Synergies and Trade-Offs in Modern Poultry Nutrition: An Integrated Framework Linking Animal Health, Productivity and Greenhouse Gas Mitigation.

Poultry nutrition simultaneously affects animal health, productive efficiency, product quality and the environmental burdens associated with feed production and manure management. Nutritional interventions may generate synergies among these outcomes, but they can also shift costs or environmental impacts across biological and supply-chain boundaries. This review critically evaluates low-protein diets, functional additives, feed enzymes, alternative protein sources, precision-feeding technologies and nutritional approaches to manure-emission mitigation. The evidence indicates that improved intestinal function and nutrient retention can reduce feed requirements and nutrient excretion, whereas excessive protein restriction, unstable additive responses, limited alternative-ingredient supply and poorly validated digital systems may compromise performance, product quality or economic feasibility. Environmental benefits are also sensitive to ingredient origin, processing, transport, crystalline amino acid and additive manufacture, coproduct allocation and life cycle assessment assumptions. To integrate these considerations, we propose a four-level conceptual decision framework comprising physiological adequacy, precision nutrient supply, constraint-specific functional intervention and whole-chain verification. The framework treats health, productive performance, product quality, economic feasibility and environmental impact as simultaneous decision criteria, while genotype, production stage, disease pressure, climate, ingredient availability and market objectives define the conditions of application. Standardized life cycle assessment and commercial validation are required to distinguish reproducible net benefits from improvements confined to individual indicators. This approach provides a structured basis for selecting poultry nutritional strategies that remain biologically effective, economically accessible and environmentally beneficial under practical production conditions.