Effect of dietary Tenebrio molitor protein on growth performance and immunological parameters in Macrobrachium rosenbergii

Five diets were formulated with 0% (control), 4% (D4), 8% (D8), 12% (D12), and 16% (D16) Tenebrio molitor protein in prepared aquafeed to investigate the effects of T. molitor protein on growth performance, immunological parameters, and resistance against Lactococcus garvieae and Aeromonas hydrophila in Macrobrachium rosenbergii for 10 weeks. The weight gain (WG), percentage of weight gain (PWG), daily growth rate (DGR), specific growth rate (SGR), and protein efficiency ratio (PER) of D12 were significantly higher than those of the control, D4, and D8, but not significantly different from those of D16. The condition factor (K), feed conversion ratio (FCR), and survival rate (SR) did not differ significantly among groups. Lipid content decreased and protein content increased in the carcass and muscle of prawns as T. molitor protein contents increased. The total haemocyte count (THC) and numbers of semigranular cells (SCs), granular cells (GCs), and hyaline cells (HCs) significantly increased from the control to D16. Increased activities of superoxide dismutase (SOD), phenoloxidase (PO), lysozyme (LZ), and alkaline phosphatase (ALP) were detected as T. molitor protein contents increased. mRNA expression of prophenoloxidase (proPO), lipopolysaccharide- and β-1,3-glucan-binding protein (LGBP), peroxinectin (PE), and α2-macroglobulin (α2-M) increased in haemocytes of M. rosenbergii from the control to D16. Phagocytosis of L. garvieae and the relative survival rate (RPS) against A. hydrophila were positively correlated with activities of protective enzymes and expression of proPO system immune-related genes in prawns fed diets with T. molitor protein. These results demonstrated that dietary inclusion of 12% T. molitor protein had the best effects on growth performance, immunological parameters, and resistance against L. garvieae and A. hydrophila, when balanced against the additional feed cost. This study supports the inclusion of T. molitor protein in functional aquafeed.