A 10-week feeding trial, followed by 24-h nitrite stress, was performed to evaluate the effects of dietary selenium-L-methionine (Se-Met) on growth, Se accumulation, antioxidant capacity, transcripts of selenoproteins and histological changes of muscle as well as resistance to nitrite stress in spotted seabass (Lateolabrax maculatus) reared at optimal (27 °C) and high (33 °C) temperatures. Five experimental diets were formulated to contain 0, 0.9, 1.8, 3.5, and 7.0 mg Se-Met/kg. Each diet was fed to fish (2.60 ± 0.2 g) in two parallel treatments at 27 or 33 °C. The results showed that elevated temperature (33 °C) induced thermal stress in fish, and fish under thermal stress exhibited lower weight gain and hepatosomatic index but a higher condition factor compared to those reared at 27 °C. However, the growth and feed utilisation were promoted in L. maculatus with 0.9 to 3.5 mg/kg Se-Met treatments. The protein and lipid content in the muscle increased with the dietary Se-Met level, and the total Se level in the whole body and muscle showed a linear increase with dietary Se-Met supplementation. Thermal stress changed the histology of the muscle, leading to raised levels of malondialdehyde (MDA), reduced antioxidant parameters in the serum and liver, and a decrease in the transcripts of selenoprotein genes in the muscle. Meanwhile, increased antioxidant capacity of serum and liver and up-regulated transcripts of selenoprotein of muscle were observed in L. maculatus reaching a maximum with 3.5 mg Se-Met/kg treatment. After 24 h of nitrite stress, thermal stress exacerbated oxidative damage caused by nitrite stress in L. maculatus. In contrast, dietary Se-Met enhanced the resistance to nitrite stress of L. maculatus fed with Se-Met enriched diets containing 0.9 to 1.8 mg Se-Met/kg. Based on the effects of dietary Se-Met on the growth, antioxidant capacity and resistance to nitrite stress of L. maculatus, this study suggests that the optimal range of Se-Met supplementation in L. maculatus diets is 1.80 to 2.39 mg Se-Met/kg of diet at 27 °C and 1.80 to 4.46 mg Se-Met/kg of diet at 33 °C.

中文翻译：

---

日粮中添加硒-L-蛋氨酸对两种饲养水温下斑点鲈鱼 （Lateolabrax maculatus） 生长、抗氧化能力和抗亚硝酸盐胁迫性的影响


进行了一项为期 10 周的喂养试验，然后进行 24 小时亚硝酸盐应激，以评估日粮硒-L-蛋氨酸 （Se-Met） 对生长、硒积累、抗氧化能力、硒蛋白转录和肌肉组织学变化的影响，以及在最佳 （27 °C） 和高温 （33 °C） 下饲养的斑点鲈鱼 （Lateolabrax maculatus） 对亚硝酸盐应激的抵抗力。将 5 种实验日粮配制为含有 0、0.9、1.8、3.5 和 7.0 mg Se-Met/kg。在 27 或 33 °C 的两次平行处理中，将每种日粮喂给鱼 （2.60 ± 0.2 g）。 结果表明，高温 （33 °C） 诱导鱼类热应激，与在 27 °C 下饲养的鱼类相比，热应激下的鱼类表现出较低的体重增加和肝体指数，但条件因子更高。 然而，0.9 至 3.5 mg/kg Se-Met 处理促进了黄斑乳杆菌 的生长和饲料利用。肌肉中蛋白质和脂质含量随膳食 Se-Met 水平的增加而增加，而膳食中添加 Se-Met 后，全身和肌肉中的总 Se 水平呈线性增加。热应激改变了肌肉的组织学，导致丙二醛 （MDA） 水平升高，血清和肝脏中的抗氧化参数降低，以及肌肉中硒蛋白基因转录物的减少。同时，在 3.5 mg Se-Met/kg 处理下，观察到 L. maculatus 血清和肝脏抗氧化能力增加以及肌肉硒蛋白转录物上调达到最大值。亚硝酸盐胁迫 24 h 后，热胁迫加剧了亚硝酸盐胁迫对黄斑乳 杆菌造成的氧化损伤。相比之下，膳食 Se-Met 增强了用富含 0.9 至 1.8 毫克 Se-Met/kg。根据膳食 Se-Met 对黄斑乳杆菌 生长、抗氧化能力和对亚硝酸盐胁迫的抵抗力的影响，本研究表明，黄斑乳杆菌 饮食中 Se-Met 补充剂的最佳范围是 27 °C 时 1.80 至 2.39 mg Se-Met/kg 饮食和 33 °C 时 1.80 至 4.46 mg Se-Met/kg 饮食。