“Cortisol is the fight-or-flight hormone, giving you the burst of energy needed to be able to remove danger, or yourself from danger,” says Dr Melanie McDowall of the School of Animal and Veterinary Sciences.
Merino ewes were treated with the anti-cortisol drug metyrapone for 10 days at the time when their wool follicles are developing. “Right from birth the lamb coats could be distinguished visually,” McDowall says. “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.” Moreover, in the first 3 years the lambs continued to produce fibres that were 10% longer.
While the effect on wool was obvious, the lambs were indistinguishable in other ways, notably in weight at birth and shearing.
McDowall says it would be difficult to achieve the same cortisol-lowering effects by removing stressors in the environment since “sheep are by their nature fairly flighty. Breeders do try to select for those with manageable temperament, but selective breeding is a slow process.”
Metyrapone is an expensive chemical, and McDowall says that “this trial cost thousands of dollars”. Consequently, “for a producer to administer metyrapone to pregnant ewes would be uneconomical”. However the research, published in Animal Production...
