Effects of Replacing Soybean Meal with Different Proportions of Black Soldier Fly Larvae Meal on Antioxidant Indicators, Immune System, and Gut Health of Xichuan Black-Bone Chickens.

This study aimed to investigate the underlying mechanisms by which replacing soybean meal with different proportions of black soldier fly (BSF) larvae meal affects the antioxidant capacity, immune function, and intestinal health in Xichuan black-bone chickens. After feeding the diets with 0.0%, 3.9%, 7.8%, 11.7%, and 15.6% BSF powder for 56 days, twelve chickens were sampled from each group. The optimal addition group was determined. Compared with the control group, adding 11.7% BSF significantly increased serum T-AOC, SOD, IgA, IgM, IL-4, and IL-10 concentrations, while markedly reducing IL-1β, TNF-α, and IL-6 (p < 0.05) and improving spleen morphology. Adding 11.7% BSF significantly increased the duodenal villus-to-crypt ratio (V/C) and markedly elevated the ileal V/C (p < 0.05), and it significantly increased gene expression levels of duodenal Claudin-1, Occludin, and E-cadherin, jejunal Claudin-1, and ileal Claudin-1, Occludin, and E-cadherin (p < 0.05). Compared with the control group, the 11.7% addition group exhibited significant alterations in caecal microbiota composition (p < 0.05), with 10 distinct bacterial genera identified at the genus level. A total of 424 differentially expressed metabolites were identified. Correlation analyses revealed that adding 11.7% BSF may enhance immune function by regulating intestinal metabolites such as isovaleric acid, inosine, and tazarotenic acid via Akkermansia, Sphaerochaeta, and Blautia in the cecum. It may also improve gut health by modulating inosine through Sphaerochaeta and Blautia. This trial provides feasibility evidence for substituting soybean meal with BSF meal, offering scientific support for sustainable development in animal husbandry.