不同小麦淀粉和脂肪水平对大黄鱼的生长性能、饲料利用及糖代谢关键酶活力的影响

为探讨饲料中添加不同小麦淀粉和脂肪水平对大黄鱼幼鱼生长、饲料利用以及糖代谢关键酶活力的影响,进行了为期8周的生长实验。设计了3个小麦淀粉水平(5%、10%和30%)和2个脂肪水平(5%和10%)的3×2的两因子实验,配制了6种等氮的饲料,分别喂养平均体质量为(6.75±0.12)g的大黄鱼幼鱼。结果显示,饲料中小麦淀粉和脂肪水平对大黄鱼增重率(WG)、特定生长率(SGR)、饲料效率(FE)、成活率(SR)、肝体比(HSI)和肥满度(CF)无显著交互作用,对脏体比(VSI)有显著交互作用。在同一脂肪水平下,淀粉水平为30%组WG和SGR显著高于10%淀粉组。不同小麦淀粉和脂肪水平对肝糖原含量无显著交互作用,而对肌糖原含量有显著交互作用,在饲料脂肪水平为5%时,30%小麦淀粉水平下的肝糖原含量显著高于10%和20%淀粉水平,10%淀粉水平下的肌糖原含量显著高于20%和30%淀粉水平;在脂肪水平为10%时,10%淀粉水平下的肝糖原含量显著高于20%和30%淀粉水平,而30%小麦淀粉水平下的肌糖原含量显著高于10%和20%淀粉水平。小麦淀粉和脂肪水平对血清中谷丙转氨酶(ALT)、谷草转氨酶(AST)、总胆固醇(TC)和葡萄糖(GLU)含量无显著交互作用,对总蛋白(TP)和甘油三酯(TG)交互作用显著。不同小麦淀粉和脂肪水平对肝脏脂肪酶活性有显著的交互作用,对淀粉酶活性无显著交互作用;同一脂肪水平下,脂肪酶的活性随着淀粉水平的升高而升高,同一饲料淀粉水平下,饲料脂肪水平为10%组的脂肪酶活性显著高于5%组。不同小麦淀粉和脂肪水平对肝脏丙酮酸激酶(PK)的活性有显著的交互作用,而对葡萄糖激酶(GK)、磷酸果糖激酶(PFK)、磷酸烯醇式丙酮酸羧激酶(PEPCK)、1,6-二磷酸果糖酶(FBPase)和6-磷酸葡萄糖酶(G6Pase)的活性均无显著交互作用。研究表明,当饲料脂肪水平为5%时,大黄鱼能够通过调节糖酵解关键酶活性及肝糖原含量来维持血糖平衡,改善对小麦淀粉的利用能力;而当脂肪水平为10%时,大黄鱼对小麦淀粉的利用能力降低。

Effects of different wheat starch and lipid levels on growth performance, feed utilization and hepatic carbohydrate metabolism key enzymes activities in large yellow croaker (Larimichthys crocea)

An 8-week feeding trial was conducted to evaluate the effects of different dietary wheat starch and lipid levels on growth performance, feed utilization and hepatic glycolysis and gluconeogenic key enzyme activities of large yellow croaker. Six isonitrogenous diets were formulated to contain three wheat starch levels (5%, 10% and 30%) and two lipid levels (5% and 10%), respectively. Each diet was randomly assigned to feed three replicate groups of juvenile large yellow croakers with the initial weight of 6.75±0.12 g and fed twice daily to apparent satiation. The results indicated that dietary wheat starch and lipid levels didn''t have significant influence on weight gain (WG), specific growth rate (SGR), feed efficiency (FE), survival rate (SR), hepatosomatic index (HSI) and condition factor (CF), however, viscerosomatic index (VSI) were significantly influenced by the dietary wheat starch and lipid levels. When the dietary lipid level was the same, fish fed the diet containing 30% wheat starch level had higher WG and SGR than those fed the diet containing 10% wheat starch. Glycogen content in muscle was significantly affected by dietary wheat starch and lipid levels, but hepatic glycogen content wasn''t significantly influenced by dietary different wheat starch and lipid levels. When dietary lipid level was 5%, fish fed the diet containing 30% wheat starch level had significantly higher hepatic glycogen content than those fed the 10% and 20% wheat starch diets; while, fish fed the diet containing 10% wheat starch had higher glycogen content in muscle than those fed the diets containing 20% and 30% wheat starch levels. When the dietary lipid level was 10%, fish fed 10% wheat starch level had significantly higher hepatic glycogen content than those fed 20% and 30% wheat starch diets; fish fed 30% wheat starch level had significantly higher glycogen content in muscle than those fed 10% and 20% wheat starch diets. Glutamic-pyruvic transaminase (ALT), glutamic-oxalacetic transaminase (AST), total cholesterol (TC) and glucose (GLU) were not significantly influenced by dietary wheat starch and lipid levels. However, total protein (TP) and triglyceride (TG) were significantly influenced by different dietary wheat starch and lipid levels. Lipase activity was significantly influenced by dietary wheat starch and lipid levels, when the dietary lipid level was the same, the lipase activity increased significantly with the increase of wheat starch level; fish fed the diet containing 10% lipid level had higher lipase activity than fish fed the 5% lipid level diet. The interaction of dietary wheat starch and lipid levels had significant effects on pyruvate kinase (PK), while there were no significant effects on activities of glucokinase (GK), phosphofructokinase (PFK), phosphoenolpyruvate carboxykinase (PEPCK), fructose-1,6-bisphosphatase (FBPase) and glucose-6-phosphatase (G6Pase). The results showed that when the dietary lipid level was 5%, large yellow croaker had the ability to maintain blood glucose content by adjusting the hepatic glycolysis key enzymes activities with increase of wheat starch supplemental level.