基于稳定同位素分析不同蛋白源对大菱鲆生长的影响

THE NUTRIONAL CONTRIBUTIONS OF DIETARY PROTEIN SOURCES TO GROWTH OF TURBOT(SCOPHTHATMUS MAXIMUS L.): EVIDENCE FROM STABLE ISOTOPE ANALYSIS(SIA)

实验采用混合植物蛋白(玉米蛋白和大豆浓缩蛋白等氮1∶1混合)替代鱼粉蛋白投喂大菱鲆,通过测定不同饲料组和体组织中氮稳定同位素的值,估算氮同位素的周转率及不同蛋白源对大菱鲆生长的贡献比例。实验设计了4种配合饲料,在等氮等能的基础上,以混合植物蛋白分别替代饲料中0、10%、30%和50%的鱼粉蛋白,即CS0、CS10、CS30和CS50。将初始体重为(57.72±0.25)g的大菱鲆分成4组,每组设3个平行,实验周期为56d。实验开始后的7d、14d、28d、42d和56d采集并测定大菱鲆肌肉和肝脏中氮稳定同位素值(δ15N)。研究结果表明,当替代量达到50%时,大菱鲆摄食率和特定生长率显著低于其他组(P<0.05),而饲料系数显著高于其他组(P<0.05)。不同实验组间氮同位素的周转率均存在显著性差异(P<0.05),对照组的周转速度最快。各实验组肝脏的周转率均显著快于肌肉(P<0.05)。大菱鲆肌肉中氮同位素的周转半衰期(23.96—32.42d)显著高于肝脏的(12.38—16.83d)(P<0.05)。生长作用对大菱鲆肌肉氮同位素周转的贡献比例为57.33%—73.33%,而对肝脏的贡献比例为29.17%—36.10%。基于时间的周转模型估算氮同位素分馏系数(Δ)为1.83‰—2.83‰。采用Isosource软件计算显示,CS10、CS30和CS50组中鱼粉、玉米蛋白和SPC三种蛋白源对大菱鲆生长的贡献比例分别为80%、7%和13%,62%、11%和27%,46%、13%和41%。研究结果表明:生长作用和代谢作用共同驱动了氮稳定同位素在大菱鲆体组织中的周转代谢;氮稳定同位素在肝脏组织中的周转速度明显快于肌肉的,相应的周转半衰期更短;各实验组中SPC对大菱鲆生长的贡献均优于玉米蛋白。

To investigate effects of dietary protein sources to turbot growth (Scophthatmus maximus L.), we substitutedfish meal by plant protein blend (corn gluten and soy protein concentrate 1∶1 isonitrogenous mixed) in diets and determinednitrogen stable isotope ratios of diet and tissue. Four isonitrogenous and isoenergetic diets with different replacement0, 10%, 30% and 50% fish meal protein by plant protein blend were formulated and correspondingly named asCS0, CS10, CS30 and CS50, respectively, for a 56 days experiment with 3 replicates in each group. Our results showedthat food intake (FI) and specific growth rate (SGR) in CS50 were significantly lower but the feed coefficiency washigher compared with other groups. The turnover rates of nitrogen stable isotope were significantly different betweeneach diet (P<0.05) with the highest turnover rate in the control group. Liver responded more quickly to the diet comparedwith muscle. Nitrogen half-lives (T0.5) of muscle were significantly higher than those of liver (P<0.05). The proportionalcontributions of growth to nitrogen turnover were 57.33%—73.33% for muscle and 29.17%—36.10% for liver,respectively. Based on turnover model, the fractionation (Δ) were ranged from 1.83‰ to 2.83‰. Calculated by Isosourcesoftware, the contributions of fish meal, corn gluten and SPC to tissue growth and metabolism of turbot were80%, 7% and 13% for CS10, 62%, 11% and 27% for CS30, 46%, 13% and 41% for CS50, respectively. The resultshowed that stable isotopic turnover was driven by both tissue replacement in the form of metabolism and tissue increasein the form of growth, the proportional contritetiens of which between tissues exhibited significant discrepancy; nitrogen stable isotope, turnover rate of liver was faster than that of muscle, without, the half-time of liver was alsofaster; the contribution rate of dietary corn protein to the protein growth of the turbot was lower than the SPC.