Van der Klis J D, Versteegh H A, Simons P C, Kies A K
Institute for Animal Science and Health (ID-DLO), Lelystad, The Netherlands.
Poult Sci. 1997 Nov;76(11):1535-42. doi: 10.1093/ps/76.11.1535.
Microbial phytase hydrolyzes poorly degradable vegetable phytate P in the gastrointestinal tract of poultry; thereby increasing the availability of organic P to an extent that remains to be established. For this purpose, the P equivalency value of phytase in corn-soybean meal layer diets was assessed in three experiments (two short-term absorption studies and one performance trial lasting a complete production period). In the first absorption study, two basal diets containing 30 or 40 g Ca/kg diet were supplemented with either phytase [0, 250, or 500 phytase units (FTU)/kg diet] or with monocalcium phosphate (MCP; 0, 0.5, or 1.0 g P/kg diet) and fed to layers from 20 to 24 wk of age. The ileal absorption of Ca and P was measured during the last week. It was shown that 250 FTU/kg diet hydrolyzed an amount of phytate P that was equivalent to 1.3 g P from MCP. At the highest phytase inclusion level (500 FTU/ kg diet), a lower value of equivalency was observed, as P absorption was almost maximal at the lower level of phytase inclusion (250 FTU/kg diet). Phytase hydrolyzed phytate-bound P effectively at both Ca levels, although this degradation was significantly reduced by 12 percentage units at the higher dietary Ca level. The second absorption study, used 0, 250, and 500 FTU phytase/kg diet and 0 and 1.0 g P/kg diet of MCP. All diets were standardized at 35 g Ca/kg diet. The ileal absorption of Ca and P was determined at 24 and 36 wk of age. These values were significantly reduced in 36-wk-old hens compared to 24-wk-old hens. At 24 wk of age, phytic acid P degradation was significantly improved with increasing levels of phytase up to the maximum inclusion level of 500 FTU/kg diet (maximum phytic acid-P degradation at the end of the small intestine was 66%). In this experiment, the dose of 250 FTU/kg diet was equivalent to 0.8 g MCP-P. In Experiment 3, either phytase or MCP-P was added to a corn-soybean meal layer diet, containing 40 g Ca/kg diet and 3.6 g P/kg diet, at levels of 0, 100, 200, and 300 FTU/kg or levels of 0, 0.3, 0.6, and 0.9 g MCP-P/kg, respectively. Production performance was measured from 18 to 68 wk of age. Diets were consumed ad libitum. Growth, production performances (except kilograms of feed per kilogram of egg), and tibia parameters were significantly improved by dietary supplementation of the negative control diet with either phytase or MCP-P. Growth, egg production, and feed conversion ratio of the hens from the supplemented groups remained good throughout the experiment. No phytase dose effects on the production characteristics or tibia parameters were observed, indicating that the P requirements of the laying hens were met throughout the production period even at the lowest level of supplementation.
微生物植酸酶可水解家禽胃肠道中难降解的植物肌醇六磷酸磷；从而在一定程度上提高有机磷的利用率，不过该程度仍有待确定。为此，在三项试验（两项短期吸收研究和一项涵盖整个生产周期的生产性能试验）中评估了玉米 - 豆粕蛋鸡日粮中植酸酶的磷等效值。在第一项吸收研究中，两种分别含有30或40 g钙/千克日粮的基础日粮，添加了植酸酶[0、250或500植酸酶单位（FTU）/千克日粮]或磷酸二氢钙（MCP；0、0.5或1.0 g磷/千克日粮），并饲喂20至24周龄的蛋鸡。在最后一周测定钙和磷的回肠吸收率。结果表明，250 FTU/千克日粮水解的肌醇六磷酸磷量相当于1.3 g来自MCP的磷。在最高植酸酶添加水平（500 FTU/千克日粮）时，观察到等效值较低，因为在较低植酸酶添加水平（250 FTU/千克日粮）时磷吸收几乎已达最大值。在两种钙水平下，植酸酶均能有效水解与肌醇六磷酸结合的磷，尽管在较高日粮钙水平下这种降解显著降低了12个百分点。第二项吸收研究使用了0、250和500 FTU植酸酶/千克日粮以及0和1.0 g磷/千克日粮的MCP。所有日粮的钙含量均标准化为35 g/千克日粮。在24和36周龄时测定钙和磷的回肠吸收率。与24周龄的母鸡相比，36周龄母鸡的这些值显著降低。在24周龄时，随着植酸酶水平增加至最大添加水平500 FTU/千克日粮，植酸磷降解显著改善（小肠末端最大植酸磷降解率为66%）。在本试验中，250 FTU/千克日粮的剂量相当于0.8 g MCP - P。在试验3中，分别以0、100、200和300 FTU/千克或0、0.3、0.6和0.9 g MCP - P/千克水平，向含有40 g钙/千克日粮和3.6 g磷/千克日粮的玉米 - 豆粕蛋鸡日粮中添加植酸酶或MCP - P。测定18至68周龄的生产性能。日粮自由采食。通过在阴性对照日粮中添加植酸酶或MCP - P，生长、生产性能（除每千克蛋的饲料千克数外）和胫骨参数均显著改善。在整个试验过程中，添加组母鸡的生长、产蛋量和饲料转化率均保持良好。未观察到植酸酶剂量对生产特性或胫骨参数的影响，表明即使在最低添加水平下，整个生产周期内蛋鸡的磷需求也得到了满足。
