Effects of full-fat black soldier fly larvae (Hermetia illucens) meal on growth, gut health, and bone microstructure responses in broiler chickens.

The objective of this study was to evaluate the effects of graded replacement of soybean meal (SBM) with full-fat black soldier fly larvae (BSFL; Hermetia illucens) meal on growth performance, intestinal morphology, barrier and transporter gene expression, body composition, and femoral bone microstructure in broiler chickens. A total of 360 one-day-old male Cobb 500 broiler chicks were randomly assigned to 6 dietary treatments (n = 6 replicates/treatment, 10 birds/pen) in a 28-day feeding trial: T0 (0% BSFL), T2.5 (2.5%), T5 (5.0%), T7.5 (7.5%), T10 (10.0%), and T12.5 (12.5%) BSFL meal replacing SBM on an isonitrogenous and isocaloric basis, using pre-determined nitrogen-corrected true metabolizable energy (TMEn) and digestible amino acid values. BSFL inclusion did not affect feed intake throughout the trial (P > 0.05). However, birds fed 5% BSFL had the highest final body weight and body weight gain, with a significant quadratic response on day 28 (P < 0.05), whereas the 12.5% group had the lowest. Intestinal morphology followed the similar pattern where the 5% group had the highest villus height-to-crypt depth ratio in the duodenum (P < 0.05), indicating enhanced absorptive capacity at moderate inclusion. However, oxidative status was similar among the treatments with no statistical difference (P > 0.05). Similarly, TJP1 and TJP2 were significantly affected by treatment, whereas JAM-2 and Occludin showed downward linear trends with increasing BSFL inclusion, suggesting intestinal barrier compromise at higher inclusion levels. The large neutral amino acid transporter LAT1 was downregulated at 10-12.5% BSFL, whereas B⁰AT1, SGLT1, and y⁺LAT1 were unaffected. Body fat percentage increased linearly with BSFL inclusion (P < 0.001), and lean tissue percentage decreased correspondingly. Bone mineral density was preserved across all treatments while femoral trabecular microstructure parameters showed significant quadratic responses as BSFL inclusion increased (P < 0.05). In conclusion, replacing SBM with full-fat BSFL meal at 5% optimized broiler growth, intestinal integrity, and bone microstructure, whereas inclusion levels above 10% compromised gut barrier function.