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; Shyam N Labh; Md Sakhawat Hossain; Ken Overturf; Brian C Small; Thomas L Welker; Ronald W Hardy; Vikas Kumar

doi:10.1016/j.aninu.2021.07.008

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)

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

Authors

Femi J Fawole^{1

2

3}, Shyam N Labh^{1

2}, Md Sakhawat Hossain^{2

4}, Ken Overturf⁵, Brian C Small², Thomas L Welker⁵, Ronald W Hardy¹, Vikas Kumar^{1

2}

Affiliations

¹ Aquaculture Research Institute, Department of Animal, Veterinary and Food Sciences, University of Idaho, Moscow, ID, 83844, USA.
² Hagerman Fish Culture Experiment Station, Aquaculture Research Institute, University of Idaho, Hagerman, ID, USA.
³ Department of Aquaculture and Fisheries, University of Ilorin, Ilorin, Nigeria.
⁴ Department of Aquaculture, Faculty of Fisheries, Sylhet Agricultural University, Sylhet, 3100, Bangladesh.
⁵ United States Department of Agriculture, Agricultural Research Service, Hagerman Fish Culture Experiment Station, Hagerman, ID, USA.

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.