植酸酶对草鱼和新吉富罗非鱼消化酶活性的影响

Effect of Plant-Based Diets Supplemented with Phytase on Digestive Enzyme Activities in Grass Carp and NEW GIFT Nile Tilapia

植酸酶能水解植酸络合物,释放被植酸束缚的各种营养因子,因此能有效解除植酸与内源性消化酶的结合,促进消化酶的作用。本实验在全植物性饲料中添加植酸酶,研究其对草鱼(Ctenopharyngodon idellus)和新吉富罗非鱼(Oreochromis niloticus)淀粉酶及蛋白酶比活力的影响。以全植物性饲料为阴性对照组,添加磷酸氢钙(dibasic calcium phosphate,DCP)实验组为阳性对照组,另设4个不同梯度的植酸酶实验组(250 U/kg、500 U/kg、1 000 U/kg和2 000 U/kg)。实验选取健壮、规格齐整平均体质量为(12.59±0.09)g的草鱼和平均体质量为(9.59±0.12)g的新吉富罗非鱼,分别随机分为6个组,每组5个平行,每个平行20尾鱼。养殖8周后,草鱼平均体质量(18.29±0.63)g,新吉富罗非鱼平均体质量为(24.68±1.34)g,抽样取出胃、肠和肝胰脏用来分析淀粉酶和蛋白酶比活力。结果表明,植酸酶对无胃鱼草鱼和有胃鱼罗非鱼淀粉酶及蛋白酶比活力都有显著的促进作用。相比较而言,植酸酶对罗非鱼的应用效果较明显,低剂量就能显著提高其淀粉酶及蛋白酶比活力(P<0.05)。当植酸酶添加量达到1 000 U/kg时,草鱼和罗非鱼淀粉酶及蛋白酶比活力均达到峰值,此时,罗非鱼淀粉酶和蛋白酶比活力与阳性对照组无显著差异(P>0.05),而草鱼肝胰脏蛋白酶比活力显著高于阳性对照组(P<0.05)。植酸酶2 000 U/kg实验组,罗非鱼淀粉酶和蛋白酶比活力与1 000 U/kg植酸酶实验组无显著差异(P>0.05),但草鱼肝胰脏蛋白酶比活力显著低于1 000 U/kg植酸酶实验组(P<0.05)。因此,本实验条件下,植酸酶在草鱼和新吉富罗非鱼全植物性蛋白质配合饲料中的适宜添加量均为1 000 U/kg,生产实践中可通过添加植酸酶部分替代无机磷源。

Phytase could enhance the activity of digestive enzymes because it could hydrolyze the salts of phytic acid to release nutritional factors chelated by phytic acid, and eliminate the combination of phytic acid and endogenous digestive enzymes. The experiments were conducted to evaluate the effects of phytase on protease and amylase activities in Grass Carp （Ctenopharyngodon idellus） and NEW GIFT Nile Tilapia （Oreochromis niloticus） by feeding with plant-based diets supplemented with graded levels of phytase. Six isonitrogenous and isocaloric diets were formulated： two control diets （negative control diet： plant-based without calcium phosphate dibasic （DCP） and phytase added, and positive control diet with DCP added but without phytase）, and the other four experimental diets with graded levels of phytase （250, 500, 1 000, 2 000 U/kg）. Grass Carp of robust and uniform size with body weight 12.590.09 g and NEW GIFT Nile Tilapia with body weight 9.590.12 g were randomly divided into six groups respectively, 5 replicates per treatment with 20 fish. After 56 days breeding experiments, body weight of Grass Carp and NEW GIFT Nile Tilapia reached 18.290.63 g and 24.681.34 g, respectively. The stomach, hepatopancreas and intestine were randomly taken for analysis of endogenous protease and amylase activities. The results showed that in no-stomach fish like Grass Carp and gastric fish like Tilapia, endogenous protease and amylase activities were significantly enhanced by dietary phytase. By comparison, the sound effect of phytase in tilapia was more obvious, for the protease and amylase activities were improved remarkably by phytase at a low level of 250 U/kg for tilapia （P〈0.05）. Activities of these two digestive enzymes in Grass Carp and Tilapia tissues reached the maximum value at the level of 1 000 U/kg, while in Tilapia the enzyme activity values were not markedly different from those of the positive control （P〉0.05）.The protease activity in hepatopancreas of Grass Carp in 1 000 U/kg phytase group was significantly higher than that of positive control （P〈0.05）. In addition, the protease and amylase activities of Tilapia in 2 000 U/kg group was not significantly different from that of 1 000 U/kg group, while the protease activity of hepatopancreas in Grass Carp was significantly declined （P〈0.05）. Consequently, the optimum phytase amount in manufactured feed was 1 000 U/kg not only for NEW GIFT Nile Tilapia but also for Grass Carp under the condition of this experiment. The phytase could be used to replace partly inorganic phosphorus sources in the fish feeding.