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饲料中DHA/EPA值对星斑川鲽幼鱼生长、体组成及血清生理指标的影响

Effect of dietary DHA to EPA ratios on growth performance, body composition and serum physiological parameters in juvenile Platichthys stellatus

    摘要
  • 摘要: 为研究饲料DHA/EPA值对星斑川鲽幼鱼生长、体组成和血液生理指标的影响，实验配制等氮、等能的5种不同DHA/EPA值（0.64、0.97、1.18、1.59和1.91）的饲料，每个比值设3个重复，饲养周期56 d。结果显示：（1）随着饲料DHA/EPA值的升高，星斑川鲽幼鱼增重率、饲料效率、蛋白质效率均呈先上升后下降的趋势（P<0.05）。当饲料DHA/EPA值为0.97～1.59时实验鱼增重最快，饲料效率最高。蛋白质效率则在DHA/EPA值为0.97～1.18时达到最高。蛋白质沉积率（protein retention efficiency，PRE）与饲料DHA/EPA值呈显著二次回归关系（y=-1.589 5x2+2.858 3x+45.184；R2=0.910 8，x=饲料DHA/EPA值，y=PRE），当饲料DHA/EPA值大于0.90时呈下降趋势。肝体比呈先下降后小幅回升的趋势（P<0.05），在饲料DHA/EPA值为1.18时达到最低，为2.85%，脾脏指数呈显著上升趋势（P<0.05），于饲料DHA/EPA值为1.59组最高（0.12%）；（2）肝脏粗脂肪含量随饲料DHA/EPA值的增加呈明显下降趋势（P<0.05），且在饲料DHA/EPA值为1.18时降到最低，为8.60%，而后又显著上升，但仍显著低于饲料DHA/EPA值为0.64时的水平（13.44%）。二次回归分析（y=5.199 6x2-15.652x+20.866；R2=0.634 8，x=饲料DHA/EPA值，y=肝脏脂肪含量）显示，当饲料中DHA/EPA值为1.51时肝脏脂肪含量最低。脂肪酸分析结果显示，随着饲料DHA/EPA值的升高，肝脏及肌肉中EPA含量均呈线性下降趋势（P<0.05），而DHA含量及DHA/EPA均呈直线上升趋势（P<0.05）。肝脏和肌肉组织n-3 HUFA总量不受饲料处理的影响（P>0.05）；（3）血清总蛋白、球蛋白含量在饲料DHA/EPA值为1.59时显著高于其他各组（P<0.05），白蛋白在饲料DHA/EPA值为0.64、0.97和1.59水平最高。溶菌酶（LSZ）活性在饲料DHA/EPA值为1.18时达到峰值（P<0.05），为2.76 μg/mL。谷丙转氨酶（ALT）活性在饲料DHA/EPA值<1.91时无显著变化，而当饲料DHA/EPA>1.18时，血清谷草转氨酶（AST）活性提高了65%左右。研究表明，在本实验条件下，以增重率为参考指标，采用二次回归（y=-31.066x2+77.26x+76.541；R2=0.957 4，x=饲料DHA/EPA值，y=增重率）分析可得，当饲料脂肪水平为8.3%，n-3 HUFA含量为0.74%时，星斑川鲽幼鱼初始体质量（31.70±0.12）g对DHA/EPA值的最适需要量应为1.24。

     

    Abstract: An 8-week feeding trial was conducted in a recirculated system to study the effect of dietary DHA to EPA ratios(0.64,0.97,1.18,1.59 and 1.91),with 0.74% n-3 HUFA and 8.3% lipid in dry feed,on growth performance,body composition and blood biological parameters in juvenile starry flounder,Platichthys stellatus.The results showed that:(1)fish weight gain rate(WGR),feed efficiency(FE),as well as protein efficiency ratio(PER)increased and then decreased with higher DHA/EPA values(P<0.05).Quadratic regression(y=-1.589 5x2+2.858 3x+45.184;R2 =0.910 8,x=dietary DHA/EPA ratios,y=PRE)showed PRE decreases significantly beyond the DHA/EPA ratio of 0.90.Spleensomatic index(SSI)was enhanced by dietary DHA/EPA ratios and showed highest values of 0.12% in DHA/EPA ratio of 1.59,whereas hepatosomatic index(HSI)was decreased and then increased by dietary DHA/EPA ratios(P<0.05),with the lowest value being in DHA/EPA ratio of 1.18(2.85%).(2)Liver lipid was obviously decreased(from 13.44% to 8.60%)by dietary DHA/EPA ratios lower than 1.18,and then increased slightly.Quadratic analysis(y=5.199 6x2-15.652x+20.866;R2=0.634 8,x=dietary DHA/EPA ratios,y=liver lipid content)suggests the optimum DHA/EPA ratio is 1.51 based on liver lipid deposition.Liver and muscle EPA contents were reduced linearly,however,DHA contents as well as DHA/EPA ratios were elevated linearly by dietary DHA/EPA ratios.Exclusively,total content of n-3 HUFA in both tissues were unaffected by dietary treatments.(3)Among all serum physiological parameters,both total protein and globulin showed their highest values at the DHA/EPA ratio of 1.59,while fish fed diets with DHA/EPA ratios of 0.64,0.97 and 1.59 presented higher albumin content.Lysozyme(LSZ)reached the top in fish fed diet with dietary DHA/EPA ratio of 1.18.Alanine aminotransferase(ALT)remained unchanged when the dietary DHA/EPA ratios were lower than 1.91,while dietary DHA/EPA ratios higher than 1.18 increased the aspertate aminotransferase(AST)activities by about 65%(P<0.05).In conclusion,under the present experimental conditions,based on fish weight gain rate(WGR),quadratic regression analysis(y=-31.066x2+77.26x+76.541;R2=0.957 4,x=dietary DHA/EPA ratios,y=weight gain rate)shows that the optimum DHA/EPA ratio for juvenile starry flounderinitial body weight,(31.70±0.12)gis 1.24.

     

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