Abstract：
Developing a low-protein feed is important for the sustainable advancement of aquaculture. The aim of this study was to investigate the effects of essential amino acid (EAA) supplementation in a low-protein diet on the growth, intestinal health, and microbiota of the juvenile blotched snakehead, Channa maculata in an 8-week trial conducted in a recirculating aquaculture system. Three isoenergetic diets were formulated to include a control group (48.66 % crude protein (CP), HP), a low protein group (42.54 % CP, LP), and a low protein supplementation EAA group (44.44 % CP, LP-AA). The results showed that significantly lower weight gain (WG), specific growth rate (SGR), protein efficiency ratio (PER), and feed efficiency ratio (FER) were observed in fish that were fed LP than in the HP and LP-AA groups (P < 0.05). The HP and LP-AA groups exhibited a significant increase in intestinal villus length, villus width, and muscular thickness compared to the LP group (P < 0.05). Additionally, the HP and LP-AA groups demonstrated significantly higher levels of intestinal total antioxidant capacity (T-AOC), catalase (CAT), and superoxide dismutase (SOD) and lower levels of malondialdehyde (MDA) compared to the LP group (P < 0.05). The apoptosis rate of intestinal cells in the LP group was significantly higher than those in the LP and HP groups (P < 0.05). The mRNA expression levels of superoxide dismutase (sod), nuclear factor kappa B p65 subunit (nfκb-p65), heat shock protein 70 (hsp70), and inhibitor of NF-κBα (iκba) in the intestine were significantly higher in the LP group than those in the HP and LP-AA groups (P < 0.05). The 16s RNA analysis indicated that EAA supplementation significantly increased the growth of Desulfovibrio and altered the intestinal microflora. The relative abundances of Firmicutes and Cyanobacteria were positively correlated with antioxidant parameters (CAT and T-AOC), whereas Desulfobacterota was negatively correlated with sod and T-AOC. The genera Bacillus, Bacteroides, and Rothia were associated with the favorable maintenance of gut health. In conclusion, dietary supplementation with EAAs to achieve a balanced amino acid profile could potentially reduce the dietary protein levels from 48.66 % to 44.44 % without adversely affecting the growth and intestinal health of juvenile blotched snakeheads.
摘要：
开发低蛋白饲料对于水产养殖的可持续发展至关重要。这项研究的目的是研究在低蛋白饮食中补充必需氨基酸（EAA）对生长的影响，肠道健康,和幼年斑驳的蛇头的微生物群，Channamaculata在循环水产养殖系统中进行的为期8周的试验。配制了三种等能量饮食，包括一个对照组(48.66%粗蛋白(CP)，HP),低蛋白组(42.54%CP，LP),和低蛋白补充EAA组(44.44%CP，LP-AA）。结果表明，显著降低增重(WG)，比增长率(SGR)，蛋白质效率比（PER），饲喂LP的鱼的饲料效率比（FER）高于HP和LP-AA组（P<0.05）。HP和LP-AA组肠绒毛长度显著增加,绒毛宽度,肌厚度与LP组比较(P<0.05)。此外,HP和LP-AA组显示出较高水平的肠道总抗氧化能力(T-AOC),过氧化氢酶(CAT),与LP组相比，超氧化物歧化酶（SOD）和丙二醛（MDA）水平降低（P<0.05）。LP组肠细胞凋亡率明显高于LP和HP组(P<0.05)。超氧化物歧化酶（sod）的mRNA表达水平，核因子κBp65亚基（nfκb-p65），热休克蛋白70（hsp70），LP组肠道NF-κBα抑制剂(iκba)明显高于HP组和LP-AA组(P<0.05)。16sRNA分析表明，补充EAA可显着增加Desulfovibrio的生长并改变肠道菌群。Firmicutes和蓝细菌的相对丰度与抗氧化参数（CAT和T-AOC）呈正相关，而脱硫杆菌与sod和T-AOC呈负相关。芽孢杆菌属,拟杆菌,和Rothia与肠道健康的良好维护有关。总之,饮食中补充EAA以实现平衡的氨基酸谱可能会将饮食中的蛋白质水平从48.66％降低到44.44％，而不会对幼鱼的生长和肠道健康产生不利影响。
