饲料铜水平对黄鳝生长、组织铜蓄积和血清生化指标的影响

Effects of Dietary Copper Level on Growth,Tissue Copper Accumulation and Serum Biochemical Indexes of Rice Field Eel(Monopterus albus)

本试验旨在探究黄鳝对饲料中铜的需求量及铜在黄鳝组织中的蓄积规律,为确定黄鳝配合饲料中铜水平和保障黄鳝食品安全提供依据。试验以五水硫酸铜为铜源,采用等对数间距的形式在基础饲粮中分别添加0、10.0、36.8、135.7、500.0 mg/kg的铜,实测饲料铜水平分别为14.21、23.95、37.01、135.63、499.63 mg/kg,在相同的养殖条件下投喂初重为(62.09±1.07)g黄鳝60 d后测定生长指标、形态参数、体成分、组织铜蓄积量和血清生化指标。每种饲料投喂4个养殖箱(重复),每个养殖箱投放30尾黄鳝。结果显示:随着饲料铜水平的升高,黄鳝的增重率、特定生长率均为先升高后降低,饲料系数则表现为先降低后升高,在饲料铜水平为37.01 mg/kg时,增重率、特定生长率及饲料系数均表现最佳。饲料铜水平对黄鳝全鱼、肝脏、肠道、脾脏及皮肤铜蓄积量有显著影响(P<0.05),而对肾脏和肌肉铜蓄积量无显著影响(P>0.05),且各组黄鳝肌肉铜蓄积量均维持在较低水平。黄鳝不同组织铜蓄积量表现为肝脏>肠道>脾脏>全鱼>皮肤,其中499.63 mg/kg铜组肝脏铜蓄积量超过国家食品中铜安全限量标准(50 mg/kg)。饲料铜水平对黄鳝血清谷草转氨酶(GOT)、碱性磷酸酶(AKP)及溶菌酶(LZM)活性无显著影响(P>0.05)。随着饲料铜水平的升高,黄鳝血清谷丙转氨酶(GPT)、铜锌超氧化物歧化酶(Cu-Zn SOD)活性和总抗氧化能力(T-AOC)先升高后趋于平稳,其中血清GPT活性表现为135.63、499.63 mg/kg铜组显著高于14.21、23.95、37.01 mg/kg铜组(P<0.05),血清Cu-Zn SOD活性和T-AOC表现为37.01、135.63、499.63 mg/kg铜组显著高于14.21、23.95 mg/kg铜组(P<0.05)。由此得出,摄食适宜铜水平的饲料可提升黄鳝机体的抗氧化能力,铜摄入不足或过量均会降低黄鳝的生长性能。铜主要蓄积于黄鳝肝脏及肠道,摄食高铜饲料会引发黄鳝肝脏铜蓄积量超标,并存在肝脏损伤风险,但对肌肉的食用安全性未见显著影响。以饲料系数及增重率为评价指标,60~95 g的黄鳝对饲料中铜的需求量为44.29~45.84 mg/kg。

The dietary copper requirement of rice field eel(Monopterus albus)and the accumulation rule of copper in rice field eel tissues were investigated in this experiment,which provided the basis for the dietary copper level and the food safety of rice field eel.In the present experiment,chalcanthite was used as the copper source,and 0,10.0,36.8,135.7 and 500.0 mg/kg copper were added to basal diet in the form of equal logarithmic interval,respectively.The measured values of copper level in the five diets were 14.21,23.95,37.01,135.63 and 499.63 mg/kg,respectively.The growth indexes,morphological parameters,body composition,tissue copper accumulation amount and serum biochemical indexes of rice field eel with the initial body weight of(62.09±1.07)g were measured after feeding for 60 days under the same aquaculture conditions.Each diet fed to 4 culture nets with 30 rice field eels in each culture net.The results showed as follows:with the dietary copper level increasing,the weight gain rate(WGR)and specific growth rate(SGR)of rice field eel increased firstly and then decreased,while the feed conversion rate(FCR)decreased firstly and then increased.When the dietary copper level was 37.01 mg/kg,the WGR,SGR and FCR were the best.Dietary copper level had significant effects on the copper accumulation amount in the whole fish,liver,intestine,spleen and skin(P<0.05),but had no significant difference effects on the copper accumulation amount in the muscle and kidney(P>0.05),and the muscle copper accumulation amount in each group remained at a low level.The copper accumulation amount in different tissues was in order as follows:liver>intestine>spleen>whole fish>skin,among which the 499.63 mg/kg copper group exceeded the national safety limit of copper in food(50 mg/kg).Dietary copper level had no significant effects on the serum glutamic oxaloacetic transaminase(GOT),alkaline phosphatase(AKP)and lysozyme(LZM)activities(P>0.05).With the dietary copper level increasing,the activities of alanine aminotransferase(GPT),copper-zinc superoxide dismutase(Cu-Zn SOD)and total antioxidant capacity(T-AOC)in serum of rice field eel increased firstly and then maintain stable.The serum GPT activity in 135.63 and 499.63 mg/kg copper groups was significantly higher than that in 14.21,23.95 and 37.01 mg/kg copper groups(P<0.05),and the serum Cu-Zn SOD activity and T-AOC in 37.01,135.63 and 499.63 mg/kg copper groups was significantly higher than that in 14.21 and 23.95 mg/kg copper groups(P<0.05).In conclusion,feeding appropriate copper level diet can improve the body antioxidant ability of rice field eel,and insufficient or excessive copper will reduce the growth performance of rice field eel.Copper is mainly accumulated in liver and intestine.Feeding high-copper diet will lead to copper accumulation exceed standard in liver,and there is a risk of liver injury of rice field eel,which has no obvious impact on food safety of its muscle.Using FCR and WGR as evaluation indexes,the copper requirement of 60 to 95 g rice field eel is 44.29 to 45.84 mg/kg.