Kornegay E T, Qian H
Department of Animal and Poultry Sciences, Virginia Polytechnic Institute and State University, Blacksburg 24061-0306, USA.
Br J Nutr. 1996 Oct;76(4):563-78. doi: 10.1079/bjn19960063.
Ninety-six crossbred young pigs (body weight 7.8 kg) were used in a 5-week trial to determine the effectiveness of microbial phytase (EC 3.1.3 26) in improving the bioavailabilities of P and other nutrients in maize-soyabean-meal diets and, thus, replacing inorganic P with phytase. A 2 x 5 factorial arrangement of treatments was employed with two available P (aP) levels (0.7 and 1.6 g/kg) and five phytase levels (0, 350, 700, 1050, 1400 U (the quantity of enzyme that liberates 1 mumol inorganic phosphate/min from 5.1 mm-sodium phytate at pH 5.5 and 37 degrees)/kg diet). In addition, two extra diets were formulated to supply the National Research Council (1988) recommended level of aP (3.2 g/kg) with 0 or 1400 U phytase. The addition of graded levels of phytase resulted in linear increases in average daily weight gain, average daily feed intake and weight gain:feed intake for pigs fed on diets containing 0.7 or 1.6 g aP/kg (P < 0.04). Also, the addition of phytase linearly increased apparent digestibilities of P and Ca (P < 0.01), whereas faecal P excretion was linearly decreased (P < 0.01). Linear increases in shear force, shear energy and ash content of both the metacarpal and tenth rib, and shear stress of the metacarpal were found to respond to added phytase (P < 0.01). These improvements in performance, apparent P absorption and bone measurements by phytase were also observed by increasing dietary aP levels for most measurements. Adding 1400 U phytase to the 3.2 g aP/kg diet further increased average daily weight gain, average daily feed intake, apparent absorption of P, Ca and N and metatarsal shear force and ash content (P < 0.01 to 0.05). Generally, maximum responses occurred at a phytase level of 1050 U/kg diet for the 0.7 g aP/kg diets and 700 U for the 1.6 g aP/kg diets. Based on non-linear and linear response equations generated for the phytase and aP levels, the average function of the equivalency of P (Y, g/kg) v. microbial phytase (X, U/kg) was developed across aP levels of 0.7 and 1.6 g/kg for average daily weight gain and apparent digestibility of P: Y = 2.622-2.559e 0.00185X. The replacement of 1 g inorganic P as defluorinated phosphate would require about 246 U microbial phytase. This represents 41% of released P from phytate.
96头杂交幼猪（体重7.8千克）用于一项为期5周的试验，以确定微生物植酸酶（EC 3.1.3 26）在提高玉米 - 豆粕型日粮中磷及其他养分的生物利用率从而用植酸酶替代无机磷方面的效果。试验采用2×5析因处理设计，有两个有效磷（aP）水平（0.7和1.6克/千克）和五个植酸酶水平（0、350、700、1050、1400酶活性单位（在pH 5.5和37℃条件下，每分钟从5.1毫摩尔肌醇六磷酸钠中释放1微摩尔无机磷酸盐的酶量）/千克日粮）。此外，还配制了两种额外日粮，分别提供美国国家研究委员会（1988年）推荐水平的aP（3.2克/千克），一种添加0单位植酸酶，另一种添加1400单位植酸酶。添加不同水平的植酸酶使平均日增重、平均日采食量和增重：采食量呈线性增加，对采食含0.7或1.6克aP/千克日粮的猪而言（P<0.04）。同时，添加植酸酶使磷和钙的表观消化率呈线性增加（P<0.01），而粪磷排泄量呈线性下降（P<0.01）。发现掌骨和第十肋骨的剪切力、剪切能和灰分含量以及掌骨的剪切应力对添加植酸酶呈线性增加（P<0.01）。对于大多数测定指标，通过提高日粮aP水平也观察到植酸酶在性能、表观磷吸收和骨骼指标方面的这些改善。在含3.2克aP/千克日粮中添加1400单位植酸酶进一步提高了平均日增重、平均日采食量、磷、钙和氮的表观吸收率以及跖骨剪切力和灰分含量（P<0.01至0.05）。一般来说，对于含0.7克aP/千克的日粮，植酸酶水平为1050单位/千克时出现最大反应；对于含1.6克aP/千克的日粮，植酸酶水平为700单位时出现最大反应。基于为植酸酶和aP水平生成的非线性和线性反应方程，针对平均日增重和磷的表观消化率，在0.7和1.6克/千克的aP水平上建立了磷（Y，克/千克）与微生物植酸酶（X，单位/千克）等效性的平均函数：Y = 2.622 - 2.559e^(-0.00185X)。替代1克作为脱氟磷酸盐的无机磷大约需要246单位微生物植酸酶。这相当于从植酸盐中释放磷的41%。
