The use of essential oils (EO's) as feed additive has been explored as tool to improve fish growth and health. The aim of this study was to evaluate the oregano essential oil (OEO) (Origanum vulgare) dietary supplementation for the catfish Lophiosilurus alexandri. Four diets supplemented with different OEO levels (0.0, 1.0, 2.0 and 4.0 g kg⁻¹) were evaluated in a feed trial conducted with fish of 15.7 ± 1.8 g and 9.5 ± 0.45 cm for 13 weeks. Were evaluated growth performance, biochemical parameters, intestinal histomorphometry, whole-body composition and muscle growth. Polynomial analysis showed that weight gain, length gain and specific growth rate were improved in fish fed with OEO supplemented diets, being 2.37, 2.56 and 2.33 g kg⁻¹ the respective levels that maximize these variables. Plasma glucose, cholesterol, triglycerides, LDL and HDL increased with OEO levels between 1.80–2.47 g kg⁻¹. Intestinal histomorphometry was not affected by OEO. Body protein content and hyperplasic muscle fibres were maximized with 2.10 and 2.25 g kg⁻¹ OEO, respectively. Body moisture, total lipids, ash and hypertrophic muscle fibres were not affected by OEO. In conclusion, dietary supplementation with 2.10–2.56 g kg⁻¹ OEO improves growth performance, body protein retention and muscle growth of L. alexandri.

中文翻译：

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牛至精油（Origanum vulgare）膳食补充剂改善了新热带鲶鱼 Lophiosilurus alexandri 的生长性能、身体蛋白质保留和肌肉增生

已探索使用精油 (EO's) 作为饲料添加剂作为改善鱼类生长和健康的工具。本研究的目的是评估用于鲶鱼Lophiosilurus alexandri的牛至精油 (OEO)（Origanum vulgare）膳食补充剂。在用 15.7 ± 1.8 g 和 9.5 ± 0.45 cm 的鱼进行 13 周的饲料试验中评估了四种添加不同 OEO 水平（0.0、1.0、2.0 和 4.0 g kg ^-1）的饮食。评估了生长性能、生化参数、肠道组织形态测定、全身成分和肌肉生长。多项式分析表明，饲喂 OEO 补充日粮的鱼的体重增加、长度增加和比生长率提高，分别为 2.37、2.56 和 2.33 g kg ^-1使这些变量最大化的相应水平。血浆葡萄糖、胆固醇、甘油三酯、低密度脂蛋白和高密度脂蛋白随着 OEO 水平在 1.80-2.47 g kg ^-1之间增加。肠道组织形态计量学不受 OEO 的影响。分别使用 2.10 和 2.25 g kg ^-1 OEO使身体蛋白质含量和增生的肌肉纤维最大化。身体水分、总脂质、灰分和肥大的肌肉纤维不受 OEO 的影响。总之，膳食补充剂中添加 2.10–2.56 g kg ^-1 OEO 可改善L 的生长性能、身体蛋白质保留和肌肉生长。 alexandri。