trial this test.
The pre-sale test uses the core sample taken for routine pre-sale measurement of fibre diameter and yield.
It will assist the Australian wool industry maintain its enviable reputation for quality and low purchase risk.