黄颡鱼幼鱼对饲料中维生素C的需要量

Dietary Vitamin C Requirement of Juvenile YellowCatfish( Pelteobagrus fulvidraco Rich)

以维生素C水平分别为1.9、18.9、36.8、78.4、156.5和316.0 mg/kg的6种等氮等脂饲料(含42%粗蛋白质和7%粗脂肪)投喂黄颡鱼(Pelteobagrus fulvidraco)幼鱼[初始体重(2.00±0.01)g]12周,研究饲料中维生素C水平对黄颡鱼幼鱼生长性能、抗氧化能力和免疫功能的影响。每种饲料设3个重复,每个重复放养20尾鱼。结果表明:1)当饲料中维生素C水平从1.9 mg/kg上升到156.5 mg/kg,增重率和特定生长率显著提高(P<0.05),然而随着饲料中维生素C水平由156.5 mg/kg上升到316.0 mg/kg,黄颡鱼幼鱼的增重率和特定生长率反而有所下降。饲料中维生素C水平对存活率、饲料系数、蛋白质效率、肝体比和脏体比的影响不显著(P>0.05)。2)饲料中维生素C水平对黄颡鱼幼鱼血液中血红蛋白含量和血清中葡萄糖、甘油三酯含量的影响显著(P<0.05),而血液中红细胞数量、白细胞数量、红细胞压积及血清中总蛋白和胆固醇含量不受饲料中维生素C水平的显著影响(P>0.05)。3)当饲料中维生素C水平由1.9 mg/kg上升到156.5 mg/kg时,血清中超氧化物歧化酶、过氧化氢酶和谷胱甘肽过氧化物酶的活性显著提高(P<0.05),丙二醛含量显著下降(P<0.05);当饲料中维生素C水平由156.5 mg/kg上升到316.0 mg/kg时,血清中超氧化物歧化酶、过氧化氢酶活性和丙二醛含量变化不显著(P>0.05),但谷胱甘肽过氧化物酶活性出现显著下降(P<0.05)。4)饲料中维生素C水平由1.9 mg/kg上升到156.5 mg/kg时,血清溶菌酶活性显著提高(P<0.05),但随着维生素C水平的继续升高,溶菌酶活性变化不显著(P>0.05)。随着饲料中维生素C水平的升高,头肾巨噬细胞吞噬百分率和呼吸爆发呈先上升后下降趋势,在维生素C水平为156.5 mg/kg时达到最大值。5)注射嗜水气单胞菌14 d后,饲料中维生素C水平为18.89和36.76 mg/kg时的累计存活率显著高于维生素C水平为1.9 mg/kg时(P<0.05)。以特定生长率和血清中溶菌酶活性为评价指标,通过折线模型得出黄颡鱼幼鱼饲料中维生素C的需要量分别为114.5和142.3 mg/kg。

A 12-week feeding trial was conducted to evaluate the effects of dietary vitamin C level on growth performance,antioxidant capacity and immune function of juvenile yellowcatfish（ Pelteobagrus fulvidraco Rich）. Six isonitrogenous and isolipidic diets（ 44 % crude protein and 7 % crude lipid） were formulated to contain six graded dietary vitamin C levels of 1. 9,18. 9,36. 8,78. 4,156. 5 and 316. 0 mg / kg diet. Each diet was randomly assigned to three replicates,and ecah replicate had 20 juvenile fish [average body weight of（ 2. 00±0. 01） g]. The results showed as follows： 1） the weight gain rate（ WGR） and specific growth rate（ SGR） were significantly increased when dietary vitamin C level increased from 1. 9 mg /kg to 156. 5 mg /kg（ P〈0. 05）,but then were decreased when dietary vitamin C level increased from 156. 5 mg /kg to316. 0 mg / kg. However,survival rate（ SR）,protein efficiency ratio（ PER）,feed efficiency（ FE）,hepatosomatic index（ HSI） and viscerosomatic index（ VSI） were not significantly affected by the dietary vitamin C level（ P〉0. 05）. 2） The dietary vitamin C level had significant effects on blood hemoglobin content and serum glucose and triglyceride contents（ P〈0. 05）,but had no significant effects on red blood cell count（ RBC）,white blood cell count（ WBC） and hematocrit in blood and total protein（ TP） and cholesterol（ CHOL） contents in serum（ P〉0. 05）. 3） The activities of serum superoxide dismutase（ SOD）,catalase（ CAT） and glutathione peroxidase（ GSH-Px） were significantly increased and the content of serum malondialdehyde（ MDA） was significantly decreased when dietary vitamin C level increased from 1. 9 mg / kg to 156. 5mg / kg（ P〈0. 05）; however,when dietary vitamin C level increased from 156. 5 mg / kg to 316. 0 mg / kg,the serum SOD and CAT activities and MDA content were not significant different（ P〉0. 05）,but the serum GSH-Px activity was significantly decreased（ P〈0. 05）. 4） The activity of serum lysozyme（ LZM） was significantly increased when dietary vitamin C level increased from 1. 9 mg / kg to 156. 5 mg / kg（ P〈0. 05）,but it had no significant change when dietary vitamin C level continued to increase（ P〉0. 05）. The phagocytic percentage and respiratory burst of macrophages from head kidney were firstly increased and then decreased with dietary vitamin C level increasing,and the highest values of them were appeared when dietary vitamin C level was 156. 5 mg / kg. 5） After injecting A. hydrophila for 14 days,the cumulative survival rate of 18. 89 and 36. 76 mg / kg groups was significantly higher than that of 1. 9 mg / kg group（ P〈0. 05）. Using SGR and serum LZMactivity as evaluation indexes,broken-line regression analysis results indicate that the dietary vitamin C requirement of juvenile yellowcatfish is estimated to be 114. 5 and 142. 3 mg / kg,respectively.