维生素E对日本沼虾生长性能、抗氧化性能及抗氨氮胁迫能力的影响

本试验旨在研究饲料中维生素E水平对日本沼虾(Macrobrachium nipponense)幼虾生长性能、抗氧化性能和抗氨氮胁迫能力的影响。选择健壮、平均初始体重为(0.119±0.004)g的900只日本沼虾幼虾,随机分为6个组,每组3个重复,每个重复50只。以维生素E乙酯为添加形式,配制6组维生素E实际含量分别为18.31、37.94、66.07、120.25、212.68和388.96 mg/kg的半纯化饲料(分别记为VE1、VE2、VE3、VE4、VE5和VE6组),饲喂8周,随后进行24 h氨氮胁迫试验。结果显示:1)各组日本沼虾成活率(SR)无显著差异(P0.05);随饲料维生素E水平的增加,日本沼虾增重率(WGR)呈先增加后下降的变化趋势,VE4组最高,且显著高于VE1组(P0.05);饲料系数(FCR)变化趋势则与WGR相反,VE4组最低,且显著低于VE1组(P0.05)。2)氨氮胁迫前,各组日本沼虾肝胰腺中丙二醛(MDA)含量随饲料维生素E水平的增加呈先下降后上升的变化趋势,在VE3组达到最低,且显著低于VE1、VE5和VE6组(P0.05);各组日本沼虾肝胰腺总超氧化物歧化酶(SOD)、过氧化氢酶(CAT)、谷胱甘肽过氧化物酶(GSH-Px)活力和总抗氧化力(T-AOC)随饲料维生素E水平的增加呈先上升后下降的变化趋势。VE1和VE6组日本沼虾硫氧还蛋白(Trx)mRNA表达量较高,硫氧还蛋白还原酶(TrxR)mRNA表达量则较低。VE3组热休克蛋白60(HSP60)mRNA表达量显著低于其他各组(P0.05),VE1组热休克同源蛋白70(HSC70)mRNA表达量显著低于其他各组(P0.05),VE1和VE2组热休克蛋白90(HSP90)mRNA表达显著高于其他各组(P0.05)。3)氨氮胁迫后,各组日本沼虾肝胰腺SOD、CAT、GSH-Px活力,MDA含量,Trx、TrxR和HSC70 mRNA表达量的变化趋势与胁迫前相似,HSP60和HSP90 mRNA表达量变化与胁迫前相反。氨氮胁迫可降低日本沼虾肝胰腺GSH-Px活力、T-AOC及Trx、TrxR mRNA表达量,提高MDA含量及VE4、VE5和VE6组SOD活力。由此可见,饲料中添加120.25 mg/kg维生素E对日本沼虾的生长具有积极的促进作用,饲料中添加66.07、120.25和212.68 mg/kg的维生素E可提高日本沼虾抗氧化性能和抗氨氮胁迫能力。

Effects of Dietary Vitamin E on Growth Performance,Antioxidant Ability and Resistance to Ammonia Nitrogen Stress of Macrobrachium nipponense

The present experiment was conducted to evaluate the effects of dietary vitamin E level on growth performance, antioxidant ability and resistance to ammonia nitrogen stress of juvenile Macrobrachium nippon-ense. A total of 900 healthy juvenile Macrobrachium nipponense with the body weight of (0.119±0.004) g were selected and randomly divided into 6 groups with 3 replicates per group and 50 shrimps per replicate. Vita-min E acetate was added to basal semi-purified diet at six levels to make diets with the actual content of 18.31, 37.94, 66.07, 120.25, 212.68 and 388.96 mg /kg vitamin E ( denoted by VE1, VE2, VE3, VE4, VE5 and VE6 groups, respectively) , and feeding for 8 weeks. After the feeding experiment, the prawns were subjected to ammonia nitrogen stress for 24 h. The results showed as follows:1) the survival rate of Macrobrachium nip-ponense in each group had no significant difference ( P>0.05) . The weight gain rate showed a trend of firstly increased and then decreased with the dietary vitamin E increasing, and prawns in VE4 group gained the high-est value and significantly higher than that in VE1 group ( P<0.05) . The feed conversion rate had the opposite pattern from the weight gain rate, the lowest value were found in VE4 group and significantly lower than that in VE1 group ( P<0.05) . 2) Before ammonia nitrogen stress, the maleic dialdehyde ( MDA) content in hepato-pancreas exhibited a trend of firstly decreased and then increased with dietary vitamin E increasing, the lowest value was found in VE3 group and significantly lower than that in VE1, VE5 and VE6 groups (P<0.05), whereas the activities of superoxide dismutase ( SOD ) , glutathione peroxidase ( GSH-Px ) , catalase ( CAT ) and total antioxidant competence ( T-AOC) in hepatopancreas exhibited a trend of firstly increased and then de-creased with dietary vitamin E increasing. VE1 and VE6 groups gained the higher thioredoxin ( Trx) mRNA expression and the lower thioredoxin reductase ( TrxR ) mRNA expression. The heat shock protein 60 (HSP60) mRNA expression in VE3 group was significantly lower than that in other groups (P<0.05), the heat shock cognate 70 ( HSC70 ) mRNA expression in VE1 group was significantly lower than that in other groups ( P<0.05) , the heat shock protein 90 ( HSP90) mRNA expression in VE1 and VE2 group was signifi-cantly higher than that in other groups (P<0.05). 3) After ammonia nitrogen stress, the SOD, CAT and GSH-Px activities, MDA content and the mRNA expressions of Trx, TrxR and HSC70 of Macrobrachium nip-ponense in each group had the similar pattern with the before stress, but the mRNA expressions of HSP90 and HSP60 exhibited an opposite trend with the before stress. Ammonia nitrogen stress decreased the GSH-Px activ-ities and T-AOC and the mRNA expressions of Trx and TrxR, increased MDA content and SOD activity of VE4, VE5 and VE6 groups. In conclusion, the results demonstrate that 120.25 mg/kg of dietary vitamin E in-crease the growth of Macrobrachium nipponense, 66.06, 120.25 and 212.68 mg/kg of dietary vitamin E en-hance antioxidant activity and alleviated the toxicity of ammonia nitrogen stress of Macrobrachium nipponense.