Effects of reduced crude protein diets on footpad dermatitis, necrotic enteritis, and coccidiosis in broiler chickens.

Reducing dietary crude protein (CP) with balanced amino acid (AA) supplementation has emerged as a practical nutritional strategy to improve the sustainability of broiler production by lowering nitrogen excretion, ammonia emission, and reliance on imported feed ingredients. Beyond these environmental and economic benefits, this review evaluates current evidence on how dietary crude protein levels influence key health and welfare outcomes, including footpad dermatitis (FPD), necrotic enteritis (NE), and coccidiosis in broiler chickens. The available literature indicates that moderate reductions in CP, when essential amino acid requirements are met, consistently reduce nitrogen excretion, litter moisture, litter pH, and ammonia release, thereby improving litter quality and reducing the incidence and severity of FPD and hock burn. While the relationship between reduced CP and NE is inconclusive, moderate CP reduction may alleviate NE-related damage by lowering the flow of undigested protein to the hindgut and reducing substrate availability for Clostridium perfringens, its causative agent. But excessive protein reduction and/or inadequate amino acid balance can impair performance and fail to protect gut integrity and increase the risk of NE. Responses are further complicated by concurrent changes in diet composition, particularly increased wheat inclusion and non-starch polysaccharide load, which may elevate digesta viscosity and favour pathogen proliferation when not adequately controlled with enzymes. In coccidiosis, reduced CP diets generally do not worsen outcomes when amino acid supply is correctly balanced, and targeted supplementation with functional amino acids such as arginine, threonine, and glutamine could support gut barrier integrity, immune responses, and recovery. Overall, the benefits of reduced CP feeding depend on the extent of protein reduction, amino acid adequacy, ingredient composition, and disease context. Precisely formulated reduced CP diets can contribute to improved welfare, gut health, and environmental sustainability in broiler production, but further work is needed to define the optimal crude protein and amino acid specifications under commercial disease-challenge conditions.