饲料中糖/脂肪比例对瓦氏黄颡鱼生长、饲料利用、血糖水平和肝脏糖酵解酶活力的影响

以初始体重(4.20±0.02)g的瓦氏黄颡鱼(Pelteobagrus vachelli)幼鱼为实验对象,在流水系统中进行为期8周的摄食生长实验,探讨饲料中糖与脂肪比例(CHO∶L)对其生长、饲料利用、血糖水平和糖酵解酶活力的影响。饲料等氮(粗蛋白40%)等能(19 MJ/g),CHO∶L梯度为0.75—6.53。每种饲料随机投喂3桶鱼,每桶(50 L)放养40尾鱼。实验结果表明随着CHO∶L升高,瓦氏黄颡鱼特定生长率(SGR)先升高后降低,当CHO∶L为3.55时,SGR达最大,显著高于CHO∶L为0.75和6.53时的值(P<0.05)。饲料效率(FE)和蛋白效率(PER)在CHO∶L为1.30—3.55区间内都没有显著差异,但当CHO∶L为0.75或6.53时,FE和PER的值都显著降低(P<0.05)。脏体比(VSI)、肝体比(HSI)在各处理组间无显差异(P>0.05)。随CHO∶L的增加,全鱼粗蛋白含量先增加后降低,且在CHO:L为3.55时达到最大值,且显著高于CHO:L为0.75时的值(P<0.05)。而全鱼粗脂肪含量随CHO∶L增加而显著减少(P<0.05)。血糖和血浆总胆固醇水平在各处理组间无显著差异(P>0.05),而血浆甘油三酯水平随CHO∶L的增加而显著增加(P<0.05)。随CHO∶L的增加,瓦氏黄颡鱼肝脏葡萄糖激酶(GK)活力先增加后降低,且在CHO∶L为3.55时活力最大,显著高于CHO∶L为0.75时的值(P<0.05)。肝脏己糖激酶(HK)、丙酮酸激酶(PK)和磷酸果糖激酶(PFK-1)活力在各处理组间没有显著差异(P>0.05)。用二次多项回归模型拟合特定生长率和CHO∶L的关系,得到饲料最适CHO∶L为4.06。

EFFECTS OF DIETARY CARBOHYDRATE TO LIPID RATIO ON GROWTH,FEED UTILIZATION, PLASMA GLUCOSE AND GLYCOLYTIC ENZYME ACTIVITIES OF JUVENILE DARKBARBEL CATFISH,PELTEOBAGRUS VACHELLI

An 8-week feeding trial was conducted to evaluate the effects of dietary carbohydrate-to-lipid(CHO︰L) ratio on growth performance,feed utilization,plasma glucose and key glycolytic enzyme activities of juvenile darkbarbel catfish(Pelteobagrus vachelli).Five isonitrogenous(crude protein 40%) and isoenergetic(19 MJ/g) diets were formulated to contain with graded levels of CHO︰L ratios(0.75—6.53).Each diet was randomly assigned to triplicate tanks(50 L),and each tank was stocked with 40 fish with initial body weight of(4.20±0.02) g.The specific growth rate(SGR) increased first and then decreased with the increasing dietary CHO︰L,and reached to the highest in fish fed diets with CHO︰L of 3.55,which was significantly higher than those of fish fed the diets with 0.75 and 6.53 ratios(P<0.05).Feed efficiency(FE) and protein efficiency ratio(PER) showed no significant difference among treatments with CHO︰L of 1.30—3.55,but FE and PER significantly decreased at CHO︰L of 0.75 and 6.53 respectively(P<0.05).No significant difference was observed in the HSI and VSI of the darkbarbel catfish among dietary treatments(P>0.05).The crude protein of fish whole body increased first and then decreased with the increasing dietary CHO︰L,and reached to the highest in fish fed diets with CHO︰L of 3.55,which was significantly higher than that at CHO︰L of 0.75(P<0.05).The crude lipid of fish whole body decreased with the increasing dietary CHO︰L significantly(P<0.05).There was no significant difference in the plasma glucose and total cholesterol among dietary treatments(P>0.05).Plasma triglycercide concentrations increased significantly with the increasing dietary CHO︰L(P<0.05).Hepatic glucokinase(GK) activities increased first and then decreased with the increasing dietary CHO︰L,and reached to the highest at the CHO︰L of 3.55,which was significantly higher than those at CHO︰L of 0.75(P<0.05).However,no significant difference was observed in activities of hepatic hexokinase(HK),pyruvate kinase(PK) and 6-phosphofructo-1-kinase activity(PFK-1) among dietary treatments(P>0.05).Based on second-order polynomial regression analysis of SGR against dietary CHO︰L ratios,a CHO︰L ratio of 4.06 was proved to be optimal for the growth of juvenile darkbarbel catfish.