鲈鱼(Lateolabrax japonicus)生长后期对苏氨酸需要量

Threonine Requirement of Japanese Seabass (Lateolabrax japonicus) in Mature Stages

中文关键词: 鲈鱼  苏氨酸  生长  需求量  生长后期

英文关键词: Lateolabrax japonicus  Threonine  Growth performance  Requirement  Mature stages

中文摘要:

      在半精制饲料中分别添加0、0.35%、0.70%、1.05%、1.40%、1.75%苏氨酸，制成苏氨酸实际梯度为1.05%、1.35%、1.65%、2.00%、2.42%、2.65%的6组等能等氮饲料(44.67%粗蛋白质，21.65 kJ/g总能)，对初始体重为(333.93±6.60) g的鲈鱼(Lateolabrax japonicus)在海水浮式网箱(1.5 m× 1.5 m×2.0 m)中进行了70 d的喂养实验，研究其对苏氨酸的最适需求量。结果显示，鲈鱼成活率在89.58%–95.83%之间，各处理组之间无显著差异(P>0.05)；随着饲料中苏氨酸水平的升高，鲈鱼的特定生长率(SGR)显著增加(P<0.05)，且在2.00%苏氨酸饲料组出现最大值，但随着苏氨酸水平的继续升高，SGR呈减小的趋势；饲料效率(FE)随饲料中苏氨酸水平的升高呈先增加后减小的趋势，2.00%苏氨酸组的FE显著高于1.05%组及2.65%组(P<0.05)；随着饲料中苏氨酸水平的升高，蛋白质沉积率(PPV)呈先增加后减小的趋势，且于2.00%苏氨酸组出现最大值；肝脏谷草转氨酶、谷丙转氨酶活性随饲料中苏氨酸水平的升高呈先增加后减小的趋势；饲料中不同水平苏氨酸对鱼体粗蛋白、粗脂肪、粗灰分无显著影响(P>0.05)。以特定生长率、饲料效率及蛋白质沉积率为评价指标，经二次回归分析得出，鲈鱼对饲料中苏氨酸的最适需求量分别为占饲料干重的1.84%、1.87%及1.83%，占饲料蛋白质的4.11%、4.18%及4.09%。

英文摘要:

      It has been clear that the dietary threonine is essential in the growth of juvenile Japanese seabass, and the requirement of threonine could vary at different growth stages. It is necessary to identify the requirement of threonine at mature stages. We designed a 10-week feeding experiment to investigate the effects of threonine on the growth performance of Japanese seabass and to determine the optimal level of dietary threonine. Six isonitrogenous and isoenergetic semipurified diets (44.67% crude protein, 21.65 kJ/g gross energy) were formulated with graded levels of crystalline threonine (0, 0.35%, 0.70%, 1.05%, 1.40%, and 1.75%). The actual levels of threonine were determined to be 1.05%, 1.35%, 1.65%, 2.00%, 2.42%, and 2.65% in the dry diets, respectively, and then used them to feed the six groups of Japanese seabass (average body weight: 333.93±6.60 g). The result showed that no significant differences in survival rate (89.58%95.83%) were found among dietary treatments (P>0.05). With the increasing of dietary threonine levels, the specific growth rate (SGR), feed efficiency (FE) and protein productive value (PPV) increased significantly (P<0.05), then these indexes showed a declining tendency after reaching their peaks at the 2.00% dietary threonine level. The activities of glutamic-oxaloacetic transaminase (GOT) in livers observably increased when threonine level was increased from 1.05% to 2.00% (P<0.05), and then decreased when the threonine level was increased from 2.00% to 2.65%. The highest activity of glutamic-pyruvic transaminase (GPT) in liver was obtained in fish fed with 2.00% of dietary threonine. However there was no significant difference in the body composition between different dietary treatments (P>0.05). The second-order regression analysis based on different parameters (SGR, FE, and PPV) indicated that the optimal levels of dietary threonine were 1.84%, 1.87% and 1.87% (of diet), and 4.11%, 4.18% and 4.09% (of dietary protein) respectively.