A sustainable growth of the aquaculture sector implies the use of sustainable novel raw materials as replacers of the traditional fishmeal (FM) and fish oil (FO) ingredients. This fact has led to the development of sustainable and functional diets as part of a management strategy to reduce the effects on fish growth performance and health derived from low FM/FO dietary contents. In this sense, Antarctic krill (Euphausia superba) is considered a potential candidate in dietary inclusions to potentiate fish growth and health status. In this study, European sea bass (Dicentrarchus labrax) were fed a practical diet with either a 15% fishmeal content (KM0; control diet) or the same diet substituted by 30% (KM5; 5 g KM/kg diet) or 50% (KM7.5; 7.5 g KM/kg diet) Antarctic krill meal (KM) for 12 weeks in triplicates. At the end of the feeding trial, growth performance, liver morphology, liver proximate composition, lipid classes and fatty acid profiles, as well as the expression of hepatic genes related with lipid metabolism were evaluated. Fish fed KM-based diets presented higher (p < 0.05) final weight, protein and lipid efficiency ratios, specific growth rate (SGR) and improved feed conversion ratio (FCR), irrespective of the KM dietary level. Whole body and muscle proximate composition and fatty acid profiles were similar among dietary groups. Livers of European sea bass fed the experimental diets presented similar (p > 0.05) biochemical composition and fatty acid profile. However, smaller hepatocellular area and lower grade of cytoplasm vacuolization as well as a better alignment around sinusoidal spaces were found. The analyses of liver lipid classes revealed a positive correlation between the level of dietary KM and the pigmented material such as astaxanthin and free fatty acid content, as well as a negative correlation with the cholesterol levels. The expression of hepatic genes studied demonstrated a downregulation of 3-hydroxy-3-methylglutaryl-coenzyme A reductase (hmgr) and delta-6-desaturase (fads2) expression levels in fish fed KM-based diets. Besides, gene expression levels of fatty acid binding protein 7 (fabp7) and lipoprotein lipase (lpl) were significantly correlated with KM dietary levels. Altogether, these results profile KM as a potential promoter of growth and liver health in European sea bass fed low fish meal and oil diets.

水产养殖业的可持续增长意味着使用可持续的新型原材料作为传统鱼粉 (FM) 和鱼油 (FO) 成分的替代品。这一事实导致了可持续和功能性饮食的发展，作为管理策略的一部分，以减少低 FM/FO 饮食含量对鱼类生长性能和健康的影响。从这个意义上说，南极磷虾（Euphausia superba）被认为是一种潜在的膳食成分，可以促进鱼类的生长和健康状况。在这项研究中，欧洲鲈鱼（Dicentrarchus labrax) 喂食鱼粉含量为 15% 的实用日粮（KM0；对照日粮）或相同日粮用 30%（KM5；5 g KM/kg 日粮）或 50%（KM7.5；7.5 g KM/kg饮食）南极磷虾粉 (KM) 12 周，一式三份。在喂养试验结束时，评估了生长性能、肝脏形态、肝脏近似成分、脂质类别和脂肪酸谱，以及与脂质代谢相关的肝脏基因的表达。喂食以 KM 为基础的饮食的鱼表现出更高 ( p < 0.05) 最终重量、蛋白质和脂质效率比、比生长率 (SGR) 和改进的饲料转化率 (FCR)，与 KM 日粮水平无关。饮食组之间的全身和肌肉近似组成和脂肪酸谱相似。喂食实验饮食的欧洲鲈鱼肝脏表现出相似的 ( p > 0.05) 生化成分和脂肪酸谱。然而，发现较小的肝细胞面积和较低级别的细胞质空泡化以及在正弦空间周围更好的对齐。肝脏脂质类别的分析揭示了膳食 KM 水平与有色物质（如虾青素和游离脂肪酸含量）之间的正相关，以及与胆固醇水平的负相关。研究的肝脏基因的表达表明，在以 KM 为基础的饮食喂养的鱼中，3-羟基-3-甲基戊二酰辅酶 A 还原酶(hmgr)和 delta-6-去饱和酶 ( fads2 ) 的表达水平下调。此外，脂肪酸结合蛋白 7（fabp7) 和脂蛋白脂肪酶 ( lpl ) 与 KM 饮食水平显着相关。总而言之，这些结果将 KM 描述为低鱼粉和低油饮食的欧洲鲈鱼生长和肝脏健康的潜在促进剂。