Meat chicken breeder stress: causes, effects, and mitigation strategies

Abstract

<p>Meat chicken (broiler) breeders are exposed to many stressors, and arguably the most severe are feed restrictions during rearing and aggression during production. Chronic stress is a significant animal welfare concern and reduces productive performance in meat chicken breeders, including reduced egg production and hatchability. As such, minimising stress through effective management strategies is essential for the economic viability and sustainability of the chicken meat industry. This review evaluates approaches to reduce stress associated with hunger and aggression, including qualitative feeding programmes, appetite suppressants, and shed design. We highlight knowledge gaps that must be addressed before strategies can be implemented to reduce stress in breeders on commercial farms. Relaxing commercial feed restrictions could reduce hunger, improve welfare and boost productivity, and current feeding practices should be reassessed for modern breeder strains, focusing on behaviour and stress. Although slower-growing strains and certain feed additives can reduce hunger, they remain impractical due to the economic costs and potential welfare concerns, respectively. Qualitative feed restrictions, involving non-nutritive ingredients such as fibre, show promise in alleviating hunger-related stress. However, research is required to determine the optimal concentrations and composition to balance satiety, gut health, and water retention without causing other welfare problems like wet litter and dermatitis. Managing aggression-related stress currently relies on physical mutations, which are also problematic for welfare. Alternative strategies – such as adjusting sex ratios, synchronising sexual maturity and optimising lighting and shed design – offer potential solutions. Insights from rodent research suggest that building stress resilience through environmental complexity could also be effective. However, it is crucial to determine what environmental changes are both beneficial for the birds and feasible to implement in commercial conditions. We recommend a multidisciplinary approach to reducing stress in meat chickens, combining dietary fibre with strategies to enhance stress resilience, enabling birds to better cope with challenging situations.</p>