Department of Animal Health and Bioscience, Faculty of Agricultural Sciences, Aarhus University, PO Box 50, 8830 Tjele, Denmark.
J Dairy Sci. 2011 Feb;94(2):951-9. doi: 10.3168/jds.2010-3504.
Three in vitro experiments using a rumen fluid buffer system were performed to investigate the effect of addition of 4 experimental phytases (Phy1, Phy2, Phy3, and Phy4) compared with no addition of phytase on feed inositol phosphate hydrolysis in wheat and rapeseed cake to determine which of the 4 phytases was most suitable under rumen-like conditions. The feedstuffs were incubated with a mixture of physiological buffer, ruminal fluid, and exogenous phytase at pH 6.2, after which the samples were incubated for different periods. Incubations were stopped using HCl, and the samples were analyzed for inositol phosphates via high performance ion chromatography. Addition of phytase (Phy1) resulted in enhanced degradation of myo-inositol hexakisphosphate (InsP(6)) in rapeseed cake, whereas addition of exogenous phytase did not improve the degradation of InsP(6) in wheat. Only rapeseed cake was therefore used subsequently. All 4 phytases increased degradation of InsP(6) in rapeseed cake in the in vitro system, and degradability of InsP(6) increased with higher incubation time and higher phytase dosages, independent of phytase. Addition of 2 units of phytase per gram of substrate of the phytases Phy1, Phy2, Phy3, and Phy4 led to an undegraded InsP(6) content of 56, 49, 70, and 18%, respectively, when incubated with rapeseed cake for 6h, indicating that Phy2 and Phy4 were the most effective phytases. However, Phy2 had a higher specific activity than Phy4, as 60% of the original InsP(6) content was remaining after 3h when 5mg of enzyme protein per gram of substrate of Phy2 was added to rapeseed cake, whereas 150 mg of enzyme protein per gram of substrate of Phy4 was necessary to achieve a similar result. Therefore, Phy2 appeared to be most applicable under rumen-like conditions.
进行了三项体外实验，使用瘤胃液缓冲体系，研究了添加 4 种实验植酸酶（Phy1、Phy2、Phy3 和 Phy4）与不添加植酸酶相比，对小麦和菜籽饼中饲料肌醇六磷酸水解的影响，以确定在类似瘤胃条件下哪种植酸酶最适用。在 pH6.2 下，用生理缓冲液、瘤胃液和外源性植酸酶混合物孵育饲料，然后在不同时间点孵育样品。使用 HCl 停止孵育，通过高效离子色谱法分析样品中的肌醇磷酸。添加植酸酶（Phy1）可增强菜籽饼中肌醇六磷酸（InsP(6)）的降解，而添加外源性植酸酶并不能提高小麦中 InsP(6)的降解。因此，仅随后使用菜籽饼。在体外系统中，所有 4 种植酸酶均增加了菜籽饼中 InsP(6)的降解，InsP(6)的降解率随着孵育时间的延长和植酸酶剂量的增加而增加，而与植酸酶无关。添加每克底物 2 个单位的植酸酶 Phy1、Phy2、Phy3 和 Phy4，在 6 小时孵育菜籽饼时，未降解的 InsP(6)含量分别为 56%、49%、70%和 18%，表明 Phy2 和 Phy4 是最有效的植酸酶。然而，Phy2 的比活度高于 Phy4，当每克底物添加 5mg 酶蛋白时，Phy2 中 60%的原始 InsP(6)含量在 3 小时后仍保留，而添加 Phy4 时则需要 150mg 酶蛋白/克底物才能达到类似的效果。因此，Phy2 似乎在类似瘤胃的条件下最适用。
