The effects of sodium propionate on intestinal barrier function of genetically improved farmed tilapia in a high-lipid formulation

Abstract

Sodium propionate has long been used as a feed additive in fish diets for its remarkable anti-mold properties. In this study, two-month old genetically improved farmed (GIF) tilapia (initial weight 0.55 ± 0.0004 g/fish) were fed with five isonitrogenous diets, including a low-fat diet (LFD), high-fat diet (HFD), 0.25% sodium propionate-supplemented HFD (HFSP0.25), 0.5% sodium propionate-supplemented HFD (HFSP0.5) and 1.0% sodium propionate-supplemented HFD (HFSP1.0). This study investigated the effects of sodium propionate on fish growth performance, intestinal epithelium integrity and permeability, intestinal “physiological hypoxia” and gut microbiota composition of GIF tilapia fed with the HFD. After a four-week feeding trial, sodium propionate supplementation (0.25%, 0.5% and 1.0%) had no effects on survival rate, body weight gain and feed conversion ratio of GIF tilapia. However, feeding the HFSP0.5 and HFSP1.0 impaired tight junctions and lamina propria compared to feeding the HFD (P < 0.05). Serum fluorescence intensities of fish fed the HFSP0.5 and HFSP1.0 were higher than that fed the HFD after an oral gavage of fluorescein isothiocyanate-labeled carboxymethylated dextran (P < 0.05). Besides, the level of serum endotoxin was higher in fish fed the HFSP1.0 (P < 0.05). The expressions of genes encoding tight junction-related proteins including occludin and claudin-1 were remarkably decreased by feeding the HFSP0.5 and HFSP1.0 (P < 0.05). Moreover, intestinal pimonidazole retention was significantly reduced by HFSP1.0 feeding (P < 0.05). Furthermore, feeding the HFSP0.5 significantly increased the relative abundance of Cetobacterium somerae (P < 0.05) while feeding the HFSP1.0 significantly increased the relative abundance of Plesiomonas shigelloides (P < 0.05) in the gut. Consistently, the presence of Cetobacterium somerae was observed in the liver and muscle of fish fed the HFSP0.5 as well as in the muscle of fish fed the HFSP1.0. Presence of Plesiomonas shigelloides was observed in the liver of fish fed the HFSP1.0. In conclusion, higher levels of sodium propionate (0.5% and 1.0%) disrupt intestinal epithelium integrity and increase intestinal permeability of GIF tilapia when fed a HFD. Besides, sodium propionate at 1.0% additive amount abolishes intestinal “physiological hypoxia”. Sodium propionate supplementation alters the species diversity and composition of gut microbial community.