饲料中胆固醇含量对淡水养殖凡纳滨对虾生长性能、抗弧菌和抗亚硝态氮胁迫能力的影响

为研究饲料中胆固醇含量对淡水养殖条件下凡纳滨对虾(Litopenaeus vannamei)生长性能、抗弧菌和抗亚硝态氮胁迫能力的影响,在10%鱼粉的基础上设计胆固醇添加量分别为0(C0组)、1(C1组)、2(C2组)、3(C3组)和4 g/kg(C4组)的等氮等能饲料(实测饲料中胆固醇含量依次为0.78、1.57、2.45、3.43和4.18 g/kg),分别投喂初始体重为(0.160±0.002)g的凡纳滨对虾50 d。每种饲料投喂4个网箱,每个网箱养殖凡纳滨对虾50尾。养殖试验结束后检测对虾的生长性能、肌肉常规组成以及急性哈维氏弧菌(Vibrio harveyi)感染及亚硝态氮胁迫下的死亡情况。结果表明:凡纳滨对虾的特定生长率和存活率不受饲料胆固醇含量的显著影响(P0.05),但C0组对虾的饲料系数显著高于C2、C3和C4组(P0.05)。随饲料胆固醇含量的增加,对虾肌肉中粗蛋白质含量逐渐升高,C3、C4组显著高于C0组(P0.05);肌肉中粗脂肪含量先升高后降低,C2组显著高于其他组(P0.05)。肝胰腺和肌肉中胆固醇含量随饲料胆固醇含量的增加而显著升高(P0.05),血清中胆固醇含量先升高后降低,且C2组显著高于C0组(P0.05)。急性感染哈维氏弧菌后,随饲料胆固醇含量的增加,同一时间点各组对虾累积死亡率均先降低后升高,C2组在感染24、36、48、72和96 h后的累积死亡率均最低。在8.5~9.0 mg/L亚硝态氮急性胁迫下,96 h后对虾累积死亡率与饲料中胆固醇含量呈负相关,且C0和C1组显著高于C2、C3和C4组(P0.05)。综上所述,淡水养殖条件下,1.57 g/kg的饲料胆固醇含量即可满足凡纳滨对虾生长的需求,但2.45 g/kg的饲料胆固醇含量可使对虾获得最佳的抗弧菌能力和理想的抗亚硝态氮胁迫能力。

Effects of Dietary Cholesterol Content on Growth Performance,Vibrio and Nitrite Nitrogen Stress Resistant Abilities of Litopenaeus vannamei Cultured in Freshwater

In order to assess the effects of dietary cholesterol content on the growth performance, Vibrio and nitrite nitrogen stress resistant abilities of Litopenaeus vannamei cultured in freshwater, five isonitrogenous and isoenergetic experimental diets were formulated based on 10% fish meal and supplemented 0 ( C0 group) , 1 ( C1 group) , 2 ( C2 group) , 3 ( C3 group) and 4 g/kg cholesterol( C4 group) , respectively, and those diets were fed to the Litopenaeus vannamei with the initial body weight of (0.160±0.002) g for 50 days. The meas?ured cholesterol content of experimental diets in C0, C1, C2, C3 and C4 groups were 0.78, 1.57, 2.45, 3.43 and 4.18 g/kg, respectively. Each diet fed four net?cages and each net?cage had 50 shrimps. After feeding ex?periment, the growth performance, proximate composition of muscle, and the survival condition after acute Vibrio harveyi infection and nitrite nitrogen stress were investigated. The results showed as follows:there were no significant differences in survival ratio and specific growth rate among groups (P>0.05), while the feed conversion rate (FCR) of C0 group was significantly higher than that of C2, C3 and C4 groups (P<0.05). The crude protein content in muscle of shrimps was increased along with the dietary cholesterol content rising, and that of C3 and C4 groups displayed significantly higher than that of C0 group ( P<0.05) . The crude lipid content in muscle of shrimps was firstly increased then decreased along with the dietary cholesterol content ris?ing, and that of C2 group was significantly higher than that of other groups ( P<0.05) . The cholesterol content in hepatopancreas and muscle of shrimps was significantly increased with the dietary cholesterol content rising ( P<0.05) , while the cholesterol content in serum was firstly increased then decreased, and that of C2 group was significantly higher than that of C0 group (P<0.05).When the shrimps were acute challenged with Vibrio harveyi, the cumulative mortality in the same time point was firstly decreased and then increased along with the dietary cholesterol content rising, and the C2 group always displayed the lowest cumulative mortality at 24, 36, 48, 72 and 96 h after infection. There was a negative correlation between the cumulative mortality at 96 h after stress and the dietary cholesterol content when the shrimps were stressed with 8.5 to 9.0 mg/L nitrate ni?trogen, and the cumulative mortality of C0 and C1 groups was significantly higher than that of other groups ( P<0.05) . It is suggested that the diet containing 1.57 g/kg cholesterol will satisfy the normal cholesterol re?quirement for growth of Litopenaeus vannamei cultured in freshwater, and the diet containing 2.45 g/kg cho?lesterol displays the strongest Vibrio resistant ability and the ideal nitrate nitrogen stress resistant ability.