An investigation into the aetiology of 'wool slip': alopecia in ewes which are housed and shorn in winter

Alopecia in housed ewes which are shorn in winter, 'wool slip', was investigated by taking wool and blood samples, skin scrapings and biopsies from affected and unaffected animals. Epidemiological information was also obtained from farm records, and reports from a local weather station. No pathological lesions were seen and no ectoparasites or forage mites were seen in wool samples or skin scrapings. The plasma zinc and copper concentrations of both groups were within the normal range but the copper concentrations were significantly lower in the unaffected animals. There was no difference between the prevalence of the disease in ewes of different breeds or between those producing single or twin lambs. A comparison of the mean temperatures during years of summer and winter shearing suggested that cold stress alone was not involved. Skin biopsies revealed that the wool follicles of affected animals were in an early growth phase (anagen) whereas those of unaffected animals were in the inactive phase (telogen). The clinical and histological signs of the disease were similar to those seen experimentally when corticosteroids are used as chemical depilatory agents. It is suggested that wool slip is due to the high levels of corticosteroids which occur as a result of the combination of housing and shearing and on this basis methods of control are proposed.