Abstract：
This study was conducted to investigate whether optimal vitamin C (VC) levels can enhance non-specific immune response and antioxidant capacity and reduce mortality of Pacific white shrimp (Penaeus vannamei) post-larvae when infected with Vibrio parahaemolyticus. Six experimental diets were formulated to contain six different VC levels of 0, 40, 80, 120, 160 and 320 mg/kg diet (designated as C0, C40, C80, C120, C160 and C320, respectively). Shrimp post-larvae (39.1 ± 0.47 mg) were randomly distributed to 24 tanks with 40 shrimp per tank. Four replicate groups of shrimp were fed one of the diets for 43 days. VC supplemented groups showed significantly higher growth performance than C0 group. Shrimp fed C120 diet had significantly improved feed utilization efficiency than shrimp fed C0 diet. VC concentrations in hepatopancreas and gills were significantly higher with the increase in dietary VC levels. Optimal dietary VC levels significantly upregulated the expressions of growth and digestive enzyme-related genes such as IGF-1, IGF-BP, amylase, trypsin and chymotrypsin, and also upregulated the expressions of innate immunity and antioxidant-related genes such as prophenoloxidase, crustin, penaiedin-3a, superoxide dismutase, glutathione peroxidase and catalase in hepatopancreas. Shrimp fed C80, C120 and C160 diets showed significantly increased resistance to V. parahaemolyticus than shrimp fed C0 diet. The optimum dietary VC level for the shrimp post-larvae was established to be 80.2 mg/kg diet by a broken-line regression analysis based on the growth. The findings from the challenge test indicated that VC levels over 83.0 mg/kg diet could enhance disease resistance of the shrimp against V. parahaemolyticus.
摘要：
进行这项研究以调查最佳维生素C（VC）水平是否可以增强非特异性免疫反应和抗氧化能力，并降低感染副溶血弧菌后的太平洋白虾（南美白对虾）的死亡率。将六种实验饮食配制成含有六种不同VC水平的0、40、80、120、160和320mg/kg饮食(分别指定为C0、C40、C80、C120、C160和C320)。将虾后幼虫（39.1±0.47mg）随机分配到24个罐中，每个罐40只虾。将四组重复的虾饲喂其中一种饮食43天。VC添加组表现出显著高于C0组的生长性能。饲喂C120日粮的虾比饲喂C0日粮的虾显著提高了饲料利用效率。肝胰腺和g中的VC浓度随着饮食VC水平的增加而显着升高。饲粮VC水平显著上调生长和消化酶相关基因如IGF-1、IGF-BP、淀粉酶，胰蛋白酶和胰凝乳蛋白酶,并上调先天免疫和抗氧化相关基因如酚氧化酶原的表达，Crustin,penaiedin-3a,超氧化物歧化酶,肝胰腺中的谷胱甘肽过氧化物酶和过氧化氢酶。饲喂C80，C120和C160日粮的虾比饲喂C0日粮的虾对副溶血性弧菌的抗性显着提高。通过基于生长的折线回归分析，对虾幼虫的最佳日粮VC水平确定为80.2mg/kg日粮。攻击试验的结果表明，VC水平超过83.0mg/kg饮食可以增强虾对副溶血性弧菌的抗病性。
