Yellow mealworm (Tenebrio molitor) meal replacing dietary fishmeal alters the intestinal microbiota, anti-oxidation and immunity of large yellow croaker (Larimichthys crocea)

Abstract

The present study investigated the impact of dietary fishmeal replacement with yellow mealworm (Tenebrio molitor) meal (TM) on the anti-oxidation, immunity and intestinal microbiota of large yellow croaker (Larimichthys crocea), with an initial body weight of 189.18 ± 0.13 g. Seven isonitrogenous and isolipidic diets were made using TM replacing the fishmeal at 0 % (TM0), 15 % (TM15), 30 % (TM30), 45 % (TM45), 60 % (TM60), 75 % (TM75) and 100 % (TM100), respectively. Each experimental diet was randomly assigned to three replicate groups of large yellow croaker (100 fish per group). After an 80-day feeding trial, it was showed that the activities of maltase, lysozyme and acid phosphatase in intestine, as well as serum albumin concentration and total anti-oxidative capacity in serum of fish fed diets with TM replacing fishmeal more than 60 % (P < 0.05). The intestinal muscularis thickness and perimeter-to-diameter ratio decreased significantly in TM75 and TM100 groups compared to the control (P < 0.05). At the transcriptional level, the mRNA expression of occludin, zonula occludens-1 (zo-1), oligopeptide transporter 1 (pept1), and oligopeptide transporter 2 (pept2) in the intestine, along with nuclear factor erythroid 2-related factor 2 (nrf2) and interleukin-10 (il-10) in both the intestine and liver, were linearly downregulated as the fishmeal replacement level increased (P < 0.05). While the relative expression levels of kelch-like ECH-associated protein 1 (keap-1), nuclear factor-κB (nf-κb) and tumor necrosis factor-α (tnf-α) in the intestine and liver were linearly upregulated with increasing dietary fishmeal replacement levels (P < 0.05). Besides, increasing dietary fishmeal replacement levels maintained intestinal microbiota alpha diversity (P > 0.05), while altering the intestinal microbial composition (P < 0.05). In conclusion, replacing 45 % of fishmeal with TM (equivalent to 25.57 % TM in diet) had no significant negative effects on the intestinal microflora, anti-oxidation and immunity of large yellow croaker.