大口黑鲈对饲料中乙氧基喹啉的耐受性评价

Tolerance Evaluation of Ethoxyquin in Diets of Largemouth Bass (Micropterus salmoides)

本试验旨在通过生长性能、抗氧化应答和肝脏组织学变化研究大口黑鲈对乙氧基喹啉的耐受性。在基础饲料中依次添加0(FFO组)、150(FFO-150组)、300(FFO-300组)和1 500 mg/kg(FFO-1500组)的乙氧基喹啉,其中300和1 500 mg/kg分别是欧盟最高推荐剂量(150 mg/kg)的2和10倍。另设1个负对照组(OFO组),即以氧化鱼油替换基础饲料中的新鲜鱼油。以初始体重为(4.01±0.01)g的大口黑鲈为靶动物,进行为期10周的生长试验,每组6个重复,每个重复30尾鱼。结果表明:OFO组的生长性能最差,其余各组增重率、特定生长率、饲料系数、摄食率均差异不显著(P>0.05)。此外,FFO-300和FFO-1500组的存活率显著高于OFO和FFO组(P<0.05)。FFO-150组的肥满度显著高于OFO组(P<0.05);FFO-1500组的脏体比、肝体比与FFO组差异不显著(P>0.05),但显著高于其他各组(P<0.05)。FFO-300、FFO-1500组的肝脏谷胱甘肽硫转移酶活性显著高于其他组(P<0.05)。饲料中添加300和1 500 mg/kg乙氧基喹啉可以显著提高大口黑鲈肌肉中超氧化物歧化酶活性和总抗氧化能力(P<0.05)。乙氧基喹啉的添加对大口黑鲈鳃中抗氧化酶活性的影响无规律性变化。大口黑鲈心脏中过氧化氢酶活性、总抗氧化能力由于乙氧基喹啉的添加而显著降低(P<0.05)。肝脏、鳃、心脏中丙二醛含量随乙氧基喹啉添加量增加呈下降趋势。各组大口黑鲈的肝脏有不同程度的损伤,但FFO-150、FFO-1500组的损伤相对比较少。由此得出,饲料中添加150 mg/kg乙氧基喹啉具有一定的抗氧化保护作用且对大口黑鲈是安全的,安全系数为10倍。但从存活率和抗氧化保护功能来看,建议大口黑鲈饲料中乙氧基喹啉的最高推荐量为300 mg/kg。

A 10-week growth trial was conducted to evaluate the tolerance of largemouth bass （ Micropterus salmoides） on ethoxyquin （ EQ ） based on growth performance, antioxidant response and liver histological change. Four experimental diets were prepared with EQ supplemental levels at 0 （ FFO group） , 150 （ FFO-150 group） , 300 （ FFO-300 group） and 1 500 mg/kg （ FFO-1500 group） , in which 150 mg/kg was the maxi-mum recommended level of European Union, 300 and 1 500 mg/kg were 2 and 10 fold levels, respectively. In addition, a negative control diet （ OFO group） with oxidized fish oil to replace fresh fish oil was designed. Each diet was fed to 6 replicates with 30 largemouth bass [initial body weight=（4.01±0.01） g]. The results showed as follows： fish in OFO group showed the worst growth performance, and no significant differences were observed in weight gain rate, special gain rate, feed conversion ratio and feeding rate among other groups （P〉0.05）, while the survival rate in OFO-300 and OFO-1500 groups was significantly higher than that in OFO and FFO groups （ P〈0.05） . The condition factor in FFO-150 group was significantly increased compared with OFO group （ P〈0.05）;the hepatosomatic index and viscerasomatic index in FFO-1500 group had no sig-nificant changes compared with FFO group （ P〉0.05） , but significantly higher than those in other groups （ P〈0.05） . Glutathione S-transferase （ GST） activity in liver in FFO-300 and FFO-1500 groups was significantly higher than that in other groups （P〈0.05）. The supplementation of 300 and 1 500 mg/kg EQ could signifi-cantly enhance the superoxide dismutase （ SOD） activity and total antioxidative capability （ T-AOC） in muscle （ P〈0.05） . Antioxidant enzyme activities in gill of fish in each group changed erratically. Catalase （ CAT） ac-tivity and T-AOC in heart were significantly decreased by EQ supplementation （P〈0.05）. Malondiadehyde （ MDA） content in liver, gill and heart was decreased with EQ supplemental level increasing. Different degrees of liver histological damage were observed in every group, and fish fed diets with 150 and 1 500 mg/kg EQ re-lieved the symptom. The present study shows that the 150 mg/kg EQ has a positive effect on antioxidant and it is safe for largemouth bass. The 10 fold of safety margin is obtained by the present study. In the view of surviv-al rate and antioxidant protection, our present study suggests that the maximum recommended level of EQ is 300 mg/kg in diets of largemouth bass.