本研究旨在确定日粮锌对幼年大嘴鲈鱼(Micropterussalmoides)生长和健康状况的影响。6种实验日粮,Zn水平分别为50.17、56.74、73.34、86.03、123.94和209.20mg/kg,分别使用复合氨基酸螯合锌复合,并饲喂幼鱼(5.50±0.10g)70d。特定生长速率(SGR)在二次模型中随饲料锌水平的变化而变化,并在73.34mg/kg组达到峰值,而摄食率表现出相反的趋势(P<0.05)。条件因素,肝体指数和肠系膜脂肪指数均表现出与SGR相似的趋势(P<0.05)。日粮锌水平影响血清总蛋白,尿素,甘油三酯,和葡萄糖(P<0.05)。血清锌和铜水平随饲料锌水平线性增加,而血清铁和锰表现出相反的趋势。血清超氧化物歧化酶(SOD)和总抗氧化能力(T-AOC)随着饲粮锌水平的增加而增加,在86.03mg/kg时达到平台状态。血清补体成分3(C3),IgM,溶菌酶也增加了73.34mg/kgZn。身体蛋白质含量随着锌水平的增加而增加,达到73.34mg/kg,然后保持稳定。随着日粮锌水平的增加,肝脏脂质水平升高,然后在86.03mg/kg组达到平台,而糖原线性增加。此外,来自肝脏转录组的与脂质和糖原代谢相关的基因表达进一步解释了肝脏脂质和糖原的变异。最后,建议幼年大口鲈鱼的膳食锌需求为76.99mg/kg,以改善生长,抗氧化能力,和免疫状态。
This study was conducted to ascertain the effect of dietary Zn on growth and health status of juvenile largemouth bass (Micropterus salmoides). Six experimental diets with Zn level of 50.17, 56.74, 73.34, 86.03, 123.94, and 209.20 mg/kg, respectively were compounded using complex amino acid-chelated zinc, and were fed to juvenile fish (5.50 ± 0.10 g) for 70 d. The specific growth rate (SGR) varied with dietary Zn level in a quadratic model and peaked at the 73.34 mg/kg group, while the feeding rate exhibited an opposite trend (P < 0.05). The condition factor, hepatosomatic index and mesenteric fat index all exhibited a tendency similar with SGR (P < 0.05). Dietary Zn level affected serum total proteins, urea, triglycerides, and glucose (P < 0.05). Serum Zn and copper levels linearly increased with dietary Zn level, while serum iron and manganese showed the opposite trend. Serum superoxide dismutase (SOD) and total antioxidant capacity (T-AOC) increased with dietary Zn level and reached a plateau at 86.03 mg/kg. Serum complement component 3 (C3), IgM, and lysozyme also were enhanced by 73.34 mg/kg Zn. Body protein content increased with zinc level up to 73.34 mg/kg, and then remained steadily. As dietary Zn level increased, hepatic lipid level increased and then reached a plateau at 86.03 mg/kg group, while glycogen increased linearly. Moreover, gene expression related to lipid and glycogen metabolism from liver transcriptome further explained the liver lipid and glycogen variations. To conclude, a dietary Zn requirement of 76.99 mg/kg was suggested for juvenile largemouth bass to improve growth, antioxidant capacity, and immune status.