Guar gum improves growth performance, intestinal microbiota homeostasis, and hepatic lipid metabolism in juvenile largemouth bass (Micropterus salmoides) fed high-fat diets

The study aimed to investigate the effects of guar gum on the growth performance, gut microbiota composition, and hepatic lipid metabolism of largemouth bass (Micropterus salmoides) fed high-fat diets. Experimental fish were fed a normal-fat diet (Control), high-fat diet (HF), or HF diets supplemented with 0.3 %, 1 %, and 3 % guar gum (GG0.3, GG1, and GG3, respectively) for eight weeks. The results showed that HF significantly decreased fish growth performance, increased hepatic lipid accumulation, upregulated the expression of sterol regulatory element binding proteins 1 (SREBP1), and downregulated the expression of liver X receptor alpha (LXR alpha), cy-tochrome P450 7A1 (CYP7A1), and CYP8B1, compared to Control. However, these problems of high-fat diets were significantly alleviated by GG 0.3. The intestinal microbial communities of the GG0.3 and Control were similar but distinctly different from that of the HF group. Compared to HF, GG0.3 significantly increased the relative abundances of Firmicutes and Lactococcus and decreased the relative abundance of Tenericutes, Meso-mycoplasma, and Phenylobacterium. In addition, the GG0.3 and GG1 treatments significantly enhanced the bile salt hydrolase (BSH) activity in the digesta compared to HF. In conclusion, 0.3 % guar gum supplementation can improve growth performance, intestinal health, and hepatic lipid metabolism in fish fed high-fat diets.