We conducted an 8-week feeding experiment by designing6 kinds of feed (addition levels of betaine: 0, 0. 05% , 0. 10% , 0. 20% , 0. 30% , 0. 40% ) to investigate the effects of dietary supplementation of betaine on the growth, nutritional components, serum biochemistry and enzyme activity on liver of juvenile Rachycentron canadum. The results show that when the addition level is 0.05% , the weight gain (WG) and specific growth rate (SGR) reach the maximum; the condition of liver is the best; the protein content is the highest in both whole body and muscle. When the addition level is higher than 0. 20% , the condition factor (CF) shows a negative correlation with the level of dietary betaine. Hepatasomatic index ( HSI) of each group is significantly lower than that of the control ( P<0. 05), and the lipid mass fraction (except forO. 10% group) is lower than that of the control. The concentration of tri-glyceride (TC) in serum is higher than that of the control, showing an "increase-decrease" trend. The activity of glutamic-pyruvie Iransaminase ( GPT) of all groups are significantly lower than that of the control (P <0.05). The results indicate that dietary supplementation of betaine can improve the growth and lipid metabolism for R. canadum, doing good to reduce the lipid of the fish.%通过8周的养殖试验,评估了饲料中添加甜菜碱对军曹鱼(Rachycentron canadum)生长、体营养成分、血清生化指标和肝脏中酶活性的影响.共设计6种饲料,甜菜碱添加水平分别为0、0.05％、0.10％、0.20％、0.30％和0.40％.结果显示,添加水平为0.05％时增重率(WG)和特定生长率(SGR)最高,肝脏组织状况最好,全鱼和肌肉中蛋白质质量分数最高；添加水平超过0.20％时肥满度(CF)随甜菜碱添加量的上升而下降.各添加组的肝体比(HSI)均显著低于对照组且全鱼和肝脏中(0.10％添加组除外)的脂肪质量分数均低于对照组；血清指标中各添加组的血清甘油三酯(TG)浓度均高于对照组,但随着添加量的提高有先升后降的趋势；肝脏中谷丙转氨酶(GPT)的活性显著低于对照组.由此可见,饲料中添加适量的甜菜碱可以促进军曹鱼的生长,具有一定的降脂作用,利于脂肪代谢.
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