The Dark and Medullated Fibre Risk (DMFR) Scheme, allows woolgrowers to accurately asses the risk of contamination.

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 invests  in the Dark & Medullated fibre program to help protect Australia's reputation for high quality, clean white wool.

This program aims to:

• Quantify the global wool fibre contamination issue
• 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.

Figure 1. Sources of dark fibre contamination: urine-stain and pigmentation (Source: www.tft.csiro.au)

Dark and medullated fibre contamination comes from 'exotic' meat sheep recently introduced to Australia.  Dark and medullated fibres can be transferred into Merino wool by:

• Contact during mating
• Contact with cross-bred offspring
• 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
• 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 express concern about wool fibre contamination.

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.

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.

The DMFR scheme is primarily based on the CSIRO’s dark fibre risk tree with additional information included on the contamination risk posed by contact with exotic breeds. The scheme has a scale from 1 to 6.Risk Levels 1 and 2 being most suitable for sensitive end-uses.

The objective information required for the calculation of the DMFR for Merinos includes wool types and description, sex, age, crutching, crutch/shear interval and mated to, reared or run with exotic sheep (or their crosses). The information is collected on the Classer’s Specification or separate declaration form and the DMFR calculated at a central computer. Endorsed by IWTO and AWEX, the DMFR Factor is reported on test certificates and in sale catalogues.

The declaration provides white wool producers with the opportunity to identify their product as such; while buyers/processors have objective data on the potential contamination risk.

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.