There has been increasing advocacy and consumer pressure on primary breeders, producers, processors and retailers to improve the welfare of the billions of chickens processed annually. Several small-scale studies have reported better welfare outcomes for slower growing strains compared to fast growing, conventional strains. However, these studies often housed birds with range access or used strains with vastly different growth rates. Additionally, there may be traits other than growth, such as body conformation, that affect welfare.

As the global poultry industry considers the implications of using slower strains, there was a need for a comprehensive, multidisciplinary examination of broiler chickens with a wide range of genotypes differing in growth rate and other phenotypic traits. The scientific team at University of Guelph, including expertise in animal welfare science, poultry nutrition, meat science, immunology, physiology, phenomics and biostatistics, designed this study to benchmark data on conventional and slower growing strains of broiler chickens reared under identical conditions. 

Scientists studied over 7,500 broiler chickens from 16 different genetic strains over a two-year period with the objective to understand differences in behaviour, mobility, anatomy, physiology, mortality, feed efficiency and carcass and meat quality as they relate to the strains’ growth rates. Strains were categorized by growth rate (as conventional (CONV), fastest slow strains (FAST), moderate slow strains (MOD) and slowest slow strains (SLOW)) to facilitate decision makers in their policy development, breeding goals or purchasing decisions based on animal welfare, production, efficiency and product quality.