The health of broiler chicken gut microbiomes is fundamentally linked to litter quality, housing environment, and antibiotic use — with gut dysbiosis causing welfare harms including necrotic enteritis and impaired immunity.
Broiler gut health represents a nexus of welfare, antibiotic resistance, and environmental concerns that are increasingly recognised as inseparable. Gut dysbiosis in broiler flocks causes welfare harm through intestinal inflammation, reduced nutrient absorption, impaired immune function, and the painful, debilitating course of necrotic enteritis. Subclinical gut dysfunction — below the threshold of clinical disease — nonetheless impairs welfare through reduced growth efficiency and increased susceptibility to other health challenges. The historical use of sub-therapeutic antibiotics to maintain gut health has created antibiotic-resistant pathogen populations with serious public health implications, leading to regulatory restrictions in many countries. The welfare challenge now is to manage gut health effectively without routine antibiotic use — requiring improved litter management, vaccination against coccidiosis, dietary modification, and the development of validated probiotic approaches.