Residual feed intake in laying hens during the late laying period: associations with nutrient utilization, antioxidant capacity, and gut barrier function

Abstract Background Residual feed intake is defined as the difference between the actual feed intake of poultry and the predicted feed intake based on their growth and maintenance requirements. It reflects the metabolic differences that are genetically determined within the poultry and can effectively indicate the energy levels needed for growth and maintenance. Residual feed intake is a crucial indicator for evaluating the feed utilization efficiency of poultry. Additionally, residual feed intake is a trait with moderate to high heritability, making it a valuable selection criterion for feed efficiency in poultry breeding programs, and it is widely utilized in egg production. However, research on residual feed intake during the latter stages of egg production in hens remains quite limited. Results In this study, we selected laying hens with similar body weight and egg production number, and divided the experiment into low residual feed intake and high residual feed intake groups based on the magnitude of residual feed intake values. Through physicochemical analysis, compared to the high residual feed intake group, the low residual feed intake group exhibited higher nutrient utilization (crude protein, apparent digestibility of dry matter) and stronger antioxidant enzyme activity (T-AOC), as well as more stable gut immune barriers ( IL-6 ) and mechanical barriers ( Occludin , ZO-1 ). LC–MS revealed that the differentially abundant metabolites in the serum and excreta of the two groups were primarily enriched in amino acid metabolism, lipid metabolism, and energy metabolism pathways (L-lysine, L-glutamine, citrate, fumarate, propanoic acid, glycine, pyruvate.). These key differentially abundant metabolites provide new metabolic targets for a deeper understanding and improvement of feed efficiency in laying hens. Conclusion This study utilized traditional nutritional methods and modern molecular biology techniques to target the excreta, serum, and intestinal segments of hens with different RFI levels, providing an in-depth exploration of the metabolic differences between high- and low-RFI hens. The findings offer valuable insights for selecting high-efficiency, high-quality healthy laying hens through RFI. Furthermore, they support the extension of the laying period in hens and efficient breeding practices.