Dietary Supplementation with Encapsulated or Non-Encapsulated Sodium Butyrate Enhances Growth, Antioxidant Defense, Immunity, and Gut Health in Largemouth Bass (Micropterus salmoides)

Abstract

This study aimed to evaluate the effects of dietary supplementation with sodium butyrate (SB) in different forms on the growth performance, antioxidant capacity, immune response, and intestinal health of largemouth bass (Micropterus salmoides). Five diets were formulated: a basal diet (SB0), diets with 1000 (ESB1), 1500 (ESB2), and 2000 mg/kg encapsulated SB (ESB3), and a diet with 2000 mg/kg raw powder sodium butyrate (RSB, non-encapsulated). After 49 days of feeding trials, the ESB2 group exhibited significantly higher weight gain and specific growth rates and a lower feed coefficient than those of the SB0 group (p < 0.05). Compared with the SB0 group, proximal intestinal villus length and width were significantly increased in the ESB1, ESB2, and ESB3 groups (p < 0.05). The expressions of tight junction genes zo-1, claudin-1, and claudin-4 were up-regulated in these SB-supplemented groups and most pronounced in the ESB2 group (p < 0.05). Compared with the SB0 group, antioxidant enzyme activities (catalase and superoxide dismutase) and their gene expressions increased in the ESB1, ESB2, and RSB groups (p < 0.05). Immune-related genes il-10 and tgf-β1 were up-regulated in the ESB1 and ESB2 groups, while their il-8, il-1β, and tnf-α were down-regulated (p < 0.05). The ESB2 group had higher intestinal abundance of Firmicutes and Lactobacillus. In conclusion, dietary supplementation with 1500 mg/kg encapsulated SB (ESB2) improved growth, antioxidant capacity, immunity, and gut health in largemouth bass.

Keywords: Micropterus salmoides; antioxidant enzymes; encapsulation; growth performance; gut microbiota; immunity; sodium butyrate.

Figure 1

Histological HE staining results of intestinal tissue in five groups of largemouth bass. (A–E) HE staining of the proximal intestine; (F–J) HE staining of the mid intestine; (K–O) HE staining of the distal intestine.

Figure 2

Effects of dietary SB levels on intestinal tight junction gene expression in largemouth bass. (A) Expression of tight junction genes in the proximal intestine (PI); (B) expression of tight junction genes in the mid intestine (MI); (C) expression of tight junction genes in the distal intestine (DI). Different lowercase letters indicate significant differences between groups (p < 0.05), while the same lowercase letters indicate no significant differences (p > 0.05).

Figure 3

Effects of dietary SB levels on intestinal antioxidant enzyme activities and antioxidant gene expression in largemouth bass. (A) CAT and SOD enzyme activities in the proximal intestine (PI); (B) CAT and SOD enzyme activities in the mid intestine (MI); (C) CAT and SOD enzyme activities in the distal intestine (DI); (D) antioxidant gene expression in the proximal intestine (PI); (E) antioxidant gene expression in the mid intestine (MI); (F) antioxidant gene expression in the distal intestine (DI). Different lowercase letters indicate significant differences between groups (p < 0.05), while the same lowercase letters indicate no significant differences (p > 0.05).

Figure 4

Effects of dietary SB levels on intestinal immune gene expression in largemouth bass. (A) Immune gene expression in the proximal intestine (PI); (B) immune gene expression in the mid intestine (MI); (C) immune gene expression in the distal intestine (DI). Different lowercase letters indicate significant differences between groups (p < 0.05), while the same lowercase letters indicate no significant differences (p > 0.05).

Figure 5

Changes in the intestinal microbiota composition in different SB groups. (A) Intestinal microbiota composition analysis at the phylum level; (B) intestinal microbiota composition analysis at the genus level; (C) principal coordinate analysis (PCoA); (D) LEfse analysis of intestinal microbiota from phylum to genus.

Figure 6

Heatmap correlation analysis of intestinal microbiota at the phylum level and immune gene expression levels affected by SB. * Indicates p < 0.05, ** indicates p < 0.01, *** indicates p < 0.001.

Figure 7

Schematic of SB action on the intestine of largemouth bass. The red upward arrow indicates an increase in the enzyme activities, gene expressions or abundance of gut microbiota, while the blue downward arrow indicates a decrease in the enzyme activities, gene expressions or abundance of gut microbiota.