The objective of this study was to assess the effects of condensed tannins (CT) on growth performance and intestine health of juvenile Japanese seabass (Lateolabrax japonicus). Four diets were formulated to contain 0 (CT0), 100 (CT100), 200 (CT200) and 400 (CT400) mg/kg of pure CT isolated from grape seed. Quadruplicate groups of 20 fish were fed to apparent satiation two times daily during 56-days feeding trial. At the end of trail, the blood and intestine samples were collected to analyse serum metabolites, intestinal enzyme activity and histomorphology, and bacterial microbiomes of the fish. Results indicated that growth performance and intestinal histomorphology of fish were not affected by treatments. Fish fed CT200 and CT400 had lower (p < 0.05) serum lipopolysaccharide (LPS) than those fed CT0 and CT100. Activity of trypsin and Na⁺, K⁺-adenosine trisphosphatase (Na⁺, K⁺-ATPase) was lower (p < 0.05) in CT200 and CT400 than in CT0 and CT100. Over 93% of the sequences were classified within the Plesiomonas and Cetobacterium. The genera Plesiomonas increased (p < 0.05) and Cetobacterium decreased (p < 0.05) as dietary CT increase. Fish fed CT-containing diets had higher (p < 0.05) ACE, Chao 1 and Shannon bacterial diversity indices. A clear distinction of bacterial communities among treatments was noted as the plots cluster separately when the structure of bacterial communities was assessed using Bray–Curis distances. In conclusion, dietary CT up to 400 mg/kg did not affect growth performance but inhibited intestinal trypsin and Na⁺, K⁺-ATPase activities, decreased serum LPS and declined abundance of Cetobacterium. The increased bacterial diversity in fish fed CT-containing diets may due to the inhibitory effect of CT on Cetobacterium and Aeromonas, resulting in the increased genera such as Clostridium and Brevinema.

中文翻译：

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缩合丹宁酸对日本白鲟生长性能、肠道免疫能力和细菌微生物群落的影响

本研究的目的是评估浓缩单宁 (CT) 对日本鲈鱼 ( Lateolabrax japonicus )幼鱼生长性能和肠道健康的影响。四种饮食被配制为含有 0 (CT0)、100 (CT100)、200 (CT200) 和 400 (CT400) mg/kg 从葡萄籽中分离的纯 CT。在 56 天的饲喂试验中，每组 20 条鱼每天饲喂两次以达到明显的饱腹感。在试验结束时，收集血液和肠道样本以分析鱼的血清代谢物、肠道酶活性和组织形态学以及细菌微生物组。结果表明，鱼的生长性能和肠道组织形态不受处理的影响。喂食 CT200 和 CT400 的鱼的 ( p < 0.05) 血清脂多糖 (LPS) 与饲喂 CT0 和 CT100 的相比。 CT200 和 CT400中胰蛋白酶和 Na ⁺ , K ⁺ -腺苷三磷酸酶(Na ⁺ , K ⁺ -ATPase) 的活性低于CT0 和 CT100 ( p < 0.05)。超过 93% 的序列被归类为Plesiomonas和Cetobacterium。 随着饮食 CT 的增加，Plesiomonas属增加 ( p  < 0.05) 和Cetobacterium减少 ( p < 0.05)。喂食含 CT 日粮的鱼有更高的 ( p < 0.05) ACE、Chao 1 和 Shannon 细菌多样性指数。当使用 Bray-Curis 距离评估细菌群落的结构时，由于地块单独聚集，因此注意到处理之间细菌群落的明显区别。总之，日粮 CT 高达 400 mg/kg 不会影响生长性能，但会抑制肠道胰蛋白酶和 Na ⁺ , K ⁺ -ATPase 活性，降低血清 LPS 并降低Cetobacterium丰度。饲喂含 CT 饮食的鱼的细菌多样性增加可能是由于 CT 对Cetobacterium和Aeromonas的抑制作用，导致梭菌和Brevinema等属增加。