# Effects of Black Soldier Fly (Hermetia illucens) Larvae Meal Replacement for Fish Meal on Growth Performance, Muscle Quality, Antioxidant Status, Immune Function, and Gut Microbiota in Juvenile Southern Catfish (Silurus meridionalis)

## TL;DR

This study shows that replacing fish meal with black soldier fly larvae meal in the diet of southern catfish improves growth and health markers, making it a promising sustainable alternative.

## Contribution

The study demonstrates that 50% replacement of fish meal with black soldier fly larvae meal optimizes growth and health in southern catfish.

## Key findings

- A 50% replacement of fish meal with black soldier fly larvae meal significantly improved weight gain, growth rate, and protein efficiency in southern catfish.
- Gut microbiota shifted with increased Clostridia and Escherichia at higher substitution levels, suggesting microbial cooperation through metabolite exchange.
- Muscle texture properties were altered, but muscle amino acid and fatty acid profiles remained unchanged with BSFLM substitution.

## Abstract

This study evaluated the effects of feeding juvenile southern catfish (Silurus meridionalis) with one of six isonitrogenous and isoenergetic diets where fish meal (FM) was replaced by black soldier fly larval meal (BSFLM) at 0%, 10%, 20%, 30%, 40%, and 50% levels on growth, muscle quality, antioxidant capacity, immune response, and gut microbiota of juvenile southern catfish (Silurus meridionalis). A total of 1620 fish (9.20 ± 0.15 g) were fed one of six experimental diets for 8 weeks. Results demonstrated that a 50% replacement (H50 group) significantly improved weight gain rate, specific growth rate, and protein efficiency ratio (p < 0.001). Antioxidant capacity (T-AOC) was enhanced in groups H30 and H50, while immune markers lysozyme (LZM) and alkaline phosphatase (AKP) showed mixed responses. Muscle texture properties such as chewiness and adhesiveness were significantly altered across treatments. Gut villi remained structurally intact in all groups, and liver histology appeared normal. No significant differences were found in muscle amino acid or fatty acid profiles. Gut microbiota analysis revealed shifts in microbial composition, with increased abundance of Clostridia and Escherichia and functional enrichment in metabolic pathways at higher substitution levels. Interspecies network analysis indicated potential cooperation among beneficial microbes through metabolite exchange. It is concluded that 50% BSFLM substitution optimizes growth performance, muscle quality, and antioxidant capacity, while modulating gut microbiota, indicating its promise as a sustainable FM alternative and functional ingredient in aquafeeds.