2种养殖密度模式下刀鲚幼鱼的营养成分分析

Analysis and evaluation of muscle nutrient components of Coilia nasus young fish under two cultural density levels

【目的】分析高密度和常规密度养殖模式下刀鲚幼鱼营养成分的差异,评估高密度养殖刀鲚幼鱼是否存在环境拥挤胁迫。【方法】采用池塘高密度(108240尾/hm^(2))和常规密度(62505尾/hm^(2))模式养殖刀鲚0+龄幼鱼,测定鱼体鲜样中水分、粗灰分、粗蛋白质和粗脂肪含量及干样中常见氨基酸和脂肪酸含量,采用氨基酸评分(AAS)、化学评分(CS)、必需氨基酸指数(EAAI)及支链氨基酸与芳香族氨基酸的比值(F值)等评价幼鱼肌肉的营养品质。【结果】高密度模式养殖刀鲚幼鱼的粗蛋白质和粗脂肪含量(分别为14.07%和2.50%)均较常规密度养殖模式(粗蛋白质和粗脂肪含量分别为15.16%和3.97%)显著降低(P<0.05),而水分和粗灰分含量差异均不显著(P>0.05)。高密度养殖模式的精氨酸和色氨酸含量显著高于常规密度模式(P<0.05),而组氨酸含量显著低于常规密度模式(P<0.05),其余15种氨基酸的含量在两模式间差异均不显著(P>0.05);刀鲚幼鱼干样中常见氨基酸总量(TAA)、必需氨基酸(EAA)、半必需氨基酸(HEAA)、非必需氨基酸(NEAA)、鲜味氨基酸(DAA)、EAA/TAA、EAA/NEAA和DAA/TAA在两模式之间的差异均不显著(P>0.05);2种养殖密度模式下刀鲚幼鱼的必需氨基酸指数(EAAI)和F值均非常接近。在检测到的28种脂肪酸中,有22种脂肪酸的相对含量在两模式之间存在显著差异(P<0.05);主要脂肪酸中,高密度养殖模式的C18:1n9c、C16:1、C18:3n3、C20:2和C20:5n3(EPA)相对含量均显著低于常规密度模式(P<0.05),而C18:0、C22:2、C20:4n6、C22:5n3(DPA)和C22:6n3(DHA)的相对含量均显著高于常规密度模式(P<0.05)。高密度养殖模式的饱和脂肪酸(SFA)、多不饱和脂肪酸(PUFA)和n3多不饱和脂肪酸/n6多不饱和脂肪酸显著高于常规密度模式(P<0.05),而单不饱和脂肪酸(MUFA)显著低于常规密度模式(P<0.05)。【结论】池塘高密度养殖不会造成刀鲚幼鱼鱼体蛋白质品质的下降,但高密度养殖模式下刀鲚幼鱼鱼体的粗蛋白、粗脂肪含量和MUFA显著下降,PUFA和n3PUFA/n6PUFA显著升高,说明高密度养殖模式下刀鲚幼鱼已经受到环境拥挤胁迫,因此刀鲚幼鱼的池塘养殖密度以不超过108240尾/hm^(2)为宜。

【Objective】This study analyzed the differences of nutritional components of Coilia nasus under high and conventional cultural density levels and evaluated whether young C.nasus fish cultured under high density was oppressed by the crowded environment.【Method】C.nasus young fish(0+age)were cultured at high density(108240 ind/hm^(2))and conventional density(62505 ind/hm^(2))in pond.Contents of moisture,crude ash,crude protein and crude fat in fresh fish samples and contents of common amino acids and fatty acids in dry fish samples were determined.Then,the nutritional quality was evaluated by amino acid score(AAS),chemical score(CS),essential amino acid index(EAAI)and the ratio of branched chain amino acids to aromatic amino acids(F value).【Result】The crude protein content(14.07%)and crude fat content(2.50%)of high density were significantly lower than that of conventional density(15.16%and 3.97%)(P<0.05).No significant difference was found in moisture and crude ash contents between the two levels(P>0.05).The arginine and tryptophan contents of high density were significantly higher than that of conventional density(P<0.05),while the histidine content of high density was significantly lower than that of conventional density(P<0.05).There was no significant difference(P>0.05)in contents of other 15 amino acids.There was no significant difference in total common amino acid(TAA),total essential amino acid(EAA),total half-essential amino acid(HEAA),total non-essential amino acid(NEAA)and total delicious amino acid(DAA)contents as well as EAA/TAA,EAA/NEAA and DAA/TAA specific values in dry samples between the two levels(P>0.05).The EAAI and F value of the two levels were very close.Among the detected 28 fatty acids,there were significant differences in contents of 22 kinds of fatty acids(P<0.05).Amongst major fatty acids,contents of C18:1n9c,C16:1,C18:3n3,C20:2 and C20:5n3 of high density were significantly lower than that of conventional density(P<0.05),while contents of C18:0,C22:2,C20:4n6,C22:5n3 and C22:6n3 of high density were significantly higher than that of conventional density(P<0.05).The total saturated lipid acid(SFA)(34.49%),total polyunsaturated fatty acids(PUFA)(30.22%)and n3PUFA/n6PUFA(2.66)of high density were significantly higher than that of conventional density(32.65%,28.71%and 2.55)(P<0.05),while the content of total monounsaturated fatty acids(MUFA)(35.29%)of high density was significantly lower than that of conventional density(38.64%)(P<0.05).【Conclusion】Although high density culture in pond did not decrease protein quality of C.nasus young fish,it significantly decreased crude protein,crude fat and MUFA and significantly increased PUFA and n3PUFA/n6PUFA.It is indicated that C.nasus young fish cultured under high density level was stressed by overcrowding.The suggested stocking density of C.nasus young fish in pond is no more than 108240 ind/hm^(2).