Effect assessment of tea polyphenols extracted from green tea on growth performance, immunity and gut microbiota &amp; metabonomics in juvenile hybrid sturgeon (Acipenser baerii♀ × A. schrenckii♂)
Authors: Zhao Zhenxin , Zhao Fei , Zhuoma Cairang , Zhang Xianbo , Luo Tianxun , Zhou Zhou , Zhou Qichun , Wang Jinle , Zhao Feng , Zhou Lu , Wang Qifu , Li Zhengyou , Zhang Xiaoping 
Published: January 2023

Background
Hybrid sturgeon (Acipenser baerii♀ × A. schrenckii♂) is widely cultivated in China and is highly susceptible to environmental stress and diseases, leading to substantial economic losses. Conversely, tea polyphenols (TPs) is regarded as a functional feed additives (antioxidants) derived from green tea which can improve oxidative stress resistance, meat quality, immunity, and growth performance in some fish species. However, the association between TPs and health status in juvenile hybrid sturgeon are unclear.
Methods
Here we aimed to assess the effects of dietary TPs levels on growth performance, intestinal immunity, microbiome, and metabolism of juvenile hybrid sturgeon. A total of 450 fish (97.20 ± 0.18 g) were randomly divided into a standard diet (TP-0) or four treatments consisting of a standard diet supplemented with four concentrations of TPs (mg / kg): 100 (TP-100), 300 (TP-300), 500 (TP-500), and 1000 (TP-1000) for 56 days. Growth performance was measured at the beginning and end of the study. Intestinal samples were collected to determine bacterial community structure and immune responses. The microbiota and its correlation with intestinal metabolism were analyzed by 16S rRNA gene high-throughput sequencing and gas chromatography-mass spectrometry.
Results
Our results showed that TP-300 significantly increased weight gain rate (WGR) and specific growth rate (SGR) (p < 0.05), and TP-1000 significantly increased the feed conversion ratio (FCR) (p < 0.05). TP-300 and TP-500 significantly increased intestinal trypsin, amylase, and lipase activities (p < 0.05). Besides, TP-300 significantly enhanced total antioxidant capacity (T-AOC) and the levels of superoxide dismutase (SOD), catalase (CAT), and glutathione (GSH) and decreased malondialdehyde (MDA) content (p < 0.05), as well as remarkably increased villus height (VH), crypt depth (CD), and the number of goblet cells (GC) in the mid-intestine, and TP-1000 decreased muscle thickness (MT) and villus width (VW) (p < 0.05). Moreover, TP-300 decreased the expression levels of tumor necrosis factor-alpha (TNF-α), interleukin 8 (IL-8), and interleukin 1β(IL-1β) compared with TP-0 and TP-1000 (p < 0.05). In addition, the intestinal microbiota diversity in the TP-300 group was observably higher, the dominant microbiota was Bacteroidota, Cyanobacteria, Proteobacteria and Firmicutes at the phylum level, Enterobacteriaceae, Nostocaceae and Clostridiaceae at the family level. and the relative abundances of potential probiotics including Rhodobacteraceae and potential pathogens especially Clostridiaceae were the highest, and lowest, respectively. Metabolomics analysis indicated that TP-300 improved the metabolic profile and modulated several metabolic pathways in juvenile hybrid sturgeon. The correlation analysis of 16S rRNA sequencing and metabolomics showed that intestinal microorganisms were significantly correlated with differential metabolites in the TPs-supplemented groups, suggesting that the microbiota mediated the effect of TPs on intestinal metabolism.
Conclusions
In summary, TP-300 altered the abundance of microbial taxa involved in differential metabolism, resulting in enhancing the intestinal digestion, antioxidant status and non-specific immunity to improve the growth performance in juvenile hybrid sturgeon.