Habte-Tsion Habte-Michael, Ren Mingchun, Liu Bo, Xie Jun, Ge Xianping, Chen Ruli, Zhou Qunlan, Pan Liangkun
Wuxi Fisheries College, Nanjing Agricultural University,Shanshui East Road No. 9,Wuxi,Jiangsu214081,People's Republic of China.
Key Laboratory for Genetic Breeding of Aquatic Animals and Aquaculture Biology, Freshwater Fisheries Research Center, Chinese Academy of Fishery Sciences,Shanshui East Road No. 9,Wuxi,Jiangsu214081,People's Republic of China.
Br J Nutr. 2015 Aug 28;114(4):533-43. doi: 10.1017/S0007114515002196. Epub 2015 Jul 23.
The present study conducted a 9-week feeding trial to investigate the effects of threonine (Thr) on the digestion capacity and hepatopancreas gene expression of juvenile blunt snout bream (Megalobrama amblycephala). For this purpose, three tanks (300 litres/tank) were randomly arranged and assigned to each experimental diet. Juvenile fish were fed with diets containing graded Thr levels (0·58, 1·08, 1·58, 2·08 or 2·58 % of the diet) to apparent satiation four times daily. At the end of the feeding trial, the results indicated that hepatopancreas weight, hepatosomatic index, hepatopancreatic protein content, intestinal weight, intestosomatic index and intestinal protein content increased with increasing dietary Thr levels up to 1·58 % and thereafter decreased (P< 0·05). The activities of chymotrypsin, trypsin, amylase and lipase elevated as dietary Thr levels increased up to 1·58 % (P< 0·05), while these activities decreased in most cases after 1·58 % dietary Thr except for chymotrypsin and trypsin in the hepatopancreas (plateau 1·58-2·08 % Thr). The relative gene expression levels of chymotrypsin, trypsin, amylase, lipase, target of rapamycin and insulin-like growth factor-I were up-regulated, and the highest values were observed with 1·58 % dietary Thr or 1·58 and 2·08 % dietary Thr, whereas the relative gene expression levels of eukaryotic translation initiation factor 4E-binding protein 2 gradually decreased (P< 0·10) as dietary Thr levels increased up to 1·58 % and thereafter significantly increased (P< 0·05), which could explain that about 1·58 % dietary Thr could improve the growth and development of digestive organs and activities of digestive enzymes of juvenile blunt snout bream.
本研究进行了为期9周的饲养试验，以研究苏氨酸（Thr）对团头鲂幼鱼消化能力和肝胰腺基因表达的影响。为此，随机安排了三个水箱（每个水箱300升），并分别投喂每种实验饲料。幼鱼每天投喂含不同梯度Thr水平（占饲料的0·58%、1·08%、1·58%、2·08%或2·58%）的饲料，直至明显饱足，每天投喂4次。饲养试验结束时，结果表明，肝胰腺重量、肝体指数、肝胰腺蛋白质含量、肠道重量、肠体指数和肠道蛋白质含量随着饲料中Thr水平的增加而增加，直至1·58%，此后下降（P<0·05）。随着饲料中Thr水平增加至1·58%，胰凝乳蛋白酶、胰蛋白酶、淀粉酶和脂肪酶的活性升高（P<0·05），而在饲料中Thr水平超过1·58%后，大多数情况下这些酶的活性下降，但肝胰腺中的胰凝乳蛋白酶和胰蛋白酶除外（在1·58%至2·08%的Thr水平时达到平稳）。胰凝乳蛋白酶、胰蛋白酶、淀粉酶、脂肪酶、雷帕霉素靶蛋白和胰岛素样生长因子-I的相对基因表达水平上调，在饲料中Thr水平为1·58%或1·58%和2·08%时观察到最高值，而真核翻译起始因子4E结合蛋白2的相对基因表达水平随着饲料中Thr水平增加至1·58%而逐渐下降（P<0·10），此后显著增加（P<0·05），这可以解释饲料中约1·58%的Thr可以促进团头鲂幼鱼消化器官的生长发育和消化酶的活性。
