Quality of life framework in poultry: a methodological approach to characterize the behavior of chickens reared under free-range conditions

The “Quality of Life” (QOL) is a relatively recent approach to animal welfare that emphasizes animals’ subjective experiences and the need to ensure long-term positive affective states. In this study, the QOL framework was applied to poultry. Four slow-growing chicken genotypes (A, NN, CB, and LD) reared under free-range conditions were used as a case study to characterize behavioral patterns and gain insights into their welfare and adaptive capacity. Behaviors were monitored over extended observation periods (5 weeks) and classified as positive or negative affects; a quantitative indicator of their balance was then calculated (i.e., proportion of positive to total affects, PPA). The classification of behaviors, such as sheltering and attacking, proved to be challenging, necessitating a careful analysis of their functional significance, occurrence patterns, and distribution across the lifespan of the animal. The PPA index revealed that positive effects occurred more frequently than negative ones across all genotypes, ranging from 73.7 ± 4.8% in LD to 92.5 ± 3.6% in NN, without significant differences among genotypes. The study also highlighted that behavior classification should not be done a priori but rather depends on several factors, including occurrence and temporal dynamics, in addition to genotype and rearing conditions. Nonetheless, the QOL approach still presents challenges, and further research is required to refine the classification of behaviors into positive and negative affects and to develop robust indicators of their balance.