Preliminary investigations into the etiology and treatment of cockle, a sheep pelt defect

A defect of sheep pelts known as cockle, detectable after depilation, but usually first noted only in the pickled pelt or tanned stage of processing, was studied to establish causal factor(s) and effective treatments. In addition, data on the histology and seasonal prevalence of the disease were obtained. Samples collected soon after slaughter from pelts identified at the pickled pelt stage as having cackle, had a superficial dermatitis with infiltration of eosinophils. This may represent an immediate hypersensitivity reaction of the sheep to lice. Treatments of sheep with either insecticides, disinfectants or shearing showed that where biting lice (Bovicola avis) were removed, cackle lesions had either disappeared or regressed on pickled pelts. In Trial 1 diazinon reduced cackle prevalence and severity substantially; cypermethrin had a less pronounced effect. In Trial 2 diazinon, cypermethrin, Hibitane(R) and Savlon(R) were equally effective in reducing biting louse numbers as shown by counts oflice at 35 and 63 days post- treatment. Reduction of cockle on pelts from sheep slaughtered at 39 days post-treatment was achieved best by both diazinon and shearing. Examination of other pelts at 67 days post- treatment showed diazinon and Hibitane to be equally effective in reducing cackle. Furthermore, shearing in the absence of insecticides reduced the severity and extent of lesions on cackled pelts. The diazinon excipient and zinc sulphate were consistently poor at removing lice and reducing cackle prevalence and severity. The results have important implications for the leather industry in that shearing and good dipping practice with appropriate chemicals at the right time can lead to improved pelt quality. However, an incentive scheme for farmers, and a means of identifying individual pelts to the farms or origin, are both necessary before a marked improvement is likely to occur.-