The present study aimed to investigate the effect of dietary of melatonin (MLT) and folic acid (FA) administrations on growth performance, antioxidant status, and liver histological structure of juvenile gilthead sea bream, Sparus aurata L. under standard rearing conditions. Four diets were considered: a basal diet considered a control and three diets supplemented with 40 mg/kg of melatonin (MLT), 2 mg/kg of folic acid (FA), and with the mixture of melatonin and folic acid (MLT + FA). Each diet was randomly allocated to triplicate groups of fish (mean initial weight was 2.99 ± 0.55 g) for 41 days. The obtained results clearly indicated that the melatonin-supplemented diet decreased significantly the growth performance parameters (final body weight, weight gain rate, and specific growth rate) and IGF-1 level of the gilthead sea bream, while the folic acid-supplemented diet has no significant effect on these parameters. The mixture supplementation of melatonin and folic acid has no significant effect on the growth parameters due to the possible interaction between melatonin and folic acid effects. Furthermore, fish fed with all experimental diets showed significantly higher superoxide dismutase activity (SOD) and protein sulfhydryl level (PSH) and lower lipid peroxidation level (TBARS) and catalase activity (CAT) which confirm their powerful antioxidant role. The acetylcholinesterase activity (ACHE) decreased in fish fed with all experimental diets. The underlying mechanisms of driving melatonin and folic acid to reduce acetylcholinesterase activity require further studies. The histological structure of liver of control S. aurata fish shows severe hepatic lipid accumulation in large vacuoles that diminished after dietary individual or mixture folic acid and melatonin supplementations over 41 days. This work proved that 2 mg/kg of dietary folic acid has a positive effect on the growth performance, oxidative stress defense, and hepatic lipid accumulation reduction in the gilthead sea bream fish. Under our experimental conditions, melatonin failed to improve the growth indexes WGR, SGR, and IGF-I. This study recommends the diet supplementation with a dose lower than 2 mg/kg of food due to the observed effects on tissue ACHE activity.

中文翻译：

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补充褪黑激素和叶酸对标准饲养条件下养殖的金头鲷（ Sparus aurata L.）的生长性能，抗氧化状态和肝脏组织学的影响

本研究旨在调查日粮褪黑素（MLT）和叶酸（FA）对少年金头鲷（ Sparus aurata ）的生长性能，抗氧化状态和肝脏组织学结构的影响 L.在标准饲养条件下。考虑了四种饮食：基础饮食被视为对照，三种饮食分别补充了40 mg / kg的褪黑素（MLT），2 mg / kg的叶酸（FA）以及褪黑素和叶酸的混合物（MLT + FA ）。将每种饮食随机分配给三组鱼（平均初始重量为2.99±0.55 g），持续41天。获得的结果清楚地表明，补充褪黑素的饮食显着降低了金头鲷的生长性能参数（最终体重，体重增加率和比生长率）和IGF-1水平，而补充叶酸的饮食具有对这些参数无明显影响。褪黑素和叶酸的混合物补充物对生长参数没有显着影响，因为褪黑素和叶酸的作用之间可能存在相互作用。此外，以所有实验饮食喂养的鱼均显示出明显更高的超氧化物歧化酶活性（SOD）和蛋白质巯基水平（PSH）以及更低的脂质过氧化水平（TBARS）和过氧化氢酶活性（CAT），这证明了其强大的抗氧化作用。用所有实验饮食喂养的鱼的乙酰胆碱酯酶活性（ACHE）降低。驱动褪黑激素和叶酸降低乙酰胆碱酯酶活性的潜在机制需要进一步研究。对照肝的组织学结构 用所有实验饮食喂养的鱼均显示出较高的超氧化物歧化酶活性（SOD）和蛋白质巯基水平（PSH），并且脂质过氧化水平（TBARS）和过氧化氢酶活性（CAT）较低，这证明了它们的强大抗氧化作用。用所有实验饮食喂养的鱼的乙酰胆碱酯酶活性（ACHE）降低。驱动褪黑激素和叶酸降低乙酰胆碱酯酶活性的潜在机制需要进一步研究。对照肝的组织学结构 用所有实验饮食喂养的鱼均显示出明显更高的超氧化物歧化酶活性（SOD）和蛋白质巯基水平（PSH），以及较低的脂质过氧化水平（TBARS）和过氧化氢酶活性（CAT），这证明了其强大的抗氧化作用。用所有实验饮食喂养的鱼的乙酰胆碱酯酶活性（ACHE）降低。驱动褪黑激素和叶酸降低乙酰胆碱酯酶活性的潜在机制需要进一步研究。对照肝的组织学结构 驱动褪黑激素和叶酸降低乙酰胆碱酯酶活性的潜在机制需要进一步研究。对照肝的组织学结构 驱动褪黑激素和叶酸降低乙酰胆碱酯酶活性的潜在机制需要进一步研究。对照肝的组织学结构 金黄色葡萄球菌 鱼在较大的液泡中显示出严重的肝脂质蓄积，在饮食中添加叶酸或褪黑激素或混合饮食超过41天后，这些脂质减少。这项工作证明了2 mg / kg的日粮叶酸对银头鲷鱼的生长性能，氧化应激防御和肝脂质蓄积减少具有积极作用。在我们的实验条件下，褪黑激素未能改善生长指数WGR，SGR和IGF-I。由于观察到的对组织ACHE活性的影响，该研究建议饮食补充剂量应低于2 mg / kg食物。