饲料精氨酸水平对斜带石斑鱼蛋白质沉积和相关免疫基因表达的影响

为研究饲料中不同水平精氨酸对斜带石斑鱼蛋白质沉积和相关免疫基因表达的影响,实验配制7种等氮等脂的饲料,精氨酸浓度分别为2.13%、2.42%、2.71%、2.95%、3.20%、3.48%和3.74%。随机挑选健康的斜带石斑鱼初始体质量(80.11±0.03) g]分成7组,每组设3个重复,每个重复25尾鱼,进行为期10周的养殖实验。结果显示,精氨酸浓度为2.71%组鱼体增重率和特定生长率显著高于2.13%和2.42%组,饲料系数显著低于2.13%组。2.71%组的蛋白质效率显著高于2.13%组和3.48%组,2.71%组的蛋白质沉积率与2.95%组无显著差异,显著大于其他组。以增重率为依据,经折线模型拟合得出,斜带石斑鱼对饲料中精氨酸的最适需求量为饲料的2.73%(饲料蛋白质的5.40%)。斜带石斑鱼血清胰岛素在3.20%组达到最大值,与3.48%组差异不显著,显著高于其他组。肌肉雷帕霉素靶蛋白(TOR) mRNA水平3.48%组显著高于2.13%、2.42%及2.71%组。2.42%组后肠b0,+AT基因表达量最高,显著高于其他各组。2.95%和3.20%组肾脏b~(0,+)AT基因表达量差异不显著,显著高于其他组。研究表明,适宜水平的饲料精氨酸可以刺激斜带石斑鱼胰岛素生长因子-Ⅰ(IGF-Ⅰ)的分泌,进而促进蛋白质的合成;提高鱼体肠道、肾脏及肝脏相关免疫基因的表达,提高机体免疫力,促进鱼体生长。

Effects of dietary arginine levels on protein deposition and related immune gene expression in Epinephelus coioides

A 10-week feeding trial was conducted to investigate the effects of dietary arginine levels on the growth performance and immunity of Epinephelus coioides. Seven isonitrogenous and isolipid diets were formulated with arginine contents of 2.13%, 2.42%, 2.71%, 2.95%, 3.20%, 3.48% and 3.74% (dry matter) respectively. Randomly selected healthy groupersinitial weight (80.11±0.03) g] were divided into 7 groups, with 3 replicates in each group and 25 fish per replicate. It was found that the weight gain rate (WGR) and specific growth rate (SGR) of 2.71% group were significantly higher than 2.13% and 2.42% groups, and the feed coefficient (FCR) was significantly lower than that 2.13% group. The protein efficiency rate of the 2.71% group was significantly higher than those of 2.13% and 3.48% groups, and the protein deposition rate of the 2.71% group was not significantly different from that of 2.95% group, which was significantly higher than that of other groups. Broken-line model analysis of weight growth rate against dietary arginine levels indicated that the optimum requirement of arginine for maximum growth of subadult grouper was 2.73%, corresponding to 5.40% of dietary protein on a dry weight basis. There was no significant difference between 3.20% serum insulin (INS) and 3.48% groups, which were significantly higher than other groups. The level of TOR gene in muscle of 3.48% group was significantly higher than those of 2.13%, 2.42% and 2.71% groups. The expression of b^0,+ AT gene in the hindgut of 2.42% group was the highest, which was significantly higher than that of other groups. There was no significant difference in the expression of b^0,+ AT gene of kidney between 2.95% and 3.20% groups, which was significantly higher than that of other groups. In conclusion, the appropriate level of feed arginine can stimulate the secretion of IGF-I of E. coioides to promote the synthesis of protein and improve the expression of immune genes of the intestine, kidney and liver of fish to improve the body immunity, and ultimately promote the growth of fish.