The present study investigated possible effects of dietary malic acid on the expression of immunity, antioxidant and growth related genes expression as well as skin mucus immune parameters in common carp. Common carp (Cyprinus carpio) fingerlings were fed diets supplemented with different levels (0 [control], 0.5%, 1%, 2%) of malic acid (MA) for 60 days. The results revealed highest expression levels of immune-related genes (tnf-alpha, il1b, il8 and lyz) in skin of common carp fed 2% MA (P < 0.05). Regarding 1% MA treatment comparison with control group, significant difference was noticed just in case of lyz (P < 0.05). Evaluation of growth related genes expression revealed no significant difference between treatments (P > 0.05). The study of antioxidant related genes (gsta and gpx) in common carp skin fed with MA, showed significant difference between treated groups and control (P < 0.05). Carps fed with 2% MA had highest alkaline phosphatase activity in skin mucus compared other treated groups and control (P < 0.05). There were no significant difference between 0.5% and 1% and control (P > 0.05). The study of total protein and total immunoglobulin (Ig) in common carp skin musus revealed no alteration following MA treatment (P > 0.05). The present data demonstrated that feeding with MA altered immune and antioxidant genes expression in skin mucus of common carp.

中文翻译：

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苹果酸丰富鲤鱼的饮食：对皮肤粘膜免疫力，抗氧化能力和生长性能的影响

本研究调查了日粮苹果酸对鲤鱼免疫力，抗氧化剂和生长相关基因表达以及皮肤粘液免疫参数表达的可能影响。鲤鱼（Cyprinus carpio）鱼种饲喂了补充了不同水平（0 [对照组]，0.5％，1％，2％）苹果酸（MA）的日粮，持续60天。结果显示，饲喂2％MA的鲤鱼的皮肤中免疫相关基因（tnf-alpha，il1b，il8和lyz）的最高表达水平（P <0.05）。关于与对照组的1％MA治疗比较，仅在lyz的情况下发现显着差异（P ＜0.05）。对生长相关基因表达的评估显示治疗之间无显着差异（P> 0.05）。饲喂MA的鲤鱼皮中抗氧化剂相关基因（gsta和gpx）的研究表明，治疗组与对照组之间存在显着差异（P <0.05）。与其他治疗组和对照组相比，饲喂2％MA的鲤鱼的皮肤粘液中碱性磷酸酶活性最高（P <0.05）。0.5％和1％与对照组之间无显着差异（P> 0.05）。对鲤鱼皮肤粘液中总蛋白和总免疫球蛋白（Ig）的研究表明，MA处理后未发生任何变化（P> 0.05）。目前的数据表明，饲喂MA可以改变鲤鱼皮肤粘液中的免疫和抗氧化基因表达。