Research Note: Black soldier fly larvae oil restores intestinal barrier integrity and attenuates inflammation in broiler chickens fed low crude protein diets.

Feeding low crude protein (LCP) diets supplemented with crystalline amino acids provides benefits for production, environmental sustainability, and animal welfare. However, LCP diets can adversely affect intestinal growth and barrier function in broiler chickens. Black soldier fly larvae oil (BSFLO), containing high lauric acid, has potential for improving gut health. A 3 × 2 factorial design was conducted to investigate the effects of BSFLO supplementation on jejunum morphology, barrier integrity, and inflammatory responses in broiler chickens fed LCP diets. A total of 288 broilers were divided into 6 treatments: based on three levels of crude protein (CP): (200, 185, or 170 g/kg; high [HCP], medium [MCP] or low [LCP]) and two oil sources (BSFLO and crude palm oil; CPO), with 6 replicates and 8 birds each. Results showed that reducing CP levels significantly decreased villus height (VH; P = 0.001) but had no effect on villus width (VW), crypt depth (CD), and VH:CD ratio (P>0.050). Oil supplementation had no significant impact on jejunum histomorphology parameters (P>0.050). The expression of tight junction-related genes (CLDN-1, JAM-2, and ZO-1) was significantly downregulated (P<0.001) in broilers fed LCP diets, particularly at a CP level of 170 g/kg. However, supplementation with BSFLO significantly upregulated (P < 0.001) the expression of tight junction-related genes (JAM-2 and ZO-1) despite CP reduction. Moreover, dietary LCP diets increased (P < 0.001) the expression of pro-inflammatory genes (IL-6, IL-18, and TNF-α) and decreased (P = 0.033) the expression of the anti-inflammatory gene (IL-13). Notably, BSFLO supplementation mitigated (P < 0.001) the upregulation of pro-inflammatory gene expression (IL-6 and IL-18) and significantly increased the expression of anti-inflammatory genes (IL-13). This study demonstrates that BSFLO improved gut barrier integrity in broiler chickens fed LCP diets by upregulating the expression of tight junction-related genes (JAM-2 and ZO-1) and anti-inflammatory cytokines (IL-13), while downregulating pro-inflammatory cytokines (IL-6 and IL-18).