The genetics of contact dermatitis in poultry.

Abstract

Abstract The prevalence of contact dermatitis traits is an important consideration in modern poultry production, as part of the general focus on leg health and welfare traits. Contact dermatitis is seen as a lesion or discolouration of the skin, potentially accompanied by inflammation or necrosis. Various scoring systems have been developed, often relating ordinal scores to the proportional area affected. Environmental factors have a significant effect on its prevalence, but studies have shown that genetic variation exists for foot pad dermatitis (FPD) in chickens and turkeys and for hock burn in chickens. This review shows genetic parameters for contact dermatitis traits in contemporary chicken and turkey populations in the Aviagen breeding programmes, and their genetic correlations with production traits. FPD is recorded in all Aviagen breeding programmes, with hock burn additionally recorded in the Aviagen chicken breeding programmes. All traits are scored at commercially relevant ages on a four or five point scale (depending on trait/species) through visual inspection by a trained team of scorers. Heritabilities for FPD in chickens range from 21% to 32% and for hock burn from 9% to 23%. Genetic correlations with body weight are generally favourable (FPD) or moderately unfavourable (hock burn). Heritabilities for FPD in turkeys range from 5% to 16%, with low to moderately unfavourable genetic correlations with body weight. Genetic selection to improve contact dermatitis has been incorporated effectively for chickens and turkeys in commercial breeding programmes. The differences in heritability for FPD between the species may be due to fundamental differences of the expression of contact dermatitis, despite similar phenotypes. However, in both species genetic correlations with a production trait were only low to moderately unfavourable or even favourable. In broad breeding goals, where the focus lies simultaneously on welfare traits and production traits, progress can be achieved simultaneously despite potentially antagonistic correlations.