Atlantic_salmon_mealworm_meal

A 12-week growth trial was conducted to assess the effects of mealworm meals, as a substitution for fish meal, on the growth, physio-biochemical responses, gut microbiome, and immune related genes expression of Atlantic salmon (Salmo salar). Twenty Atlantic salmon parr (38.5±0.1g, initial weight) were stocked into each of 16 tanks. A fish meal-based diet (100%FM) was used as the control treatment and was compared with three test diets where: 1) FM was partially (50%) replaced with defatted mealworm meal, Tenebrio molitor (50%DMM), 2) FM was fully replaced with defatted mealworm meal (100%DMM) and 3) FM was partially replaced with whole mealworm meal, Alphitobius diaperinus (50%WMM). All substitutions were done on a crude protein basis. Each of the four experimental diets were evaluated in quadruplicate tanks as part of randomized design. The results indicated that Atlantic salmon showed high survival rate (greater or equal to 98.8%), no significant difference in final growth, feed efficiency ratios and condition indices, except low hepatosomatic index in fish fed 100%DMM and 50%WMM compared to the control. Whole-body proximate and amino acids composition were not statistically different between treatments, while essential fatty acids including linolenic, eicosapentaenoic acid (EPA), and homo- a-linolenic, were lower in fish fed 100%DMM. Plasma parameters (total protein, alanine aminotransferase, alkaline phosphatase, and total iron-binding capacity) and hepatic peroxide and antioxidants (superoxide dismutase and glutathione peroxidase activities) were not significantly affected by dietary substitutions whereas plasma immunoglobulin M showed significantly higher levels in fish fed 50%DMM and 100%DMM when compared to the control. The inclusion of mealworm meals significantly impacted the beta-diversity but not alpha-diversity of the salmon gut microbiomes when compared to those fed the 100%FM control diet. The most common genus in all treatments was Pseudomonas, which has been previously shown to have both commensal and pathogenic members. The relative expressions of growth (insulin-like growth factor-I), protein synthesis (target of rapamycin signaling pathway regulator-like), and immune related (interferon‐gamma and interleukin-1beta) genes were not significantly different between fish fed the different dietary treatments. Overall, this study suggests that the mealworm meals tested are suitable alternatives to fish meal in the diet of Atlantic salmon.