Atlantic salmon (Salmo salar) farming in marine waters and in emerging land-based systems is a vital industry globally for a high demand product. As this industry continues to grow, fish nutrition research is the key factor for sustainable feed development and ultimately for sustainable aquaculture production. The purpose of this study was to evaluate the potential of two insect-based feed ingredients as alternatives to fish meal (FM) in the diets of Atlantic salmon using growth, physio-biochemical, gut microbiome, and nutrigenomics approaches.
A 12-week growth trial was conducted in an indoor recirculating system at the University of Maine, Aquaculture Research Institute. Twenty Atlantic salmon parr (38.5 ± 0.1g initial weight) were stocked into each of 16 experimental tanks. A control diet (FM-based diet), and three test diets [substitution of either 50% or 100%FM by defatted mealworm meal, Tenebrio molitor (50%DMM and 100%DMM) or by whole mealworm meal, Alphitobius diaperinus (50%WMM), on a crude protein basis] were evaluated as a completely randomized design with four replicates.
The study results indicated that Atlantic salmon showed high final growth, survival rate (greater or equal to 98.8%), as well as high feed efficiency ratios (FE) and condition indices when fed the experimental diets. Whole-body proximate and amino acids composition not statistically different between any treatments, while essential fatty acids (including EPA and ALA) were lower in fish fed 100%DMM. Plasma total protein, alanine aminotransferase, alkaline phosphatase and total iron-binding capacity were not significantly affected by dietary substitutions whereas immunoglobulin M showed significantly higher levels in fish fed 50%DMM and 100%DMM when compared to the control. Neither liver peroxides (malondialdehyde content) nor antioxidant enzymes (SOD and GPx activities) were significantly different between treatments. Dietary insect meal inclusion significantly impacted the beta-diversity of Atlantic salmon gut microbiomes. The most common genus in all treatments was Pseudomonas, which has been shown to have both pathogenic and commensal members in the literature. The relative expressions of growth (IGF-I) and immune related genes (TIPRL, IFN-γ and IL-1β) were not significantly different between fish fed the different dietary treatments. Overall, this study concluded that the insect meals tested have similar benefits to fish meal in the diet of Atlantic salmon.