Combination of herbal extracts regulates growth performance, liver and intestinal morphology, antioxidant capacity, and intestinal microbiota in Acrossocheilus fasciatus

In the present study, the herbal extracts (RPTS) composed of Rheum palmatum: Schisandra sphenanthera: Terminalia chebula: Punica granatum with a weight ratio of 1.07: 3.00: 1.18: 1.38, was evaluated through a bacteriostatic assay in vitro. Afterwards, a 56-day feeding trial was operated to assess the impact of dietary RPTS at the dose of 0, 1.0, 2.5, 5.0, and 10 g·Kg−1 feed (entitled as Con, RPTS010, RPTS025, RPTS050, RPTS100 group, respectively) on the performance of Acrossocheilus fasciatus fingerlings. The results revealed that dietary RPTS at the dose of 2.5 g·Kg−1 feed remarkably improved the specific growth rate (SGR), and the gastrointestinal trypsin activity, as well as the catalase (CAT) activities, while slightly increased the alanine aminotransferase (ALT) activity and aspartate aminotransferase (AST) activity in the fish liver. Histological examination indicated that dietary high dose of RPTS (5.0 and 10.0 g·Kg−1 feed) could induce hepatic cell vacuolization and reduce the intestinal villi density of fish. Furthermore, the analysis of intestinal microbiota showed that Bacteroidota, Firmicutes and Proteobacteria were the three dominant phylum in all experimental groups, while the Firmicutes/Bacteroidota ratio exhibited a trend of initially decreasing followed by rising, with the supplementation level of RPTS increase. Additionally, the LEfSe analysis revealed that Cetobacterium was the most impacted species, which notably increased in RPTS025 group. Collectively, this study unveiled that the impact of dietary RPTS on fish performance was in a dose-dependent manner, and dietary RPTS at the dose of 2.5 g·Kg−1 feed could potentially enhance growth performance, digestive and antioxidant capacity, and positively modulate the intestinal microflora, without significantly impact liver health of A. fasciatus. •Evaluating the in vitro antibacterial effect of the novel formula (RPTS) composed of four herbal extracts.•Dietary RPTS (2.5 g·Kg−1 feed) promoted the intestinal Cetobacterium content in A. fasciatus.•Dietary RPTS did not affect the intact mucosal folds, muscularis and tunica propria of the intestine in A. fasciatus•High dose of RPTS induced hepatic cell vacuolization and reduced the intestinal villi density of A. fasciatus.