Frass from black soldier fly larvae, Hermetia illucens, as a possible functional dietary ingredient on channel catfish feed

Authors: Aksoy, Mediha; Eljack, Rashida; AKSOY, JANSET - Auburn University; Beck, Benjamin

Submitted to: Fishes
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/31/2023
Publication Date: 11/2/2023
Citation: Aksoy, M., Eljack, R.M., Aksoy, J., Beck, B.H. 2023. Frass from black soldier fly larvae, Hermetia illucens, as a possible functional dietary ingredient on channel catfish feed. Fishes. 8(11):542. https://doi.org/10.3390/fishes8110542.
DOI: https://doi.org/10.3390/fishes8110542

Interpretive Summary: In the recent years, insect meal has received wide attention as a potential source of protein alternative to fish meal to use in aquaculture. We recently demonstrated that larvae frass from black soldier fly byproduct has a specific growth promoting effect on channel catfish increasing feed intake. Frass has the potential for use as a source of protein or as an ingredient for enhancing palatability of the diet of channel catfish. Moreover, frass contains immunostimulatory compounds such as antimicrobial peptides, lauric acid, chitin, and beneficial microbes. The present study was performed to evaluate the changes in hematology, serum chemistry, immune responses and disease resistance of channel catfish fed diets containing frass from black soldier fly larvae. Five diets containing frass at levels of 0, 5, 10, 20, and 30% as partial replacements of a combination of soybean meal, wheat short and corn meal on an equal protein basis were fed to juvenile catfish to apparent satiation twice a day for 10 weeks. Hematological parameters -red blood cell count, hemoglobin, and hematocrit- were significantly higher in fish fed 10% or higher dietary frass. Serum biochemistry of fish was not affected by dietary treatment. Fish on the diets containing frass at levels 20% or more showed significantly higher survival than that of control fish or fish on lower levels of dietary frass. Dietary inclusion of larval frass, particularly at higher levels, appears to be beneficial in improving hematological and immunological indexes and increasing resistance of channel catfish to F. covae infection.

Technical Abstract: Frass -the by-product of the larva meal industry- shown to be sustainable source of a suitable ingredient for use in diets of several fish species. Additionally, because of its potential immunomodulatory activity and anti-microbial properties, frass may have great potential as attractive organic methods of pathogen control in aquaculture. The purpose of this study was to evaluate the changes in growth, hematology, serum chemistry, immune responses, and disease resistance of fingerling channel catfish, Ictalurus punctatus, fed diets containing frass from black soldier fly larvae, Hermetia illucens, fed on dried distiller's grain with solubles (DDGS). The catfish were maintained on diets with 0, 5, 10, 20 and 30% frass for 10 weeks. Fish in each aquarium were group-weighed and counted at 2-week intervals. At the end of the feeding trial, blood samples were collected from fish in all groups. Fish fed on the diet containing 10% or more frass had significantly higher weight gain than control fish. Similarly, hematological parameters -except white blood cell count, (WBC)- were improved with the inclusion of frass. Serum glucose (GL) levels were significantly lower in fish on the diet with frass than fish on the diet without frass. Fish fed the highest dietary levels of frass (30%) had a significantly higher serum cholesterol level than fish on the control diet. Serum complement activity was significantly higher in fish on diets containing frass at levels of 10% and 20%. No significant differences were observed in other measure serum components including albumin (ALB), alkaline phosphatase (ALP), alanine aminotransferase (ALT), amylase (AMY), calcium (CA), phosphorus (PHOS), potassium (K), total protein (TP), globulin (GLOB), thyroxine (T4), and lysozyme activity. Even though, overall mortality was low, fish on the diets containing frass at levels 20% or more showed significantly higher survival than that of control fish or fish on lower levels of dietary frass. Use of frass in the catfish diet may prove beneficial by improving hematological, some serum components and the resistance of juvenile channel catfish against F. covae infection.