Carvacrol promotes intestinal health in Pengze crucian carp, enhancing resistance to Aeromonas hydrophila
Wenshu Liu, Xiaoze Guo, Yanliang Chen, Yanqiang Tang, Haihong Xiao, Siming Li
Abstract
This study was performed to determine the effects of dietary microencapsulated carvacrol (MC) on growth, resistance to A. hydrophila, and intestinal health parameters including intestinal bacteria, intestinal morphology and intestinal cytokines, in Pengze crucian carp (Carassius auratus var. Pengze). Fish were divided into four groups. Each group was fed a different diet for 56 days (a control diet or diets supplemented with 200, 400, or 600 mg/kg of MC). Our results indicate that MC had no effect on growth but significantly decreased A. hydrophila infection-associated mortality rates at 400 and 600 mg/kg and the lowest mortality was present at 600 mg/kg. The intestinal health of fish receiving the control diet was compared with that of the group receiving 600 mg/kg MC. High-throughput sequencing showed that MC increased the abundance of phylum Fusobacteria. It also increased the abundance of the genus Cetobacterium and decreased those of Flavobacterium and Pseudomonas. Light microscopy and transmission electron microscopy images support the ability of MC to improve the integrity of the lamina propria, increase microvilli height, and strengthen tight junctions, especially in the foregut. An ELISA assay indicated that levels of intestinal pro-inflammatory cytokines, including tumor necrosis factor-α and interleukins-1β, were reduced, whereas the level of the anti-inflammatory cytokine interleukins-10 was increased of fish administered dietary MC. We conclude that carvacrol promotes intestinal bacteria composition, intestinal morphology status and reduces intestinal inflammatory, which enhances resistance to A. hydrophila in Pengze crucian carp.