饲料亮氨酸水平对幼草鱼生长、饲料利用及体成分的影响

Effect of dietary leucine level on growth, diet utilization and body composition of juvenile grass carp(Ctenopharyngodon idella)

以鱼粉和晶体氨基酸混合物为蛋白源,制作7组亮氨酸梯度水平分别为9.65、12.05、14.98、17.31、20.06、22.88、25.60 g/kg的等氮等能半精制饲料,饲喂初始体重为2.25 g的草鱼幼鱼70 d,试验结果表明:饲料亮氨酸水平对鱼体增重、饲料效率和蛋白质积累率均有显著影响(P<0.05)。草鱼鱼体增重随饲料亮氨酸水平的提高而显著增加,当饲料亮氨酸水平达14.98 g/kg干饲料时,继续增加饲料亮氨酸水平,草鱼鱼体增重则不再有显著变化。草鱼幼鱼饲料效率和蛋白质积累率表现出同鱼体增重相同的趋势。饲料亮氨酸水平对草鱼全鱼必需氨基酸、总氨基酸以及鱼体组成无显著影响(P>0.05)。饲料亮氨酸水平对草鱼肝脏谷丙转氨酶(ALT)和谷草转氨酶(AST)活力均无显著性影响(P>0.05)。分别以鱼体增重、饲料效率和蛋白质积累率为指标,以折线回归模型分析,求得草鱼幼鱼对饲料亮氨酸的需求量为15.17~15.29 g/kg干饲料,约占饲料粗蛋白的4.68%~4.71%。

A 70 d feeding trail was conducted to evaluate the optimum dietary leucine level for juvenile grass carp （Ctenopharyngodon idella）. Seven isonitrogenous diets with graded levels of leucine ranging from 9.65 g/kg to 25.60 g/kg were fed to triplicate groups of fish with an average initial body weight of 2.25 g, respectively. The results showed that weight gain, feed efficiency and protein retention efficiency increased significantly with increasing of dietary leucine level from 9.65 g/kg to 14.98 g/kg（P〈 0.05）, but appeared to keep stable with further increasing to 25.60 g/kg. And fish essential amino acids, total amino acids and whole fish composition were not affected significantly by dietary leucine level （P〉0.05）. ALT and AST activities in hepatopancreas were not affected significantly by dietary leucine level（P〉0.05）. The broken-line regression analysis with weight gain, feed efficiency and protein retention efficiency as the criteria indicated that the requirements of dietary leucine for juvenile grass carp were 15.19 g/kg, 15.29 g/kg, 15.17 g/kg of dry diet respectively. In conclusion, the dietary leucine requirement for juvenile grass carp was estimated to be 15.17-15.29 g/kg of dry diet, and 4.68%-4.71% of the dietary crude protein.