Effect of Black Soldier Fly Larvae Meal (Hermetia illucens) and Microbial Probiotics with Multi-enzymes on Protein Efficiency Ratio, Metabolic Profile, and Immune Status of Broiler Chickens

Black soldier fly larvae meal (BSFLM; Hermetia illucens) has been authorized in the EU as an insect-derived protein for feed and is a promising alternative to soybean meal (SBM), with potential functional benefits attributed to lauric acid (LA), chitin, and bioactive peptides; however, evidence is limited regarding its interaction with probiotic–multi-enzyme complexes. Thus, we investigated whether replacing SBM with BSFLM, with or without a microbial probiotic and multi-enzyme blend (MPE). A total of 225 one-day-old Ross 308 chicks were allocated to nine treatments in a 3× 3 factorial design (five replicates of five chicks) from 1–38 d, using mash diets in which SBM was replaced by 0, 25, or 50% Black soldier fly larvae meal (BSFLMP) which represented 0, 11.4, 21.9% BSFLMP in starter-grower; 0, 8.8, 17.4% BSFLMP in finisher) and supplemented with 0, 0.5, or 1.0 g/kg MPE. BSFLM ether extract was high (24.7% DM) and dominated by LA (43.04% of fatty acids) and oleic acids (10.48%). The highest PER was observed with 25% BSFLMP plus 0.5 g/kg MPE (PER 3.23). BSFLM (particularly 50%) enhanced lymphoid organ indices, and increased antioxidant/immune markers (higher total antioxidant capacity (TAC), glutathione peroxides (GS-Px), immunoglobulin-G (IgG)/immunoglobulin-M (IgM); immunoglobulin-A (IgA) increased with 50% BSFLM) without adverse effects on alanine-aminotransferases (ALT)/ aspartate-aminotransferases (AST) or creatinine (Cre)/urea ratio, although alkaline phosphatase (ALP) increased with 50% BSFLM. Overall, partial SBM replacement with 25% BSFLM, optimally at 0.5 g/kg MPE, is recommended to improve protein utilization, oxidative status, and immunity while maintaining metabolic health.