Dietary tributyrin modifies intestinal function by altering morphology, gene expression and microbiota profile in common carp ( Cyprinus carpio ) fed all‐plant diets

Abstract

Butyrate has received particular attention as growth and health promoters for aquatic organisms. To investigate the effects of dietary tributyrin (TB) on the intestinal function of common carp (Cyprinus carpio) fed all‐plant diets, five isoproteinic (320 g kg⁻¹) and isolipidic (70 g kg⁻¹) diets were formulated and fed to common carp (initial body weight about 8.1 g) for 8 weeks. The control diet (D1) contained 120 g kg⁻¹ fishmeal and 500 g kg⁻¹ plant protein blend (soybean, rapeseed and cottonseed meal), while the other four diets contained plant protein blend with TB at 0.5 g kg⁻¹ (D2), 1.0 g kg⁻¹ (D3), 2.0 g kg⁻¹ (D4) and 4.0 g kg⁻¹ (D5), respectively. Ultimately, high growth performance and low feed conversion ratios were observed in the fish fed the D1, D4, and D5 diets. Comparing to the D2 group, the intestinal trypsin, lipase, catalase, superoxide dismutase, and lysozyme activities, and the intestinal villi length and density were improved in the D4 and D5 groups (p < .05). Additionally, the transcript level of genes related to antioxidant function (cat, sod and gsh‐px), anti‐inflammatory cytokines (TGFβ and IL10), intestinal tight junction proteins (zo1, occludin, cldn3 and cldn11) and villification genes (cxd1, fat4, bmp2 and klf5) expression were also up‐regulated with the increasing dietary TB supplementation (p < .05). The relative abundance of Proteobacteria and Actinobacteria was decreased in the D2 group compared with the D1 group (p < .05), while these two bacterial abundances were significantly improved in the D4 and D5 groups (p < .05). Functional prediction of microbiota indicated that the Xenobiotics biodegradation and metabolism were increased in the high TB treatments (D3–D5) (p < .05). Taken the above results together, it can be concluded that the 2.0 g kg⁻¹–4.0 g kg⁻¹ TB shows the ability to modify the intestinal morphology, health, microbiota profile, leading to high growth performance in common carp fed all‐plant diets.