Abstract
This study investigated the effects of replacement of fishmeal (FM) with poultry by-product (PBM) protein, supplemented with black soldier fly, Hermetia illucens (HI) larvae on growth, histomormhology, immunity and resistance to Vibrio harveyi in juvenile barramundi. Two hundred and twenty five barramundi averaging 3.51 ± 0.03 g were randomly allocated into three groups and fed isonitrogenous and isocalorific diets containing different levels of PBM supplemented with HI as follows: Control (FM based diet), 45PBM + HI (45% PBM supplemented with 10% HI), and 90PBM + HI (90% PBM supplemented with 10% HI) for 6 weeks. Results showed that dietary inclusion of 45PBM + HI significantly improved the growth performance than control whereas growth inhibition occurred in the 90PBM + HI. The 45PBM + HI groups demonstrated significant increases in histometric measurements (villus and enterocyte width, and microvilli height) and acidic mucins. The impaired growth in 90PBM + HI groups was further associated with multifocal necrosis in the liver, an upregulation of the stress related genes (HSP70 and HSP90) and increase in the levels of liver enzymes. When 45PBM + HI was fed, survival against V. harveyi increased significantly and also an increase in serum immunity and immune-related genes in the head kidney was observed after infection.
Highlights
This study investigated the effects of replacement of fishmeal (FM) with poultry by-product (PBM) protein, supplemented with black soldier fly, Hermetia illucens (HI) larvae on growth, histomormhology, immunity and resistance to Vibrio harveyi in juvenile barramundi
Feeding juvenile barramundi with different levels of PBM supplemented with HI larvae significantly influenced the growth performance, biometry indices and feed utilization (Table 1)
When compared to the control, growth performance in terms of FBW, SGR and WG increased significantly (P < 0.05) in fish fed 45PBM + HI, while growth performance was significantly lower in 90PBM + HI groups
Summary
This study investigated the effects of replacement of fishmeal (FM) with poultry by-product (PBM) protein, supplemented with black soldier fly, Hermetia illucens (HI) larvae on growth, histomormhology, immunity and resistance to Vibrio harveyi in juvenile barramundi. Nogales-Mérida, et al.[26] reported that insect derivate products including protein concentrates, chitins, oils and antimicrobial peptides enhance the growth performance, but may boost the fish immunity. H. illucens (HI) belonging to the Diptera order is one of the promising source of insect protein due to containing from 40 to 54% crude protein and 15 to 49% crude lipid (dry matter basis), well-balanced amino acids similar to FM32,33, and being a good source of minerals and a variety of vitamins[28] Another important attribute of HI is the presence of antibacterial activity[30,34] which, in low doses, may boost the immunity to low doses dietary antibiotics[35]. Jian[36] clownfish, Amphiprion ocellaris[37] and Zebrafish, Danio rerio[38,39] have been investigated, information on the histological structure of juvenile barramundi when fed HI remains largely unknown
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