Way forward for woollier sheep: study RESTRICTING the stress hormone cortisol in pregnant ewes can lead to sheep that produce more wool, a new study has found. Researchers at the University of Adelaide produced lambs that were hairier at birth and produced 10 per cent longer wool fibres over the first three years. Lead researcher Melanie McDowall says the results indicate it's possible to alter lifetime wool production of merino sheep by manipulating cortisol levels in pregnant ewes at key times. "This very quick result to improve yield can be compared to selective breeding which would take many years to see such an extreme improvement in production," Dr McDowall said in a statement on Tuesday. As part of the study, pregnant merino ewes were treated for 10 days with a cortisol-inhibiting drug metyrapone at a critical time for wool follicle development in the lamb fetus. Another group of ewes was given a cortisol-like substance and both groups were compared with a control group of pregnant ewes that weren't treated with either drug. "Right from birth, the lamb coats could be distinguished visually," Dr McDowall said. Those with higher cortisol levels had tighter, shorter and curlier fleeces. Those with reduced cortisol looked a little like golden retriever puppies, their coats were longer and shaggier. Dr McDowall said while it would be uneconomical for producers to administer metyrapone to pregnant ewes it was possible further research could lead to more targeted gene therapy.