Carbohydrate and protein adaptation in low-protein diets for livestock and poultry: a nutritional revolution from static balance to dynamic synergy.

Low-protein diet is a pivotal strategy for alleviating protein feed shortage and promoting the sustainable development of the livestock industry. However, the utilization efficiency of carbohydrate and protein nutrients in livestock and poultry remains relatively low, and carbohydrate-protein metabolism asynchrony is the core bottleneck limiting their efficient utilization. Carbohydrate and protein adaptation, based on low-protein diets, makes a shift from traditional static energy and nitrogen balance theories. By precisely aligning the digestive release patterns of carbohydrates and proteins, it enables the synergistic and efficient utilization of energy and amino acids, representing a promising concept in the low-protein diet systems. Nevertheless, current evidence supporting carbohydrate and protein adaptation remains relatively limited and largely based on indirect inference. This review summarizes the patterns of digestion and absorption of carbohydrate and protein in livestock and poultry as well as their key regulatory factors, clarifies the core technology and cutting-edge research methodologies for carbohydrate and protein adaptation, and analyzes the mechanisms by which carbohydrate and protein adaptation influences production performance, meat quality, intestinal health, and nutritional metabolism regulation. In addition, this review proposes future research directions, including quantitative and precise regulation, microbiome-targeted modulation, and multi-omics mechanism analysis, providing a theoretical basis for further research and industrial application of carbohydrate and protein adaptation in low-protein diets for livestock and poultry.