N-氨甲酰谷氨酸对罗非鱼幼鱼生长、血液氨基酸组成及脂肪沉积的影响

摘要

为研究精氨酸对尼罗罗非鱼(Oreochromis niloticus)的生物学效应,采用精氨酸内源合成途径的必需辅助因子N-氨甲酰谷氨酸(NCG)代替精氨酸, 研究不同剂量包被NCG制剂(实际NCG含量为80%)对尼罗罗非鱼生长及脂肪沉积的影响.实验共设 6 个制剂添加组, 分别为 0.025%、0.05%、0.1%、0.2%、0.4%、0.5%及对照组.结果显示, 罗非鱼血液中所有 NCG 添加组(0.025%—0.5%)和对照组相比, 赖氨酸、苏氨酸、亮氨酸、异亮氨酸、缬氨酸等必需氨基酸含量无显著性差异(P>0.05), 而当 NCG 添加量为 0.4%时, 精氨酸含量显著高于其他各组(P<0.05), 且约为对照组的4倍, 继续提高NCG添加量至0.5%时, 精氨酸含量无显著提高(P>0.05); 所有 NCG 添加组的末均重、特定生长率、饲料系数、内脏比和肥满度等指标与对照组相比均无显著性差异(P>0.05), 当 NCG 添加量为 0.2%时, 增重率和蛋白质效率均显著高于其他组(P<0.05), 除了0.1%NCG添加组, 其他各组全鱼蛋白质含量均高于对照组; 脂肪沉积方面, 所有NCG添加组均显示肝体比显著低于对照组(P<0.05),全鱼干物质中脂肪含量显著高于对照组 (P<0.05),脂肪有从肝转移至肌肉的倾向.饲料中添加0.4%NCG, 对于血液中精氨酸含量的提高有较好的促进作用, 而且不影响其他氨基酸的吸收;饲料中添加0.025%—0.5% NCG有利于减少肝脏脂肪沉积而增加了肌肉中的脂肪沉积,研究结果为进一步开展精氨酸影响鱼体脂肪沉积的机理研究提供了科学依据.%The direct addition of arginine into diets causes malabsorption of other amino acids in farmed fish. To study the biological effects of arginine in Nile tilapia, we replaced arginine with N-Carbamylglutamate (NCG), an essential cofactor glutamate in the endogenous arginine synthesis pathway. We examined the effects of NCG (actual content of 80%) in different doses (0.025%, 0.05%, 0.1 %, 0.2 %, 0.4 % and 0.5%) on the concentration of amino acids in the blood, the growth, and the fat deposition in Nile tilapia. The results showed that there was no significant difference be-tween the control group and the NCG-containing groups in the levels of lysine, threonine, leucine, valine and isoleucine in the blood. The blood arginine level increased significantly in the fish fed with 0.4% NCG, which was four times as the control group, but there was no difference in the fish fed with 0.5% NGG compared to the control (P>0.05). In terms of the final weight gain rate, the specific growth rate, the feed coefficient rate, the viscera-somatic index and the condition factor, there were no differences between the NCG groups and the control group (P>0.05). The weight gain and the protein efficiency ratio were significantly elevated in the fish fed with 0.2% NCG (P<0.05). The whole fish protein content of all NCG groups, except for the group of 0.1% NCG addition, was significantly higher than that of the control group (P<0.05). The hepatosomatic index of all NCG groups was significantly lower than that of the control group (P<0.05), and the whole fish fat content of the NCG groups was higher than that of the control group, except for the group of 0.1% NCG addition, which implied the transfer of fats from the liver to the muscles. The diet containing 0.4% NCG effectively improved the arginine level in the blood but did not affect the absorption of other amino acids. The diet with 0.025%—0.5% NCG reduced the liver fat deposition and increased the muscle fat deposition. Our results should provide important information for future studies on the effects of arginine on fish fat deposition.