精氨酸对团头鲂幼鱼生长、血清游离精氨酸和赖氨酸、血液生化及免疫指标的影响

选用初始体质量为(2.60±0.10) g的团头鲂(Megalobrama amblycephala)幼鱼540尾, 随机分为6组, 每组3个重复, 每个重复30尾鱼, 分别投喂精氨酸水平(实测值)为0.83%、1.30%、1.81%、2.35%、2.82%和3.36%(占饲料的质量分数)的6组等氮等能半精制饲料, 饲养期为9周, 探讨精氨酸对团头鲂幼鱼生长、血清游离精氨酸和赖氨酸、血液生化及免疫指标的影响。实验结果表明, 随着饲料中精氨酸水平的增加, 团头鲂幼鱼增重率和饲料效率显著升高(P<0.05), 均在1.81%组达到最大; 随着精氨酸水平的进一步增加, 上述指标不再发生显著变化(P>0.05); 饲料中精氨酸水平对各组存活率无显著影响(P>0.05)。与对照组(0.83%)相比, 1.81%、2.82%和3.36%组团头鲂幼鱼血清中精氨酸含量显著提高(P<0.05), 3.36%组血清中赖氨酸含量却显著降低(P<0.05)。与对照组相比, 1.30%和1.81%组团头鲂幼鱼血清中谷草转氨酶活性显著降低(P<0.05), 1.81%、2.35%、2.82%和3.36%组血清中总蛋白和球蛋白的含量显著提高(P<0.05)。3.36%组团头鲂幼鱼血清中尿素含量显著高于其他各组 (P<0.05), 但饲料中精氨酸水平对各组血清中谷丙转氨酶活力、葡萄糖和白蛋白含量没有显著影响(P>0.05)。随着饲料中精氨酸水平的增加, 团头鲂幼鱼血液中白细胞、红细胞数量和血红蛋白含量都呈先上升后趋于平缓的趋势, 其中1.81%组最高; 饲料中精氨酸水平对血栓细胞数量无显著影响(P>0.05)。与对照组相比, 1.81%和2.35%组显著提高了血清中补体3的含量(P<0.05), 却对血清中补体4的含量无显著影响(P>0.05)。添加精氨酸显著(P<0.05)提高了血细胞呼吸爆发活性, 同时显著(P<0.05)降低了团头鲂幼鱼感染嗜水气单胞菌后累计死亡率。综上所述, 饲料中精氨酸含量为1.81%和2.35%时, 团头鲂幼鱼生长、氨基酸吸收以及鱼体的免疫力和抗病原菌感染能力均达到最高。

Effects of dietary arginine level on growth performance, free essential amino acids, hematological characteristics, and immune response in juvenile blunt snout bream (Megalobrama amblycephala)

We conducted a 9-week feeding trial to investigate the effect of dietary arginine on free essential amino acids, hematological characteristics, and the immune response in juvenile Megalobrama amblycephala. Six isonitrogenous and isoenergetic semi-purified diets were formulated to contain graded dietary arginine levels (actual levels: 0.83%, 1.30%, 1.81%, 2.35%, 2.82%, and 3.36%). The protein source consisted of casein-gelatin-fish meal and a crystalline amino acid mixture. The experimental fish (2.6±0.1 g) were randomly assigned among 18 cages (1 m×1 m×1 m, 30 ind/cage). Each experimental diet was fed to fish in triplicate tanks using a completely randomized design. Weight gain rate (WGR) and feed efficiency rate (FER) increased significantly with an initial increase in dietary arginine levels (P<0.05), but tended to plateau above a dietary arginine level of 1.81%. The crystalline arginine was used by juvenile snout bream, but there was a negative correlation between arginine and lysine content in the plasma. Dietary supplementation with arginine caused a significant increase in urea, total protein (TP) and globulin (GLB) concentrations (P<0.05), a decrease in plasma aspartate aminotransferase (AST) activity, and an invariable level difference in the plasma glucose (GLU) concentration, alanine aminotransferase (ALT) activity and albumin (ALB) in juvenile blunt snout bream, relative to the control diet (0.85%). Hemoglobin content (HGB) content, red blood cell (RBC) count, and white blood cell (WBC) count increased significantly (P<0.05) with an increase in dietary arginine level between 0.83% and 1.81%. However, there was a significant (P<0.05) decrease with an increase in dietary arginine levels between 2.35% and 3.36%. The maximum RBC count, WBC count, and HGB content were observed in animals fed 1.81% dietary arginine. Dietary arginine level significant affected the respiratory burst assay of blood cell (P<0.05), and had a negative effect on cumulative mortality in juvenile M. amblycephala infected with Aeromonas hydrophila. Our results suggests that feed supplementation with 1.81% and 2.35% arginine enhances amino acid absorption and stimulates immunity and resistance to pathogenic infection in juvenile M. amblycephala.