Wu Chenglong, Chen Lian, Lu Zhibin, Gao Jun'e, Chu Yudan, Li Liang, Wang Ming, Zhang Geying, Zhang Miaotong, Ye Jinyun
College of Life Science, Huzhou University, 759 East 2nd Road, Huzhou 313000, PR China.
College of Life Science, Huzhou University, 759 East 2nd Road, Huzhou 313000, PR China.
Fish Shellfish Immunol. 2017 Aug;67:419-428. doi: 10.1016/j.fsi.2017.06.033. Epub 2017 Jun 13.
The present study was focused on the growth, body composition, metabolic abilities and innate immune responses in juvenile black carp Mylopharyngodon piceus fed with six levels of dietary leucine (7.3, 12.4, 16.2, 21.9, 28.3 and 34.5 g kg) for 9 weeks. Results showed that the highest weight gain (WG) and the lowest feed conversion ratio (FCR) was obtained at 23.5 and 23.9 g kg dietary leucine using second-order polynomial model, respectively. Adequate dietary leucine content (21.9 and 28.3 g kg) could significantly up-regulate the expression levels of neuropeptide Y (NPY) and ghrelin (GRL) in the brain of black carp juveniles. The protein efficiency ratio (PER), feed efficiency ratio (FER) and protein deposition ratio (PDR) were also significantly increased by adequate dietary leucine content (21.9 and 28.3 g kg) (p < 0.05). Adequate dietary leucine content (21.9 and 28.3 g kg) could significantly up-regulate the activities of metabolic enzymes, such as α amylase, trypsin, chymotrypsin and elastase in the liver of Black carp (p < 0.05). However, the activities of alanine transaminase (ALT), aspartate aminotransferase (AST) and leucine aminopeptidase (LAP) were significantly reduced in the fish serum by adequate dietary leucine content (21.9 and 28.3 g kg) compared with leucine-deficient diet (7.3 and 12.4 g kg). In addition, 21.9 and 28.3 g kg dietary leucine could significantly increase complement component 3 (C3) and C4 contents, lysozyme (LYZ) activities in the serum compared with the leucine-deficient diet (7.3 and 12.4 g kg) (p < 0.05). Furthermore, optimal dietary leucine could also significantly up-regulate the mRNA expression levels of LYZ, interferon α (IFN-α), hepcidin (HEPC), natural resistance-associated macrophage protein (NRAMP), C3 and C9 in the blood of juvenile black carp compared with the leucine-deficient diets (7.3 and 12.4 g kg) (p < 0.05). In conclusion, these results suggest that adequate dietary leucine (21.9 and 28.3 g kg) could increase growth performances, improve metabolic abilities and then enhance non-specific immunities in black carp juveniles.
本研究聚焦于投喂六种不同亮氨酸水平（7.3、12.4、16.2、21.9、28.3和34.5 g/kg）饲料9周的青鱼幼鱼的生长、体成分、代谢能力和先天免疫反应。结果表明，使用二阶多项式模型分别在饲料亮氨酸含量为23.5和23.9 g/kg时获得了最高增重（WG）和最低饲料转化率（FCR）。饲料中充足的亮氨酸含量（21.9和28.3 g/kg）可显著上调青鱼幼鱼脑中神经肽Y（NPY）和胃饥饿素（GRL）的表达水平。饲料中充足的亮氨酸含量（21.9和28.3 g/kg）也显著提高了蛋白质效率比（PER）、饲料效率比（FER）和蛋白质沉积率（PDR）（p < 0.05）。饲料中充足的亮氨酸含量（21.9和28.3 g/kg）可显著上调青鱼肝脏中代谢酶如α淀粉酶、胰蛋白酶、糜蛋白酶和弹性蛋白酶的活性（p < 0.05）。然而，与亮氨酸缺乏的饲料（7.3和12.4 g/kg）相比，饲料中充足的亮氨酸含量（21.9和28.3 g/kg）可显著降低鱼血清中丙氨酸转氨酶（ALT）、天冬氨酸转氨酶（AST）和亮氨酸氨肽酶（LAP）的活性。此外，与亮氨酸缺乏的饲料（7.3和12.4 g/kg）相比，饲料中21.9和28.3 g/kg的亮氨酸可显著提高血清中补体成分3（C3）和C4含量、溶菌酶（LYZ）活性（p < 0.05）。此外，与亮氨酸缺乏的饲料（7.3和12.4 g/kg）相比，最佳饲料亮氨酸还可显著上调青鱼幼鱼血液中LYZ、干扰素α（IFN-α）抗菌肽（HEPC）、天然抗性相关巨噬蛋白（NRAMP）、C3和C9的mRNA表达水平（p < 0.05）。总之，这些结果表明，饲料中充足的亮氨酸（21.9和28.3 g/kg）可提高青鱼幼鱼的生长性能，改善代谢能力，进而增强其非特异性免疫力。
