ORCID
- Sahya Maulu: 0000-0003-4402-623X
Abstract
Three experimental trials were conducted to evaluate defatted black soldier fly (BSF; Hermetia illucens) larvae meal and BSF frass as alternative protein ingredients. Defatted BSF larvae meal was tested in diets for both Nile tilapia (Oreochromis niloticus) and mirror carp (Cyprinus carpio), whereas BSF frass was assessed only in Nile tilapia.In the first experiment, dietary inclusion of 20% and 40% BSF meal, replacing mainly soybean meal (SBM) and corn gluten meal (CGM), was evaluated in Nile tilapia over 5 weeks. BSF improved growth and feed utilisation in a dose-dependent manner, increased posterior intestinal fold length, muscularis thickness, and goblet cell density, while intraepithelial lymphocytes abundance and enterocyte microvilli length were elevated only at 40% BSF meal. Posterior intestinal endochitinase A, slc6a18, and cytokines (il1β, tnfα, il10) in either the intestine or head kidney were not significantly affected, but slc15a1a was upregulated at 40% BSF meal compared with the control.Similar results were obtained in juvenile mirror carp fed the same BSF meal at 20% and 40% over 8 weeks, replacing mainly SBM and soy protein concentrate (SPC). 16S rRNA gene metabarcoding profiling of the posterior intestine revealed that BSF inclusion induced beneficial microbiome changes. BSF meal significantly increased the relative abundance of Firmicutes and reduced a number of potentially pathogenic phyla. At the genus level, BSF meal enriched the relative abundances of beneficial Bacillus and Enterococcus while reducing potentially pathogenic Mycobacterium, Staphylococcus, and Enterobacter. In the third experiment, 30% BSF frass inclusion was evaluated on growth, intestinal health, immune responses, and intestinal microbiota in Nile tilapia over 6 weeks. Results revealed that BSF frass significantly increased posterior intestine enterocyte microvilli length and density without affecting overall tissue morphology. Expressions of posterior intestinal cytokines (il1β, tnfα, il10, tgfβ), tight junction proteins (cldn3, ocln), and mucosal immunity markers (IgM, pIgR, muc2) were unaffected, while β-defensin 1, pcna, and hsp70 were downregulated. While microbiota diversity remained stable across the diets, BSF frass reduced Proteobacteria and Campylobacterota, and increased Spirochaetota and Brevinema. Growth performance and carcass composition did not differ significantly between the groups. These trials demonstrate that incorporating defatted BSF larvae meal at 20% and 40% inclusion rates is a viable alternative to plant-based proteins in diets for Nile tilapia and mirror carp, and that including BSF frass at 30% is a feasible option for Nile tilapia diets. Both ingredients provide nutritional and functional benefits in these species.
Awarding Institution(s)
University of Plymouth
Supervisor
Daniel Merrifield, Mark Rawling
Document Type
Thesis
Publication Date
2026
Embargo Period
2026-02-10
Deposit Date
February 2026
Additional Links
Creative Commons License
This work is licensed under a Creative Commons Attribution-NonCommercial 4.0 International License
Recommended Citation
Maulu, S. (2026) Investigating the potential utilisation of black soldier fly (Hermetia illucens) as an alternative protein source in tilapia and carp feed. Thesis. University of Plymouth. Available at: https://doi.org/10.24382/svbk-gf62
