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Wrinkly Sheep A Worry

Dr David Scobie

Since the 1920s, it's been recognised overseas that wrinkly pelts on sheep mean lost earnings and greater costs, but recent research by AgResearch has thrown up a new wrinkle.

AgResearch has been studying Merino and mid-micron sheep and the value of their meat, wool and pelt. A plain-bodied ewe returns about $7 per head more than a wrinkly ewe from wool, meat and pelts. A wrinkly ram could easily cost a New Zealand sheep producing business $100 in lost earnings in the first year alone, then there are the on-going penalties and greater cost of flystrike control and labour inherited by his progeny.

Wrinkly rams and ewes produce wrinkly lambs, and these produce ribby pelts. Both rams and ewes that have wrinkles have 10% lower fertility. Wrinkly sheep wean 10% fewer of the lambs born and the wrinkly lambs grow much more slowly.

In Merinos, the most economically important trait is wool fibre diameter. Plain-bodied adult Merino ewes tend to produce finer wool (0.5 microns). This is partly a consequence of raising more lambs.

Wrinkly sheep do produce more greasy wool, but much of the extra weight is grease. Fibre diameter is greater on the wrinkles, which leads to greater variation in diameter in the fleece and potentially increasing the "prickle factor" in the end-products.

Wrinkly sheep produce shorter staples. The length of those staples is also more variable because staples on the wrinkles grow more slowly than on the skin between the wrinkles. Wrinkly sheep produce more second cuts because it is impossible for the shearer to harvest all the staples at an even level when they keep running into "speed bumps."

All this has been known for some time and, since the 1920s, farmers in Australia, South Africa and America have selected against wrinkly sheep. The AgResearch research in New Zealand has shown that wrinkly sheep are also far more susceptible to flystrike, and that their death rate is greater at any age.

Wrinkly sheep take up to a minute longer to shear. They are also slower to crutch and crutching is less effective at controlling flystrike in wrinkly sheep. The fleeces of wrinkly sheep tend to yellow more during processing and storage, because of the greater grease content. Pesticide residues are also retained more in the greasier wool.

The earliest opportunity to see wrinkles is when the lambs are born and their wool is short. The wrinkles are usually still readily visible at docking, and the worst animals should be marked as a cull at this time. Culling the very wrinkly ewes from the flock is an easy process following shearing. They carry more shearing cuts and the worst wrinkles are clearly visible.

Dr David Scobie is with AgResearch Lincoln.