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. 2021 Dec;7(4):1360-1370.
doi: 10.1016/j.aninu.2021.07.008. Epub 2021 Oct 11.

Insect (black soldier fly larvae) oil as a potential substitute for fish or soy oil in the fish meal-based diet of juvenile rainbow trout (Oncorhynchus mykiss)

Femi J Fawole  1   2   3 , Shyam N Labh  1   2 , Md Sakhawat Hossain  2   4 , Ken Overturf  5 , Brian C Small  2 , Thomas L Welker  5 , Ronald W Hardy  1 , Vikas Kumar  1   2
Affiliations

Insect (black soldier fly larvae) oil as a potential substitute for fish or soy oil in the fish meal-based diet of juvenile rainbow trout (Oncorhynchus mykiss)

Femi J Fawole et al. Anim Nutr. 2021 Dec.

Abstract

Alternative sources of fish oil (FO) are one of the major problems in aquaculture; therefore, the goal of the present study was to examine insect (black soldier fly larvae) oil (BSLO) as a potential replacer of fish/soy oil in juvenile rainbow trout (initial average weight of 32 ± 0.15 g) feed. Four diets were formulated wherein FO (control diet) was completely replaced with either soybean oil (SO) or BSLO, and an additional BSLO-based diet supplemented with 1.5% bile acid (BSLO + BA) were fed to the fish for 10 weeks. Growth performance of the BSLO fed group was similar (P > 0.05) to that of the FO and SO fed groups, however, the fish fed BSLO + BA diet registered the lowest growth (P < 0.05). Oil sources did not (P > 0.05) affect the major nutrient content of whole-body, however, the fatty acid composition of the muscle and liver was influenced (P < 0.05), with the highest 14:0, 16:0, and total saturated fatty acid detected in BSLO or BSLO + BA fed trout compared to the others (P < 0.001). No significant differences were observed in eicosapentaenoic acid + docosahexaenoic acid (EPA + DHA) or total n-3 polyunsaturated fatty acid (PUFA) content in muscle among the groups, whereas, the highest EPA:DHA and n-3:n-6 ratios were detected in the FO group. Gene expression for fatty acid binding protein (fabp), fatty acid synthase (fas), and Δ5 desaturase in the liver was lower in FO (P < 0.05), while BSLO + BA registered the highest Δ6 expression (P = 0.006). Supplementation of BA in the BSLO diet increased superoxide dismutase (SOD) and catalase (CAT) activities compared to the other groups (P < 0.05). In conclusion, BSLO could serve as a substitute for FO and SO in rainbow trout diet without negatively impacting growth performance, whole-body composition and nutrient retention, and modulate the expression of fatty acid metabolism-related genes in rainbow trout.

Keywords: Antioxidant enzyme; Fatty acid metabolism; Growth performance; Insect oil; Rainbow trout.

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Conflict of interest statement

We declare that we have no financial and personal relationships with other people or organizations that can inappropriately influence our work, and there is no professional or other personal interest of any nature or kind in any product, service and/or company that could be construed as influencing the content of this paper.

Figures

Fig. 1
Fig. 1
Principal component (PC) analysis of fatty acids allocation in the liver (L) and muscle (M) of rainbow trout fed with different dietary oil sources for 10 weeks. FO = fish oil; SO = soybean oil; BSLO = black soldier fly larvae oil; BA = bile acid; EPA = eicosapentaenoic acid; DHA = docosahexaenoic acid. Initial average weight of fish is 32 ± 0.0 g.
Fig. 2
Fig. 2
Relative mRNA expression of hepatic fatty acid metabolism related genes in rainbow trout fed diets containing fish oil (FO), soybean oil (SO), black soldier fly oil (BSLO), or BSLO + bile acid (BA) for 10 weeks. fabp = fatty acid-binding protein; fas = fatty acid synthase. Different lower case letters within the same gene denote statistically significant differences (P < 0.05). Data expressed as means ± SE (n = 9 × 2). Initial average weight of fish is 32 ± 0.0 g.
Fig. 3
Fig. 3
Serum superoxide dismutase (SOD) activity in rainbow trout fed diet containing fish oil (FO), soybean oil (SO), black soldier fly oil (BSLO), or BSLO + bile acid (BA) for 10 weeks. Different lower case letters between different dietary groups denote statistically significant differences (P < 0.05). Data expressed as means ± SE (n = 9). Initial average weight of fish is 32 ± 0.0 g.
Fig. 4
Fig. 4
Catalase (CAT) and glutathione peroxidase (GPx) enzyme activities in the serum of rainbow trout fed diets containing fish oil (FO), soybean oil (SO), black soldier fly oil (BSLO), or BSLO + BA (BSLO + bile acid) for 10 weeks. Different lower case letters between different dietary groups denote statistically significant differences (P < 0.05). Data expressed as means ± SE (n = 9). Initial average weight of fish is 32 ± 0.0 g.
Fig. 5
Fig. 5
Serum glucose concentration of rainbow trout fed diets containing fish oil (FO), soybean oil (SO), black soldier fly oil (BSLO), or BSLO + bile acid (BA) for 10 weeks. Different lower case letters between different dietary groups denote statistically significant differences (P < 0.05). Data expressed as means values ± SE (n = 9). Initial average weight of fish is 32 ± 0.0 g.
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