Nitrogen utilization efficiency in dairy cattle is improved by nutritional, genetic, and management strategies

Abstract Nitrogen utilization efficiency (NUE) is a key factor in improving dairy farm profitability and reducing environmental nitrogen losses. However, evidence on nutritional, genetic, and management strategies remains fragmented across disciplines. Following PRISMA 2020 guidelines, this systematic review synthesized evidence from 115 eligible studies identified from 1,215 records to evaluate approaches for improving NUE in dairy cattle. Nutritional strategies provided the most consistent improvements; reducing dietary crude protein (CP) from approximately 17–19% to 15–16% generally decreased urinary nitrogen losses while maintaining milk production when amino acid supply was balanced. Genetic selection offers a long-term opportunity to improve NUE, although progress is constrained by low-to-moderate heritability (h 2 = 0.06–0.20) and genotype-by-environment interactions. Precision management approaches, including targeted supplementation, automated feeding, and real-time monitoring, further enhanced nitrogen utilization. Overall, improving NUE requires an integrated strategy that combines balanced protein nutrition, amino acid optimization, genetic improvement, and precision management. Future research should focus on standardized NUE measurement methods and long-term whole-farm evaluations of environmental and economic outcomes.