不同脂肪和葡萄糖水平对大黄鱼生长性能、肝脏糖酵解和糖异生关键酶活性的影响

本试验旨在研究不同脂肪和葡萄糖水平对大黄鱼生长性能、肝脏糖酵解和糖异生关键酶活性、血清生化指标、糖原含量及消化酶活性等的影响。采用2×3双因素试验设计,其中脂肪设5%、10%2个水平,葡萄糖设10%、20%、30%3个水平,共配制6种试验饲料。每种饲料设3个重复,每个重复放养平均体重为(14.79±0.13)g的大黄鱼幼鱼50尾。试验期为8周。结果表明:饲料脂肪和葡萄糖水平的交互作用对大黄鱼增重率(WGR)、特定生长率(SGR)和饲料效率(FE)的影响不显著(P0.05)。在饲料脂肪水平为5%时,WGR和SGR随饲料葡萄糖水平增加而降低,30%葡萄糖组的WGR和SGR显著低于10%葡萄糖组(P0.05)。饲料脂肪和葡萄糖水平的交互作用对大黄鱼全鱼水分和粗脂肪含量的影响显著(P0.05),而对全鱼粗蛋白质含量无显著影响(P0.05)。饲料脂肪和葡萄糖水平的交互作用对大黄鱼肝糖原、肌糖原含量有显著影响(P0.05)。在饲料脂肪水平为5%时,肝糖原含量随饲料葡萄糖水平的升高而升高,而肌糖原含量随着饲料葡萄糖水平的升高先升高后降低;在饲料脂肪水平为10%时,肝糖原含量随饲料葡萄糖水平的升高先降低后升高,肌糖原含量随着饲料葡萄糖水平的升高而升高。饲料脂肪和葡萄糖水平的交互作用对大黄鱼血清总蛋白(TP)、总胆固醇(TC)、甘油三酯(TG)、葡萄糖含量及丙氨酸氨基转移酶(ALT)和天冬氨酸氨基转移酶(AST)活性无显著影响(P0.05);然而,在饲料脂肪水平相同时,血清葡萄糖含量随饲料葡萄糖水平的升高而升高,30%葡萄糖组血清葡萄糖含量显著高于10%葡萄糖组(P0.05)。饲料脂肪和葡萄糖水平的交互作用对大黄鱼肝脏葡萄糖激酶(GK)、磷酸果糖激酶(PFK)、磷酸烯醇式丙酮酸羧激酶(PEPCK)活性有显著影响(P0.05),而对丙酮酸激酶(PK)、1,6-二磷酸果糖酶(FBPase)、6-磷酸葡萄糖酶(G6 Pase)活性无显著影响(P0.05)。在饲料脂肪水平为10%时,随饲料葡萄糖水平的升高,肝脏GK、PFK活性升高,肝脏PEPCK活性先升高后降低。由结果可知,与饲料脂肪水平为10%时相比,在饲料脂肪水平为5%时,随饲料葡萄糖的水平的升高,大黄鱼能够通过调节糖代谢关键酶活性及肝糖原含量来维持血糖含量的平衡,有效利用饲料中的葡萄糖。综合本试验结果,建议大黄鱼幼鱼阶段饲料适宜的脂肪和糖水平分别为10%和20%。

Effects of Different Lipid and Glucose Levels on Growth Performance,Hepatic Glycolysis and Gluconeogenic Key Enzyme Activities of Large Yellow Croaker (Larmichthys crocea Richardson)

An 8-week feeding trial was conducted to evaluate the effects of different lipid and glucose levels on growth performance, hepatic glycolysis and gluconeogenic key enzyme activities, serum biochemical indices, glycogen contents and digestive enzyme activities etc. of large yellow croaker. Six experimental diets were for-mulated to contain two lipid levels ( 5% and 10%) and three glucose levels ( 10%, 20% and 30%) using 2 × 3 double-factor experimental design. Each diet was randomly assigned to 3 replicates of 50 juvenile large yellow croakers with the initial body weight of ( 14. 79 ± 0. 13 ) g. The results showed that weight gain rate ( WGR) , specific growth rate ( SGR) and feed efficiency ( FE) were not significantly affected by the interac-tion of dietary lipid and glucose levels (P>0.05). When the dietary lipid level was 5%, the WGR and SGR were decreased with the increase of dietary glucose level, which in 30% glucose group were significantly lower than those in 10% glucose group ( P<0.05) . The interaction of dietary lipid and glucose levels had significant effects on the contents of crude lipid and moisture of whole body ( P<0.05) , but had no significant effects on the content of crude protein of whole body ( P>0.05) . The contents of hepatic glycogen and muscle glycogen were significantly affected by the interaction of dietary lipid and glucose levels (P<0.05). When the dietary lipid level was 5%, hepatic glycogen content was increased with the dietary glucose level increasing, while the muscle glycogen content was firstly increased and then down. But when the dietary lipid level was 10%, hepat-ic glycogen content was firstly increased and then decreased with the dietary glucose level increasing, while the muscle glycogen content was increased. The interaction of dietary lipid and glucose levels did not have signifi-cant effects on the contents of total protein, total cholesterol, triglyceride, glucose and the activities of alanine aminotransferase and aspartate transaminase in serum of large yellow croaker (P>0.05). However, when the dietary lipid level was the same, serum glucose content had an increase trend with dietary glucose level increas-ing, and that in 30% glucose group was significantly higher than that in 10% glucose group ( P<0.05) . Hepat-ic glucokinase, phosphofructokinase and phosphoenolpyruvate carboxy kinase activities were significantly af-fected by the interaction of dietary lipid and glucose levels ( P<0.05) , while there were no significant effects on pyruvate kinase, glucose-6-phosphatase and fructose-1,6-bisphosphatase activities ( P>0.05) . When the di-etary lipid level was 10%, the hepatic glucokinase and phosphofructokinase activities were increased with dieta-ry glucose level increasing, while the hepatic phosphoenolpyruvate carboxy activity was firstly increased and then decreased. These results demonstrate that, compared with the dietary 10% lipid level, when the dietary lipid level is 5%, large yellow croaker has the ability to maintain the balance of blood glucose content by adjus-ting hepatic glycogen contents, glucose metabolism key enzyme activities and effectively utilizes glucose in di-ets with the dietary glucose level increasing. The results of present study indicate that the optimal requirements of lipid and carbohydrate for large yellow croaker in the larval stage are recommended to be 10% and 20%, re-spectively.