Amino-Acid-Balanced Low-Protein Diets Reduce Nitrogen Excretion Without Affecting Growth Performance in Broilers

Reducing greenhouse gas emissions from the livestock industry is essential for climate change mitigation. In poultry production, nitrous oxide (N2O) emissions from composted manure are a major concern because they are closely associated with nitrogen content in the manure. This study investigated whether feeding broilers amino-acid-balanced low-crude-protein (AALP) diets throughout the entire rearing period could reduce nitrogen excretion without affecting growth performance. Thirty-six male broiler chicks were assigned to a control diet or an AALP diet, and nitrogen excretion was estimated over 50 days using chromic oxide as an indigestible marker. Overall growth performance was maintained in the AALP group, with a significant improvement in feed conversion ratio during the grower phase. Organ weights were largely unaffected, although liver weight tended to increase. Nitrogen excretion was significantly reduced at most time points in the AALP group, with a cumulative reduction of 31.1% compared to the control, as estimated by model-based integration over days 7–47. These findings suggest that our designed AALP diets can effectively reduce nitrogen excretion while maintaining productivity, thereby contributing to sustainable poultry production and supporting national climate goals.