不同蛋白能量比饲料对草鱼幼鱼消化酶活性的影响

以鱼粉和豆粕为蛋白源,鱼油和豆油等比例混合油为脂肪源,共配制4个蛋白水平(20%、25%、30%、35%),每一蛋白水平设4个脂肪水平(4.5%、8%、11.5%、15%),共16组饲料。每组设3个重复,在水温23~29℃下,连续投喂初始体重为(16.84±0.28)g的草鱼(Ctenopharyngodon idellus)10周,研究不同蛋白能量比饲料对草鱼幼鱼消化酶活性的影响。结果显示:肠道蛋白酶的活性随着饲料蛋白含量的升高而显著升高(P<0.05),饲料蛋白水平在20%~30%时,饲料中的脂肪水平对蛋白酶活性影响不显著(P>0.05),蛋白水平在35%时,高脂肪抑制了蛋白酶活性,肝胰脏的蛋白酶变化规律类似于肠道;肠道和肝胰脏淀粉酶活性在饲料蛋白含量相同的情况下,随着脂肪含量的升高呈现显著的下降趋势(P<0.05),但饲料中蛋白(30%,35%)和脂肪(8%,11.5%,15%)含量较高时,淀粉酶活性较稳定;肠道和肝胰脏的脂肪酶活性在饲料蛋白含量相同的情况下,随着脂肪含量的升高,呈显著上升的趋势(P<0.05),但在蛋白含量(30%,35%)和脂肪含量(8%、11.5%,15%)的6个试验组之间差异不显著(P>0.05);在脂肪含量分别为4.5%、8%和11.5%时,饲料的蛋白含量对肠道的脂肪酶活性无显著性影响(P>0.05),当脂肪含量为15%时,随着蛋白含量的升高,肠道的脂肪酶活性显著降低(P<0.05)。结果表明,草鱼饲料中蛋白含量为30%和脂肪为8%(即蛋白能量比21.7 mg/kJ)的试验组草鱼获得较高的消化酶活性。

Effect of dietary protein-energy ratio on digestive enzyme activities of juvenile Ctenopharyngodon idellus

A 4 ×4 factorial experiment was performed to study the effects of protein-energy ratio on digestive enzyme activities of juvenile grass carp (Ctenopharyngodonidellus).Sixteen practical diets were formulated,containing increasing levels of protein(20%,25%,30%,and 35%) and four lipid levels (4.5%,8%,11.5% and 15%) within each protein level.The fish were fed daily to apparent satiation for 70 days with water temperature fluctuated from 23 ℃ to 29 ℃ during the experimental period.The results showed that,intestinal protease activity increased significantly with the increase of dietary protein content (P<0.05).The dietary lipid level did not significantly affect protease activity with dietary protein levels from 20% to 30%,while an increase of lipid level negatively affected protease activity at the 35% protein level.Hepatopancreas protease had a similar variation with the intestine.When the protein level was 20% and 25%,the amylase activities in intestine and hepatopancreas were decreased significantly with the increasing lipid levels(P<0.05),however,there was no significant difference at the higher protein levels (30%,35%) and higher lipid levels (8%,11.5%,15%);At the 20% and 25% protein levels,the lipase activitities in intestine and hepatopancreas were increased markedly with the increasing lipid levels(P<0.05),when the protein and lipid levels reached to 30%,35%and 8%,11.5%,15%,respectively,there was no significant difference in intestine and hepatopancreas lipase activities;when the lipid level is 4.5%,8% and 11.5%,the diet protein level had no significant effect on the intestinal lipase activity(P>0.05),however,the 15% lipid level negatively affected the intestinal lipase activity (P<0.05).These results suggested that the diet containing 30% protein and 8% lipid with P/E ration of 21.7 mg protein kJ-1 was optimum for juvenile grass carp to have the highest digestive enzyme activities.