Effects of zymolytic black soldier fly (Hermetia illucens) pulp as dietary supplementation in largemouth bass (Micropterus salmoides)

Abstract

Black soldier fly (Hermetia illucens) larvae (BSFL) have been regarded as one of the most promising animal protein sources suitable for replacing fishmeal. In this study, the effects of the different diet levels (0%, 1%, 3% and 5%) of zymolytic black soldier fly pulp (ZBSFP) were investigated on growth performance, biological parameters and the cumulative mortality challenged with Aeromonas hydrophila of largemouth bass (Micropterus salmoides). After the feeding trial lasted for 56 days, the results indicated that 1% ZBSFP had a significantly higher final body weight (FBW), weight gain rate (WGR), feed intake (FI), and specific growth rate (SGR) but a significantly lower hepatosomatic index (HIS) that improved growth, and decreased 72 h cumulative mortality rates after challenged with A. hydrophila. Meanwhile, 1% ZBSFP had improved antioxidant activity and decreased oxidative metabolites. Furthermore, comparison of the intestinal microbial composition with 0% and 1% ZBSFP revealed that the dominant phylum Tenericutes replaced with Fusobacteria, and the most abundant genus Mycoplasma of Tenericutes was replaced with Cetobacterium of Fusobacteria at the microbial composition level. At the microbial potential function level, the metabolism of amino acids, energy and nucleotides was increased, while the metabolism of glycans and lipids was decreased, and notably, α-N-acetylglucosaminidase increased. These results indicated that 1% ZBSFP was an appropriate additive ingredient for replacing fish meal and that excessive addition may lead to side effects on largemouth bass. This study is beneficial for defining the proper addition of ZBSFP to largemouth bass.

Keywords

• Black soldier fly
• Enzymatic hydrolysis
• Largemouth bass
• Effects
• Intestinal microbiota