Denbow D M, Ravindran V, Kornegay E T, Yi Z, Hulet R M
Department of Animal and Poultry Sciences, Virginia Polytechnic Institute, Blacksburg 24061-0306, USA.
Poult Sci. 1995 Nov;74(11):1831-42. doi: 10.3382/ps.0741831.
A 21-d experiment was conducted with day-old male broilers (n=840) to evaluate the effectiveness of supplemental phytase for improving the availability of phytate P in soybean meal when varying levels of P were fed. The semi-purified basal diet (.18% phytate P) contained soybean meal as the only protein source. Seven levels of phytase (0, 200, 400, 600, 800, 1,000, and 1,200 U/kg diet) were added to diets formulated to contain .20, .27, or .34% nonphytate P (nP; or .38, .45, and .52% total P, respectively). The desired levels of nP in the three basal P diets were achieved by adding varying amounts of defluorinated phosphate. A 2:1 Ca:total P ratio was maintained in all diets. Body weight gains and feed intake were improved (P < .001) by phytase at all nP levels, but the magnitude of response was greatest at low nP levels, resulting in an nP by phytase interaction (P < .01). Gain:feed was unaffected by phytase addition. A high mortality (35 to 45%) was observed for the .20 and .27% nP diets without added phytase, but this declined to normal levels with the addition of 200 to 400 U phytase/kg diet. Ash percentage of toes and tibia and shear force and stress of tibia increased with added phytase. These responses clearly show that the phytate-bound P in soybean meal was made more available to broilers by microbial phytase, and the total response was related to the phytase and nP/total P levels. Based on the high R2 values for the second order translog equations, BW gain, feed intake, and toe ash percentage were the most sensitive indicators to assess P availability, followed by tibia force and ash percentage. Derived nonlinear and linear equations for BW gain and toe ash percentage at the two lower nP levels were used to calculate P equivalency values of phytase for inorganic P. Using the average function of P released ( gamma ) by microbial phytase ( chi ) derived with nP levels of .20 and .27% for BW gain and toe ash percentage, gamma = 1.120 - 1.102e-.0027chi, 1 g of P could be released with 821 U of phytase. The amount of P released increased with increasing levels of phytase, but the amount of P released per 100 U of phytase decreased. Released P ranged from 31 to 58% of phytate P for 250 to 1,000 U of phytase/kg of diet.
以1日龄雄性肉鸡（n = 840）进行了一项为期21天的试验，以评估在饲喂不同磷水平时，添加植酸酶提高豆粕中植酸磷利用率的效果。半纯化基础日粮（植酸磷含量为0.18%）以豆粕作为唯一蛋白质来源。在配制的日粮中添加7个水平的植酸酶（0、200、400、600、800、1000和1200 U/kg日粮），日粮中有效磷（nP）含量分别为0.20%、0.27%或0.34%（总磷分别为0.38%、0.45%和0.52%）。通过添加不同量的脱氟磷酸盐，使三种基础磷日粮达到所需的有效磷水平。所有日粮中钙与总磷的比例维持在2:1。在所有有效磷水平下，添加植酸酶均能提高体重增加和采食量（P < 0.001），但在低有效磷水平下反应幅度最大，导致有效磷与植酸酶存在交互作用（P < 0.01）。添加植酸酶对料重比无影响。未添加植酸酶的0.20%和0.27%有效磷日粮出现了较高的死亡率（35%至45%），但添加200至400 U/kg日粮的植酸酶后死亡率降至正常水平。添加植酸酶后，脚趾和胫骨的灰分百分比以及胫骨的剪切力和应力增加。这些反应清楚地表明，微生物植酸酶使豆粕中与植酸结合的磷对肉鸡更易利用，总体反应与植酸酶和有效磷/总磷水平有关。基于二阶超越对数方程的高R²值，体重增加、采食量和脚趾灰分百分比是评估磷利用率最敏感的指标，其次是胫骨强度和灰分百分比。利用在两个较低有效磷水平下体重增加和脚趾灰分百分比的非线性和线性方程，计算植酸酶对无机磷的磷当量值。使用在有效磷水平为0.20%和0.27%时，根据体重增加和脚趾灰分百分比得出的微生物植酸酶释放磷（γ）的平均函数，γ = 1.120 - 1.102e-.0027χ，8旦1 U的植酸酶可释放1 g磷。释放的磷量随植酸酶水平的增加而增加，但每100 U植酸酶释放的磷量减少。对于250至1000 U/kg日粮的植酸酶，释放的磷占植酸磷的31%至58%。
