鱤幼鱼对晶体氨基酸的利用效果及赖氨酸需求量的研究

本试验旨在探讨鱤幼鱼对晶体氨基酸的利用效果,并在此基础上确定鱤幼鱼赖氨酸的需求量.试验设计7组等氮饲料,其中对照组饲料蛋白质源全部为结合蛋白(鱼粉和酪蛋白),试验组饲料在对照组饲料的基础上利用晶体氨基酸替代部分酪蛋白,并通过添加不同水平的L-赖氨酸盐酸盐使赖氨酸水平在1.9％～4.5％之间(0.5％的梯度).试验选取初始体重为(2.36±0.08)g的鱤幼鱼378尾,随机分为7组(每组3个重复,每个重复18尾鱼),每组随机饲喂1种试验饲料.试验期为8周.结果表明:使用晶体氨基酸替代部分酪蛋白后,鱤幼鱼的生长性能虽有不同程度的下降,但3.46％和3.94％组的特定生长率与对照组无显著差异(P＜0.05),2.45％、2.95％、3.46％和3.94％组的饲料系数与对照组无显著差异(P＞0.05).各试验组的干物质、蛋白质和脂肪表观消化率均显著高于对照组(P＜0.05).鱤幼鱼的增重率,特定生长率,干物质和蛋白质表观消化率,肝胰脏脂肪酶活性,血清总蛋白、总胆固醇含量以及血清碱性磷酸酶活性均随饲料赖氨酸水平的升高而呈现先升高后降低的趋势.综上所述,鱤幼鱼可以利用饲料中的晶体氨基酸,利用效果与饲料氨基酸组成的平衡性有关；以增重率为指标,通过二次曲线模型得出鱤幼鱼赖氨酸需求量为饲料干重的3.40％(饲料粗蛋白质含量为饲料干重的46％).

Utilization Effects of Crystalline Amino Acids and Requirement of Lysine for Juvenile Yellowcheek Carp(Elopichthys bambusa)

An 8-week feeding trial was conducted to evaluate the utilization effects of crystalline amino acids for juvenile yellowcheek carp(Elopichthys bambusa),and to determine the dietary lysine requirement.Seven isonitrogenous diets were formulated.The diet which had conjugated proteins(fish meal and casein) as the only protein source was control group diet.In the diets of experimental groups,crystalline amino acids were used to replace part of casein on the basis of the control group diet,and different levels of L-lysine·HCl were supplemented into the above diets to achieve lysine levels from 1.9% to 4.5% with a 0.5% increment.A total of 378 juvenile yellowcheek carp with initial body weight of(2.36±0.08) g were randomly divided into 7 groups with 3 replicates per group and 18 fish per replicate,and each group were randomly fed one of the 7 experimental diets.The results showed as follows: although growth performance appeared different degrees of decline when part of casein replaced by crystalline amino acids,the special gain rate of 3.46% and 3.94% groups had no significant difference compared with the control group(P<0.05),and feed conversation ratio of 2.45%,2.95%,3.46% and 3.94% groups had no significant difference compared with the control group(P<0.05).The apparent digestibility of dry matter,protein and lipid of experimental groups were significantly higher than those of control group(P>0.05).The weight gain rate,special gain rate,apparent digestibility of dry matter and protein,hepatopancreas lipase activity,serum protein and cholesterol contents,and serum alkaline phosphatase activity of juvenile yellowcheek carp had a trend first increased and then decreased with increasing dietary lysine level.It is concluded that crystalline amino acids can be used by juvenile yellowcheek carp,and the utilization effects are related to the balance of amino acid composition.Using weight gain rate as index,quadratic curve model indicate that the optimal dietary lysine requirement for juvenile yellowcheek carp is 3.40%(DM basis) when dietary crude protein content is 46%(DM basis).