Objective In order to provide reference for the application of condensed tannins in Micropterus salmoides feed, this study was conducted to assess the effects of short-term feeding condensed tannins on growth performance and liver health of large-sized M. salmoides.

Method A total of 600 fish with an initial weight of 510 (±10.4) g were selected and randomly divided into 4 groups, with 3 replicates per group and 50 fish per replicates. Fish in the control group were fed with basic diet (G1), while fish in the experimental groups were fed with basic diet supplemented with 0.1% (G2), 0.2% (G3) and 0.4% (G4) of condensed tannins, respectively. The experimental period was 30 d.

Result Compared with G1, the feed coefficient of fish in G4 was significantly increased by 17.44% (P < 0.05), while the survival rate was significantly decreased by 15.79% (P < 0.05); The abdominal fat rate of fish in G2, G3, and G4 were significantly decreased by 12.03%, 16.18%, and 13.69% respectively (P < 0.05). There was no significant difference in feed intake, weight gain rate, specific growth rate among all groups; The contents of serum glucose, total cholesterol, and triglycerides of fish in G4 were significantly decreased by 49.73%, 28.46% and 35.71%, respectively (P < 0.05), while the contents of serum low-density lipoprotein cholesterol of fish in G3 and G4 were significantly decreased by 38.71% and 51.61% respectively (P < 0.05). There was no significant difference in the contents of albumin, globulin, high-density lipoprotein cholesterol and the activities of alanine transaminase and glutamic transaminase among all groups; With the increase of dietary condensed tannins, the "fatty liver" status of large-sized M. salmoides was improved, the vacuolation and inflammatory infiltration of liver tissue were also weakened, and the liver lipid content and lipid droplet area ratio were significantly reduced.

Conclusion Dietary supplemented with 0.1% and 0.2% of condensed tannins had no significant effects on the survival rate and feed coefficient of large-sized M. salmoides. However, it could promote the metabolism of glucose and lipid, reduce liver fat and abdominal fat, and improve liver health of fish. If the evaluation is based on liver health, the appropriate concentration of condensed tannins in the diet of M. salmoides is 0.2%.