Response in Sheep to Shearing
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Farmers worry about the stress caused by certain management practices. Will production be affected? Could these practices make my sheep more susceptible to disease? In the last few years researchers in Lethbridge, Alberta believe they have found a way to evaluate the intensity of stress caused by management practices. Animals under stress put out certain hormones that can be measured in the blood. Researchers, Mears and Brown, measure the blood levels of hormones, cortisol and beta-endorphin. These investigators use hormone release changes to relate to the level of stress. Previously they found weaning and restraint to be moderate stressors for lambs. These same researchers have measured the effects of handling and shearing on ewes.
Ewes were broken into two groups, those who had never been sheared before - naïve ewes - and those who had been sheared one to four times on an annual basis. The objectives were to separate the effects of shearing from those of normal handling procedures during shearing and to determine if the experienced ewes' hormonal systems adapted to shearing. In each of the two groups some animals were exposed to simulated shearing or "sham-shearing". The shears were moved around the sham-sheared ewes to simulate shearing but the shears never actually touched the ewes.
There was not a difference in blood levels for the two hormones between the sham-sheared ewes and the sheared ewes. Researchers concluded shearing did not stress ewes beyond the stress caused by the handling procedures.
Researchers did not expect to find previously sheared ewes to be stressed to a much greater extent than naïve ewes. However, hormone levels went higher in experienced ewes shortly after they were exposed to the sounds, smells and sights of the shearing room. These hormones also lasted longer in the blood of the experienced ewes. Observers felt the experienced ewes appeared less upset during handling and shearing compared to naïve ewes. The conclusion was exposure to an unpleasant handling practice may have an adverse effect on sheep at a much later date. The ewes negatively adapted to the shearing process. They remember. Well designed handling and shearing facilities can reduce the stress on ewes. Experienced shearers and handlers can make for less stressful memories for you and your sheep.
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