This study examined the effects of feeding largemouth bass (Micropterus salmoides) with diets containing different doses of astaxanthin (0, 50, 100, 150, and 200 mg/kg) for 8 weeks. The results showed that the values of weight gain significantly increased from 620.32 ± 50.38% to 826.14 ± 33.49% as dietary astaxanthin levels increased from 0 mg/kg to 100 mg/kg. When the astaxanthin level exceeded 150mg/kg, the weight gain rate showed a downward trend, but there was no significant difference among of the 100, 150 and 200 mg/kg groups. The feed conversion ratio (FCR) and protein efficiency ratio (PER) were also improved by adding astaxanthin to diets (P < 0.05). Meanwhile, adding astaxanthin to the feed increased the length and thickness of intestinal villus and muscle layer thickness (P < 0.05). The astaxanthin supplementation increased the expression of the NF-E2-related factor (Nrf2) gene and reduced malondialdehyde (MDA) content and the expression of apoptosis genes Caspase-9 and Caspase-3 (P < 0.05), indicating that it has a good antioxidant ability. Furthermore, adding astaxanthin increased the content of non-specific immune markers and decreased the expression levels of the inflammatory factors interleukin-15 (IL-15) and tumor necrosis factor-α (TNF-α). Moreover, fish fed diets with astaxanthin exhibited lower blood cortisol levels (P < 0.05). The proportions of C20:4n6 (ARA) and C20:5n3 (EPA) in the liver decreased with increasing dietary astaxanthin levels. Based on WGR and SGR values, the optimal addition level of astaxanthin in largemouth bass feed is 134.8 mg/kg ~ 135.75 mg/kg. In summary, the appropriate dietary astaxanthin enhanced the antioxidant capacity and immune response of largemouth bass and had a positive effect on its intestinal health.

中文翻译：

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膳食虾青素对大口黑鲈生长性能、免疫力和组织成分的影响


本研究检验了用含有不同剂量虾青素（0、50、100、150 和 200 毫克/千克）的饲料喂养大口黑鲈 (Micropterus salmoides) 8 周的效果。结果表明，随着膳食虾青素水平从0mg/kg增加到100mg/kg，体重增加值从620.32±50.38%显着增加到826.14±33.49%。当虾青素水平超过150mg/kg时，增重率呈下降趋势，但100、150、200mg/kg组之间无显着差异。在日粮中添加虾青素也提高了饲料转化率（FCR）和蛋白质效率（PER）（P < 0.05）。同时，饲料中添加虾青素增加了肠绒毛的长度和厚度以及肌层厚度（P < 0.05）。补充虾青素增加了NF-E2相关因子（Nrf2）基因的表达，降低了丙二醛（MDA）含量以及凋亡基因Caspase-9和Caspase-3的表达（P < 0.05），表明其具有良好的抗氧化作用。抗氧化能力。此外，添加虾青素增加了非特异性免疫标志物的含量，并降低了炎症因子白细胞介素-15（IL-15）和肿瘤坏死因子-α（TNF-α）的表达水平。此外，喂食含有虾青素的鱼的血液皮质醇水平较低（P < 0.05）。肝脏中 C20:4n6 (ARA) 和 C20:5n3 (EPA) 的比例随着膳食虾青素水平的增加而降低。根据WGR和SGR值，大口黑鲈饲料中虾青素的最佳添加量为134.8 mg/kg ~ 135.75 mg/kg。综上所述，膳食中适量添加虾青素可增强大口黑鲈的抗氧化能力和免疫反应，对其肠道健康产生积极影响。