The current study aimed to assess the citric acid (CA) and soybean meal (SBM) and blend them (3 × 3 factorial trials) on rainbow trout (Oncorhynchus mykiss). Treatment groups contain three levels of SBM levels (0, 350, and 750 g/kg) to replace dietary fish meal, each of which was supplemented with 0, 10 and 20 g/kg CA. Triplicate groups of 20 fish (7.84 ± 0.32 g) in 27 tanks were fed their related diets for 60 days. The highest weight gain, specific growth rate, protein efficiency ratio, and the lowest feed conversion ratio were recorded in the group, fed a diet blended with CA 20 g/kg and free of SBM (p < .05). The overall survival rate elevated with CA supplementation in the diet (p < .05). There were no significant differences (p > .05) among dietary CA and SBM levels with respect to body composition, haematological and biochemical indices except for glucose. The highest and lowest values of C22:6n-3 and highly unsaturated fatty acid were observed in group fed diet-free level and high level of soybean meal. CA supplementation had improved the apparent digestibility coefficients for SBM-based diets, including protein and phosphorus. Taken together, these results suggested that incremental levels of CA supplementation in an SBM-based diet could improve the use of them.

中文翻译：

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同时食用柠檬酸和大豆基饲料对虹鳟鱼幼鱼生长性能、身体成分、血液生化指标、消化率和脂肪酸组成的影响

目前的研究旨在评估柠檬酸 (CA) 和豆粕 (SBM) 并将它们混合（3 × 3 析因试验）用于虹鳟鱼 ( Oncorhynchus mykiss )。处理组包含三个水平的 SBM 水平（0、350 和 750 g/kg）来代替膳食鱼粉，每个鱼粉补充 0、10 和 20 g/kg CA。将 27 个鱼缸中的 20 条鱼（7.84 ± 0.32 克）一式三份，用它们的相关饮食喂养 60 天。该组记录了最高的增重、特定生长率、蛋白质效率比和最低的饲料转化率，饲喂与 CA 20 g/kg 混合且不含 SBM 的日粮 ( p  < .05)。在饮食中添加 CA 可提高总存活率 ( p  < .05)。无显着差异（p > .05) 在饮食 CA 和 SBM 水平之间，除了葡萄糖外，身体成分、血液学和生化指标。C22:6n-3和高度不饱和脂肪酸的最高值和最低值分别出现在无日粮饲喂水平和豆粕饲喂水平较高的组中。CA 的补充改善了基于 SBM 的饮食的表观消化率系数，包括蛋白质和磷。总之，这些结果表明在基于 SBM 的饮食中增加 CA 补充水平可以改善它们的使用。