不同碳水化合物和蛋白质水平膨化饲料对大规格草鱼生长、肠道消化酶及血清指标的影响

为探究不同碳水化合物和蛋白质水平膨化饲料对大规格草鱼生长、体成分、肠道消化酶和血清指标的影响,以初始体质量(398.6±5.9)g的大规格草鱼为研究对象,设置不同碳水化合物/蛋白质水平分别为C31P30、C34P28、C37P26、C40P24、C43P22、C46P20、C49P18的7组膨化饲料,养殖周期为16周。实验结果显示,各饲料组草鱼成活率(SR)差异不显著,随着蛋白质水平的下降、碳水化合物水平的升高,增重率(WGR)呈下降趋势,蛋白质效率(PER)呈升高趋势;肝体比(HSI)、脏体比(VSI)、肠体比(ISI)、肌肉和肝脏粗脂肪(CF)含量均有随饲料碳水化合物水平升高而升高的趋势。随着饲料中碳水化合物水平升高、蛋白质水平下降,各组间草鱼肌肉粗蛋白质(CP)含量无显著差异;肝糖原、肌糖原含量呈升高趋势,饲料中碳水化合物水平分别高于46%和40%时,肝糖原、肌糖原含量显著升高。肠道胰蛋白酶(PRS)和淀粉酶(AMS)活性随饲料中碳水化合物水平的升高呈先下降后升高趋势,脂肪酶(LPS)活性呈升高趋势;血清总胆固醇(TC)、甘油三酯(TG)、低密度脂蛋白(LDL)、高密度脂蛋白(HDL)含量及谷草转氨酶与丙转氨酶(GOT/GPT)比值都随饲料中碳水化合物水平升高和蛋白质水平下降而呈升高的趋势。本实验结果显示:当饲料碳水化合物水平高于37%、蛋白质水平低于26%时,将显著影响草鱼的生长,饲料中高碳水化合物水平将导致鱼体肝体比、脏体比、肠体比以及肌肉和肝脏脂肪含量升高。

Effects of different dietary carbohydrate and protein levels on growth, intestinal digestive enzymes and serum indexes in large-size grass carp (Ctenopharyngodon idella)

A 16-week feeding experiment was conducted to study the effects of different dietary carbohydrate and protein levels on growth, body composition, intestinal digestive enzyme activity and serum indexes of large-size grass carp (Ctenopharyngodon idella)initial body weight (398.6±5.9 g)]. Seven extruded diets with different levels of carbohydrate (C) and protein (P) (C31P30, C34P28, C37P26, C40P24, C43P22, C46P20, C49P18) were made. Experimental results showed that with protein levels decreasing and carbohydrate levels increasing, weight gain rate decreased significantly, protein efficiency significantly increased, hepatosmatic index, viscera index, intestinosomatic index and the fat content of muscle and liver increased significantly. However, the protein content in muscle had no significant difference among dietary treatments. The carbohydrate levels affected significantly the glycogen content in liver and muscle. The glycogen content in liver and muscle increased significantly when the carbohydrate levels were equal to or over 46% and 40%, respectively. The activities of intestinal trypsin and amylase decreased firstly, and then showed a tendency of increase, and lipase activity significantly increased. The content of serum total cholesterol (TC), triglyceride (TG), low density lipoprotein (LDL), high density lipoprotein (HDL), and glutamic-oxalacetic transaminase (GOT)/glutamic-pyruvic transaminase (GPT)values had a rising trend with dietary carbohydrate levels increasing and protein level decreasing. These results indicated that lower protein (protein levels below 26%) and higher carbohydrate (carbohydrate level above 37%) imposed a negative effect on growth performance, and the hepatosmatic index, viscera index, intestinosomatic index and the fat content of muscle and liver were significantly increased at high level of dietary carbohydrate.