Mortality in commercial broiler flocks represents millions of animals dying each year, with causes including heart failure, ascites, leg weakness, and heat stress — all welfare-relevant.
Broiler mortality represents both a welfare failure and a signal of broader welfare problems in surviving birds. Birds dying of SDS and ascites have experienced cardiac and respiratory stress for some period before death. Lame birds dying because they cannot access resources have suffered prolonged pain and deprivation. Heat mortality events represent acute suffering preceding death. High mortality rates in a flock are welfare warning signs that require investigation and management response. Reducing mortality through breed reform, lower stocking density, and better environmental management simultaneously improves welfare for survivors.