Beneficial effects of the butanoic acid derivative tributyrin on the growth, immunity and intestinal health of large mouth bass (Micropterus salmoides)

Abstract

Tributyrin (TB) is a novel butanoic acid derivative with potent bioactive functions. In this study, an eight-week feeding trial aimed to investigate the effects of dietary TB on the growth, immunity and intestinal health of large mouth bass (Micropterus salmoides). Five experimental diets containing 0, 0.5, 1.0, 1.5 or 2.0 g/kg tributyrin were formulated and were regarded as TB0 (control), TB0.5, TB1.0, TB1.5 and TB2.0, respectively. Quadruplicate groups (four tanks per group, 30 fish per tank) of juvenile M. salmoides (initial weight: 20.00 ± 1.00 g) were fed to apparent satiation two times daily. After the feeding trial,Aeromonas hydrophila challenge tests were conducted and the A. hydrophila strains were subsequently sampled. As a result, the weight gain rate (WGR) was increased in the TB supplementation groups, and the TB1.5 group obtained the highest value. Furthermore, TB administration improved immune function. The content of serum complement 4 in the TB1.5 group was significantly higher than that in the control group. Increase of lysozyme activity and immunoglobulin M were significant in TB1.0 group than the control group. After A. hydrophila injection, TB1.0, TB1.5 and TB2.0 groups presented markedly higher survival rates than did the control group. Additionally, TB markedly enhanced the activities of amylase and lipase in the gut. Moreover, 16S rRNA sequencing revealed that TB could affect the intestinal microflora composition. Compared to those in the control group, the abundance of Fusobacteria were lower in the TB1.0 and TB1.5 groups. In conclusion, this study demonstrated that TB can improve the growth, immunity and intestinal health of M. salmoides, and the optimal dietary level of TB is determined to be 0.15%.