Selective sheep breeding could lead to chemical-free shrink-proofing

Woollen jumpers may soon be shrink-proof without the use of chemicals, thanks to the finding that wool shrinkage (felting) is a heritable trait that can be manipulated through selective sheep breeding.

A collaborative project between CSIRO Livestock Industries, which performed the wool measurements, and the WA Department of Agriculture, which provided the pedigree flock, indicates that clothing, yarns and fabrics made from low felting wool tend to have reduced shrinkage and pilling compared to fabric produced from high felting wool. Low-felting wool also produces longer length and less entanglement during the cleaning process, resulting in fewer breakages during spinning.

Felting occurs due to realignment of wool fibres during processing. This realignment occurs because the fibres have a rough edge of 'saw teeth' that catch on each other, pulling the strands closer together and causing shrinkage. This is an advantage when producing felted products -- which make up about five per cent of the wool market in Australia -- but causes significant problems in the manufacture of knitted and woven wool products.

Non-shrink woollen products are currently produced using chemical treatments during processing (such as chlorination and coating with resin) which puts a layer on the fibres effectively preventing them from catching on each other. Other processes lock the fibres together so they cannot move. Although successful, these techniques are environmentally unfriendly, expensive and damage the fibres.

In collaboration with WA Department of Agriculture geneticist Dr Johan Greeff, CSIRO Livestock Industries' Dr Tony Schlink processed more than 2000 wool samples from the Katanning Merino resource flocks for various wool fibre traits and 'feltball density'.

There is a relationship between the thickness of a fibre and felting -- the finer the fibre gets the more it felts. Wool also has a natural wave in it and there is a relationship between this wave pattern and felting as well. Using pedigree information and removing the effects of fibre diameter, fibre curvature and yield, the wool's heritability for felting was assessed.

"The thickness of the fibre and the waviness have economic value so people want to select sheep for these characteristics as well, so we had to know if we could achieve felting independently of these characteristics, and we can," said Schlink. "So you can still have a fine fibre and a curvy fibre plus you can breed for a felting characteristic. That means there is a genetic combination in the sheep that is purely aimed at the felting characteristic.

"We know we can breed this type of animal, now it's a question for the industry to answer about whether these animals are worth it. In reality, particularly for felting, you need a label on a product saying this is where this wool comes from."

Some European companies use enzymic processes to shrink-proof wool and market it with a 'clean green' label. Perhaps these labels will soon appear on Australian jumpers.