Nile Tilapia Oreochromis niloticus have a reported dietary requirement for the n‐6 C₁₈ polyunsaturated fatty acid (PUFA) 18:2n‐6 (linoleic acid), but direct provision of the n‐6 long‐chain (LC) PUFA 20:4n‐6 (arachidonic acid) may be a more efficient approach. No quantitative requirement for n‐3 fatty acids has been formally recognized for tilapias, but beneficial effects of having both n‐3 and n‐6 PUFAs in the diet have been reported. To better understand PUFA essentiality in tilapias, we formulated diets to assess the growth performance and tissue fatty acid composition of juvenile Nile Tilapia (mean ± SD = 25.7 ± 0.2 g/fish) that were fed different combinations of n‐3 and n‐6 PUFAs: a positive control containing menhaden fish oil, a negative control containing hydrogenated soybean oil, and experimental diets containing hydrogenated soybean oil amended with ethyl esters of 18:3n‐3; 18:3n‐3 and 18:2n‐6; 22:6n‐3; 22:6n‐3 and 20:4n‐6; or 20:5n‐3, 22:6n‐3, and 20:4n‐6. After 7 weeks, weight gain, feed conversion ratio, and specific growth rate were significantly greater among fish that received the positive control feed than among fish that were fed the negative control feed. The addition of n‐3 and n‐6 PUFA supplements generally improved performance in most cases. No fish showed any gross indications of fatty acid deficiency, although significant differences in fatty acid deficiency indicator ratios (i.e., 20:3n‐9 : 20:4n‐6 and 22:5n‐6 : 22:6n‐3) were present in all tissues analyzed. Nile Tilapia that were fed an n‐3 PUFA‐free diet exhibited significantly elevated 22:5n‐6 : 22:6n‐3 ratios, indicating a developing n‐3 PUFA deficiency. Feeding n‐3 PUFAs—as 18:3n‐3, 22:6n‐3, or a combination of n‐3 LC‐PUFAs—had a corrective effect on these ratios, affirming the importance of a proper balance of n‐3 and n‐6 PUFAs to satisfy the essential fatty acid requirements of Nile Tilapia and further illustrating the ability of this species to satisfy physiological demand for LC‐PUFAs through de novo biotransformation of C₁₈ PUFAs.

中文翻译：

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重新评估尼罗罗非鱼中多不饱和脂肪酸的必要性

据报道尼罗罗非鱼Oreochromis niloticus对n-6 C _18的饮食需求多不饱和脂肪酸（PUFA）18：2n-6（亚油酸），但是直接提供n-6长链（LC）PUFA 20：4n-6（花生四烯酸）可能是一种更有效的方法。罗非鱼尚未正式认识到对n-3脂肪酸的定量要求，但据报道在饮食中同时含有n-3和n-6 PUFA都有有益效果。为了更好地了解罗非鱼中PUFA的必要性，我们制定了日粮以评估饲喂n-3和n-6不同组合的尼罗罗非鱼幼鱼的生长性能和组织脂肪酸组成（平均±SD = 25.7±0.2 g /鱼）。 PUFAs：含有鱼腥草鱼油的阳性对照，含有氢化大豆油的阴性对照，以及含有氢化大豆油和18：3n-3乙酯修饰的实验饮食；18：3n-3和18：2n-6；22：6n-3; 22：6n-3和20：4n-6；或20：5n-3、22：6n-3和20：4n-6。7周后，接受阳性对照饲料的鱼的体重增加，饲料转化率和比生长速率显着高于接受阴性对照饲料的鱼。在大多数情况下，添加n-3和n-6 PUFA补充剂通常可以改善性能。尽管在鱼类中脂肪酸缺乏指标的比率存在显着差异（即20：3n-9：20：4n-6和22：5n-6：22：6n-3），但没有鱼类显示出任何脂肪酸缺乏的总体迹象。分析所有组织。饲喂无n-3 PUFA饮食的尼罗罗非鱼显示22：5n-6：22：6n-3比率显着升高，表明正在发展n-3 PUFA缺乏症。以18：3n-3、22：6n-3或n-3 LC-PUFA的组合的形式添加n-3 PUFA对这些比例具有校正作用，_18个PUFA。