Adaptation to organic rearing system of eight different chicken genotypes: behaviour, welfare and performance

The aim of the study was to define poultry adaptability to organic system, through the assessment of several endpoints. Eight hundred male birds of slow-growing birds (Ancona: A, Leghorn: L, crossbreed Cornish x Leghorn: CL), medium-growing (Gaina: G, Robusta Maculata: RM, Kabir: K, Naked Neck: NN) and fast-growing strains (Ross: R) were organically reared. A and L genotypes displayed a quicker reaction time when submitted to tonic immobility test, and a great variety of behaviour and exploiting all the pasture area. Concerning feather conditions L, A, CL G and RM showed the best values for all considered body regions, as well as the absolute absence of foot pad and breast blister lesions. Static behaviour of R and G chickens did not produce a significant oxidative burst whereas, the active behaviour of A, slow-growing birds, increased the oxygen demand. Plasma alpha-tocopherol followed the trend of kinetic and foraging activity being higher in slow-, intermediate in medium-and lower in fast-growing birds. The adaptability index showed the best result of slow-growing strains with intermediate results in medium-growing and the worst in fast-growing ones. There is a negative linear correlation between adaptation and daily weight gain. However, within the same sub-group (slow, medium and fast), there is no correlation between daily weight gain and adaptation to an organic system. Even if R chickens had the highest productive performance, they appeared no adapted to the organic system. Daily weight gain (<50 g/d) is a prerequisite for chicken adaptation, but even birds with similar weight gains showed wide variations in the adaptation.