Abstract The objective of this study was to evaluate the use of soybean oil (SO) and two microalgal meals derived from Schizochytrium limacinum (SL1 and SL2) to replace fish oil (FO) in diets for Totoaba macdonaldi juveniles. Nine isoproteic (54% crude protein, CP) and isolipidic (14% crude fat, CF) diets were formulated based on a 3 × 3 factorial design, using the three lipid sources and three replacement levels, 33%, 66% and 100%. A control diet containing FO as the main lipid source served as a reference. Diets were fed for 6 weeks and were randomly assigned to six replicate tanks of a recirculating aquaculture system, with 25 fish stocked per tank. Initial mean fish weight was 8.08 g; at the end of the trial, statistical differences for growth responses such as weight gain (WG; P = 0.0069) and thermal growth coefficient (TGC; P = 0.0027) were detected. WG (SL1 = 50.75 g, SL2 = 51.43 g) and TGC (0.148) of fish fed the S. limacinum meals were significantly higher than in those fed SO (WG = 41.13 g; TGC = 0.129). Conversely, the hepatosomatic index (HSI; P = 0.0009) of fish fed SO was significantly higher (1.38%) compared to those fed the microalgae meals (SL1 = 1.13%, SL2 = 1.22%). Also, proximate composition of liver was significantly influenced by the lipid source and CF was significantly higher (P = 0.0067) in fish fed SO (47.68%) than in fish fed SL1 (37.44%) or SL2 (39.86%). The fatty acid (FA) profile of muscle and liver reflected the dietary FA composition; SO prompted increased concentrations of 18:2n-6 and total n-6 FA in fish fillet; whereas, the S. limacinum meals increased 22:6n-3, total n-3 FA and the n-3/n-6 ratios, which is highly desirable in food destined for human consumption. In addition, the concentration of pancreatic lipase 1 (70.2 kDa) in anterior intestine and pyloric caeca of fish significantly decreased (P = 0.0019) from 2.93 to 1.85 mg g−1 as the level of FO replaced increased. These findings indicate that up to 100% of FO can be replaced by S. limacinum meals improving the growth of T. macdonaldi and preserving the nutritional value and the health benefits of the fillet for human consumption; whereas, SO decreased growth and the concentration of 22:6n-3, 20:5n-3, total n-3, and n-3/n-6 ratios, while increasing the HSI and the risk of hepatic dysfunction and steatosis.

中文翻译：

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在 Totoaba macdonaldi (Gilbert, 1890) 幼鱼的饮食中用豆油和微藻粉替代鱼油

摘要 本研究的目的是评估使用豆油 (SO) 和两种源自 Schizochytrium limacinum (SL1 和 SL2) 的微藻粉替代鱼油 (FO) 在 Totoaba macdonaldi 幼鱼的饮食中的应用。基于 3 × 3 析因设计，使用三种脂质来源和三个替代水平（33%、66% 和 100%）配制了九种异蛋白（54% 粗蛋白，CP）和异脂（14% 粗脂肪，CF）日粮. 含有 FO 作为主要脂质来源的对照饮食作为参考。饲料喂养 6 周，并随机分配到循环水产养殖系统的六个重复池中，每个池放养 25 条鱼。初始平均鱼重为 8.08 克；在试验结束时，生长反应的统计差异，例如体重增加（WG；P = 0.0069）和热生长系数（TGC；P = 0. 0027) 被检测到。喂食 S. limacinum 饲料的鱼的 WG (SL1 = 50.75 g, SL2 = 51.43 g) 和 TGC (0.148) 显着高于喂食 SO (WG = 41.13 g; TGC = 0.129) 的鱼。相反，与喂食微藻粉的鱼（SL1 = 1.13%，SL2 = 1.22%）相比，喂食 SO 的鱼的肝体指数（HSI；P = 0.0009）显着更高（1.38%）。此外，肝脏的近似成分受脂质来源的显着影响，饲喂 SO (47.68%) 的鱼的 CF 显着高于饲喂 SL1 (37.44%) 或 SL2 (39.86%) 的鱼 (P = 0.0067)。肌肉和肝脏的脂肪酸 (FA) 分布反映了膳食 FA 组成；SO 促使鱼片中 18:2n-6 和总 n-6 FA 的浓度增加；而 S. limacinum 膳食增加了 22:6n-3、总 n-3 FA 和 n-3/n-6 比率，这在供人类食用的食物中是非常理想的。此外，随着 FO 水平的增加，鱼的前肠和幽门盲囊中胰脂肪酶 1 (70.2 kDa) 的浓度从 2.93 显着降低 (P = 0.0019) 至 1.85 mg g-1。这些发现表明，多达 100% 的 FO 可以被 S. limacinum 膳食替代，从而改善 T. macdonaldi 的生长并保持鱼片供人类食用的营养价值和健康益处；然而，SO 降低了生长和 22:6n-3、20:5n-3、总 n-3 和 n-3/n-6 比率的浓度，同时增加了 HSI 和肝功能障碍和脂肪变性的风险。93 至 1.85 mg g-1 随着 FO 水平的增加而增加。这些发现表明，多达 100% 的 FO 可以被 S. limacinum 膳食替代，从而改善 T. macdonaldi 的生长并保持鱼片供人类食用的营养价值和健康益处；然而，SO 降低了生长和 22:6n-3、20:5n-3、总 n-3 和 n-3/n-6 比率的浓度，同时增加了 HSI 和肝功能障碍和脂肪变性的风险。93 至 1.85 mg g-1 随着 FO 水平的增加而增加。这些发现表明，多达 100% 的 FO 可以被 S. limacinum 膳食替代，从而改善 T. macdonaldi 的生长并保持鱼片供人类食用的营养价值和健康益处；然而，SO 降低了生长和 22:6n-3、20:5n-3、总 n-3 和 n-3/n-6 比率的浓度，同时增加了 HSI 和肝功能障碍和脂肪变性的风险。