This study was performed to determine effects of dietary isoleucine (Ile) on growth performance, and intestinal immunological and physical barrier function of hybrid catfish Pelteobagrus vachelli × Leiocassis longirostris. Six hundred and thirty fish (33.11 ± 0.09 g) were randomly divided into seven experimental groups with three replicates each, and respectively fed seven diets with 5.0, 7.5, 10.0, 12.5, 15.0, 17.5, and 20.0 g Ile kg⁻¹ diets for 8 weeks. The results showed improvement of growth performance, feed intake, feed utilization, relative gut length (RGL), and intestinal fold height and width by dietary Ile (P < 0.05). Meanwhile, dietary Ile (12.5 g kg⁻¹ diet) improved the activities of lysozyme (LZM), acid phosphatase, alkaline phosphatase and the contents of complement 3 (C3), C4, and immunoglobulin M (IgM) (P < 0.05). The c-type-lectin, c-LZM, g-LZM, and hepcidin mRNA expressions in the intestine were up-regulated in fish fed diets with 10.0–20.0 g Ile kg⁻¹ diet (P < 0.05). Dietary Ile (10.0–12.5 g Ile kg⁻¹ diet) increased intestinal β-defensin mRNA expression partially in association with Sirt1/ERK/90RSK signaling pathway. Dietary Ile (12.5–15.0 g Ile kg⁻¹ diet) decreased oxidative damage and improved antioxidant ability by increasing activities and expressions of superoxide dismutase, glutathione peroxidase, and glutathione reductase, glutathione-S-transferase (P < 0.05). The occludin, ZO-1, ZO-2, claudin3, and claudin 7 mRNA expressions in the intestine were up-regulated in fish fed diets with 10.0 and 12.5 g Ile kg⁻¹ diet (P < 0.05), whereas the myosin light chain kinase gene expression was decreased in fish fed diets with 7.5–17.5 g Ile kg⁻¹ diet. Dietary Ile (10–12.5 g Ile kg⁻¹ diet) decreased apoptotic responses by reducing the expression of caspase3 and caspase 9 via the AKT/TOR signaling pathway. Based on the quadratic regression analysis of PWG, the dietary Ile requirement of hybrid catfish was estimated to be 12.43 g Ile kg⁻¹ diet, corresponding to 32.05 g Ile kg⁻¹ dietary protein. Collectively, dietary Ile improved growth performance and immunological and physical barrier function of intestine in hybrid catfish.

本研究旨在确定饮食中异亮氨酸（Ile）对杂交of鱼Pelteobagrus vachelli  ×  Leiocassis longirostris的生长性能以及肠道免疫和物理屏障功能的影响。将630条鱼（33.11±0.09 g）随机分为七个实验组，每组三个重复，分别喂食7种日粮，分别为5.0、7.5、10.0、12.5、15.0、17.5和20.0 g Ile kg - ¹日粮。 8个星期。结果表明，通过饲料中的Ile可以改善生长性能，采食量，饲料利用率，相对肠道长度（RGL）和肠折叠高度和宽度（P  <0.05）。同时，饮食中的Ile（12.5 g kg ^-1饮食）改善了溶菌酶（LZM），酸性磷酸酶，碱性磷酸酶的活性以及补体3（C3），C4和免疫球蛋白M（IgM）的含量（P  <0.05）。10.0-20.0 g Ile kg ^-1饮食的鱼饲料中肠中的c型凝集素，c-LZM，g-LZM和hepcidin mRNA表达上调（P  <0.05）。饮食中的Ile（10.0–12.5 g Ile kg ^-1饮食）可增加肠道β-防御素mRNA表达，部分与Sirt1 / ERK / 90RSK信号通路相关。膳食中的Ile（12.5–15.0 g Ile kg ^-1饮食）通过增加超氧化物歧化酶，谷胱甘肽过氧化物酶和谷胱甘肽还原酶，谷胱甘肽S-转移酶的活性和表达来减少氧化损伤并提高抗氧化能力（P  <0.05）。喂鱼量为10.0和12.5 g Ile kg ^-1的鱼饲料中，肠中的occludin，ZO-1，ZO-2，claudin3和claudin 7 mRNA表达上调（P  <0.05），而肌球蛋白轻链在以7.5–17.5 g Ile kg ^-1的饲料喂养的鱼中，激酶基因表达降低。膳食岛（10-12.5克异亮氨酸千克^-1饮食）通过降低凋亡蛋白酶的表达减少细胞凋亡反应和caspase 9经由AKT / TOR信号通路。根据PWG的二次回归分析，杂种cat鱼的日粮Ile需求量估计为12.43 g Ile kg - ¹日粮，相当于32.05 g Ile kg - ¹日粮蛋白质。总的来说，饮食中的Ile改善了杂交hybrid鱼的生长性能以及肠道的免疫和物理屏障功能。