Contact dermatitis in domestic poultry.

Abstract Contact dermatitis is a common finding in commercial poultry kept for meat production that has both economic and welfare implications. The disease commonly affects the epidermis of the foot pad, hock joint and skin covering the breast muscles that are in contact with the litter or other floor materials. Welfare legislation in Europe has been implemented that requires farmers to reduce stocking rates if broiler chickens presented at the abattoir have a certain prevalence of foot pad dermatitis (FPD) as a proxy for poor welfare during the rearing. It has long been known that birds kept in deep litter systems are affected by foot pad dermatitis and hock burns if the litter contains too much water. The moisture content of the litter is affected by many factors (e.g. litter substrate, humidity, air temperature, stocking rate and gut health). Recently it was shown that adding water to clean wood shavings was sufficient to induce FPD and that the prevalence and severity of disease increased linearly above a certain minimum water content. The role of excess minerals, particularly sodium, and high electrolyte balance have been associated with increasing litter moisture and contact dermatitis. Hock burns and breast burns have a similar aetiology as FPD and have also been linked with high litter ammonia. Breast buttons (focal ulcerative dermatitis) and breast blisters (sternal bursitis) may be associated with poor breast feathering that exposes the naked skin to the litter. FPD, hock burns and focal ulcerative dermatitis have a similar aetiology whereas sternal bursitis is probably related to friction. FPD is associated with a cytokine milieu that is consistent with an inflammatory reaction but the precise stimulus for this response is not known with certainty. FPD has also been reported in laying hens and broiler breeders and is more prevalent in non-cage systems and in birds with outdoor access. Research indicates that optimum dietary concentrations of vitamins and minerals are necessary to maximize skin health and that management practices must be employed to create dry, friable litter in order to minimize contact dermatitis.