Dietary sanguinarine supplementation on the growth performance, immunity and intestinal health of grass carp (Ctenopharyngodon idellus) fed cottonseed and rapeseed meal diets

Abstract

Sanguinarine (SG) is a plant alkaloid with demonstrated anti-inflammatory, antioxidant, and antimicrobial properties. However, its effects on the immunity and intestinal health of grass carp have not been clarified. Herein, an eight-week feeding trial was conducted to evaluate the effects of SG on the growth, immunity, and intestinal health of grass carp (Ctenopharyngodon idellus). A basal diet of 5% fish meal and 44% cottonseed and rapeseed meal was designated as the control diet (FM group). Diets (2% fish meal, 55% cottonseed and rapeseed meal) supplemented with four SG concentrations (0, 0.2, 0.4, and 0.8 g·kg−1; designated as the SG0, SG0.2, SG0.4, and SG0.8 groups, respectively) were prepared. The results indicate that dietary SG in high cottonseed and rapeseed meal diets increased the survival rate (SR), weight gain rate (WGR), superoxide dismutase (SOD), and alkaline phosphatase (AKP) activities compared with the SG0 group, but not significantly. The activity of malondialdehyde (MDA) was significantly lower in the SG0.2–0.8 groups than SG0 group. The SG0 group had a significantly decreased number of goblet cells and villus height/crypt depth (V/C), significantly downregulated mRNA expression levels of MnSOD, claudin, occludin, ZO-1, and ZO-2, and significantly upregulated mRNA expression levels of TNF-α, IL-1β, TLR-7, and TLR-8 compared with those in the FM group. While the number of goblet cells and V/C were significantly greater, the expression of MnSOD, ZO-1, and ZO-2 was significantly upregulated and the mRNA expression levels of TNF-α, IL-1β, IL-6, TLR-4, TLR-7, and TLR-8 were significantly downregulated in the SG0.8 group compared with those in the SG0 group. The proportion of Aeromonas significantly increased, and the Bacteroides significantly decreased in the SG0 group compared with the FM group. However, the proportion of Aeromonas showed significantly decreased, while the proportion of Bacteroides increased in the SG0.8 group compared with the SG0 group. Furthermore, based on microbial function, the gut microbiota of the SG0.8 group were more active concerning the energy, lipid, and amino acid metabolisms compared with those of the SG0 group. In conclusion, the feed with a higher cottonseed and rapeseed meal concentration negatively affects the SR, intestinal structure and immunity of grass carp. However, dietary SG can improve the SR and WGR by enhancing the intestinal morphology, microbiota structure, and mRNA expression levels of genes related to intestinal immunity.