由于环境保护和成本控制的需要，植物性饲料原料在水产配合饲料中的用量越来越高。植物性原料中含有丰富的膳食纤维 (DFs)，使许多商品饲料中的DFs达30%以上，但由此带来的对水产动物的生理影响仍鲜受关注。本文介绍了DFs的定义、分类、理化特性、可发酵性及常见植物性饲料原料中DFs的含量，重点介绍了作者及团队在鱼类DFs营养生理方面的研究发现。研究表明，黄颡鱼摄食含20%~30% DFs的饲料后会出现出血、白便、肠炎、腐皮、烂鳃、肝脂肪变性和纤维化、绿肝、白肝、胆囊肿大等症状及暴发性死亡。大口黑鲈和草鱼摄食高DFs饲料后也有相似症状。DFs的致病作用不仅与饲料中DFs含量有关，还与DFs种类有关，果胶对黄颡鱼的致病性比纤维素强得多。DFs的致病机制与其对胆汁酸 (BAs)稳态和肠道微生物稳态的干扰有关。因DFs具有结合BAs的特性，这会阻碍BAs对法尼醇X受体 (FXR)等BAs受体的激活，而FXR负反馈调控BAs的合成并抑制炎症反应，因此，大量DFs进入肠道后就会引起BAs合成亢进，提高组织中BAs水平及其疏水性并干扰BAs循环节律，再由BAs的细胞毒性引起炎症反应和组织坏死。DFs还具有可发酵性，引起肠道微生物结构改变，或由BAs的抗菌作用引起肠道微生物结构改变，进而加剧包括BAs在内的代谢紊乱。DFs的致病性与其他胁迫作用具有叠加效应，加重疾病症状和进展。从DFs的致病机制出发，通过控制DFs摄入种类和摄入量、向饲料中添加BAs及牛磺酸、防止DFs与其他胁迫因子的叠加效应等方式可防控DFs诱导的疾病。本研究首次阐述了DFs过量摄入对鱼类的致病性及其潜在机制，为植物性饲料原料的高值化利用及饲料配制技术优化提供了新视角，为鱼类病害防控提供了新途径。研究结果也提示未来应进一步阐明不同植物性原料中DFs的种类、含量和特性以及水产动物对DFs的耐受范围。

Due to the needs of environmental protection and cost control, the amount of plant feedstuffs used in aquatic formula feed is increasing. Plant feedstuffs are rich in dietary fibers (DFs), which resulted in over 30% of DFs contained in common commercial aquatic commercial feeds. However, their impacts on fish physiology are still largely overlooked. This article introduces the definition, classification, physicochemical properties, fermentability, and content of DFs in common plant feedstuffs, with a focus on the research findings of the author and team in the fish physiology of DFs. We noticed that hemorrhage, white feces, enteritis, skin-rotting, gill-rotting, hepatic steatosis and fibrosis, green liver, white liver, gallbladder enlargement and even mass deaths could be induced in yellow catfish (Pelteobagrus fulvidraco) when diet included 20%-30% DFs. Similar symptoms had also been observed in largemouth bass (Micropterus salmoides) and grass carp (Ctenopharyngodon idella) fed high DFs diet. The pathogenic effect of DFs was related not only to the content of DFs in the diet but also to the types of DFs. Pectin was much more pathogenic to P. fulvidraco than cellulose. The pathogenic mechanism of DFs is related to their interference with bile acids (BAs) homeostasis and intestinal microbial homeostasis. DFs have the capacity of binding to BAs, which prevents BAs from activating BA receptors such as FXR. FXR negative feedback regulates the synthesis of BAs and inhibits inflammatory reactions. As a result, high levels of DFs caused hypersynthesis of BAs, increasing of the BAs level in tissues and their hydrophobicity, and interfed with the circadian rhythm of BAs, further inducing inflammatory reactions and tissue necrosis due to the cytotoxicity of BAs. Some DFs are fermentable, which caused structural changes in the gut microbiota (might also be duo to the antibacterial effect of BAs). The disorder of intestinal microbial homeostasis further aggravates metabolic disorders, including BAs metabolic disorder. The disease symptoms and progression induced by DFs can also be improved by the other stress factors. Based on the pathogenesis of DFs, the diseases can be prevented and controlled by limiting the intake of DFs, adding BAs and taurine to the diet, and avoiding the superposition effect of DFs with other stress factors. This study for the first time elucidates the pathogenicity of excessive intake of DFs on fish and its potential mechanisms, providing a new perspective for the high-value utilization of plant feedstuffs and optimization of feed formulation, suggesting a new approach for fish disease prevention and control. Further clarification should be provided on the types, levels, and characteristics of DFs in different plant feedstuffs, as well as the tolerance range of aquatic animals to DFs.

S 963.1

江苏省碳达峰碳中和科技创新专项资金(BE2022422)；江苏省现代农业(大宗鱼类)产业技术体系(JATS[2023]369, 117)