Dynamics of enzyme and metabolic profile of broilers fed black soldier fly (Hermetiailucens) larvae-based diets

This study investigated the impact of replacing fishmeal with black soldier fly larvae meal (BSFLM) on growth performance, microbial enzyme activity, and metabolic functions in broiler chickens. A total of fifty Arbor Acre Plus chicks were distributed across five dietary groups, including a control (100% fishmeal) and four diets containing increasing levels of BSFLM (25%, 50%, 75%, and 100%) in a completely randomized design. Broilers were reared over eight weeks, and cecal samples were subjected to 16S rRNA metagenomic sequencing to profile gut microbial enzyme activities and metabolic functions. Results revealed a progressive increase in microbial enzyme abundance and functional metabolic pathways with higher BSFLM inclusion, particularly in the 50% (T3) and 100% (T5) groups. Key enzymes, including ABC-2-type ATP-binding proteins, RNA polymerase sigma factors, and carbohydrate-active enzymes, were significantly upregulated, supporting enhanced carbohydrate fermentation, amino acid biosynthesis, and central carbon metabolism. Metabolic pathway analysis indicated a dietary shift from carbohydrate-driven fermentation in the control group to a more protein- and lipid-centered metabolism in BSFL-fed birds, with T3 showing a balanced metabolic profile and T5 exhibiting hyper-metabolic activity. These findings demonstrate that BSFLM can replace fishmeal without compromising gut health and may even enhance microbial functionality, with a 50% replacement emerging as an optimal inclusion level to sustain balanced microbial metabolism.