Effects of herbal extracts (Foeniculum vulgare and Artemisia annua) on growth, liver antioxidant capacity, intestinal morphology and microorganism of juvenile largemouth bass, Micropterus salmoides

The effects of diets supplement Foeniculum vulgare extract (FE) and Artemisia annua extract (AE), single or combined, on the growth, liver antioxidant capacity and intestinal flora immunity of Micropterus salmoides were investigated. Largemouth bass juvenile (10.77 ± 0.02 g) were divided into 4 groups and each group was fed with diets supplemented with or without the medicinal herb extracts (additive quantity: 0.05%) for 8 weeks. The results showed that the largemouth bass fed with diets supplemented with AE or a combination of the FE and AE (FAE) significantly enhanced the specific growth rate (SGR) and feed intake (FI). Furthermore, the largemouth bass fed with two medicinal herbs alone or in combination significantly increased the antioxidant enzyme activities (SOD and CAT) and their gene expression levels, and decreased the malondialdehyde (MDA) content in the liver ( P < 0.05). In addition, AE supplement also significantly increased the number of intestinal villus, affected the intestinal bacterial structure, increased the abundance of Lactobacillus and Enterococcus , and decreased the abundance of Plesiomonas in the intestine( P < 0.05). Bugbase phenotypic prediction analysis indicated that fish fed with AE remarkably upregulated gram-positive bacteria and downregulated gram-negative bacteria, while potential pathogenicity was obviously reduced ( P < 0.05). All in all, this study revealed that AE can enhance the liver antioxidant capacity, improve intestinal morphology and regulate intestinal flora, thus promoting the growth of largemouth bass, and can be used as a feed additive to improve health and promote growth of fish. • Artemisia annua enhanced the growth performance. • Foeniculum vulgare and Artemisia annua improved the liver antioxidant capacity. • Artemisia annua extract could regulate the intestinal bacteria flora of M. salmoides .