ABSTRACT

1. An in vitro test to study the effect of pH reduction on phytic acid degradation over time for four commercial phytases was conducted. Changing the pH level affected phytate degradation over time differently for the various phytases (P < 0.05).

2. The phytase with the largest response of pH reduction in the in vitro test and a feed pH level of 4.5 was chosen for the broiler experiment. The effect of intermittent feeding, addition of 500 FYT C. braakii-derived phytase and 1% formic acid were tested in a 2 x 2 x 2 factorial arrangement. Ten pens containing 10 birds each were fed each of the treatment combinations from 15 to 36 d of age. Ad libitum fed birds had two 4-h dark periods with 2-h light in-between, while intermittently fed birds in addition had restricted access to the feed through except for four 1-h and one 2-h feeding bouts.

3. In addition to assessing performance, excreta were collected on a pen basis. The tibia and contents from jejunum and ileum were collected from one bird per pen. In addition, crop contents were collected from the intermittently fed birds 80, 160 and 240 min after the start of feeding.

4. Phytase improved performance, ileal and jejunal P digestibility, P retention and tibia ash and P concentration (P < 0.001). Intermittent feeding increased jejunal P digestibility and P retention (P < 0.001), but ileal P digestibility increased only in the intermittently fed birds compared to the ad libitum fed birds without phytase addition (P = 0.025). Acidification increased jejunal P digestibility only in the ad libitum fed birds (P = 0.019). There was a considerable inositol hexakisphosphate degradation into lower isomers in the crop after 80 min for diets with phytase (InsP_{3 and 4}:P < 0.001), and acidification further increased this degradation (InsP₄:P = 0.007). After 160 min retention time, the effect of phytase and acidification was even higher with more significant (P < 0.05) interactions.

5. The current data showed that prolonged retention time in the crop combined with feed acidification increased phytase efficacy by improving the phytate degradation.

摘要

1.进行了一项体外试验，研究了四种商业肌醇六磷酸酶随着时间的推移，pH降低对肌醇六磷酸降解的影响。改变pH值对各种肌醇六磷酸酶随时间的变化对肌醇六磷酸降解的影响不同（P <0.05）。

2.在肉仔鸡实验中，选择了在体外试验中pH降低响应最大，饲料pH值为4.5的植酸酶。在2 x 2 x 2因子布置中测试了间歇喂食，添加500株FYT腕氏梭菌来源的植酸酶和1％甲酸的效果。从15到36天的年龄，分别给10只钢笔喂食10只家禽。随意喂食的家禽有两个4小时的黑暗时段，中间有2h的光照，而间歇喂食的家禽除了四个1h和一个2h的喂食回合之外，还限制了饲料的通过。

3.除了评估表现外，还以笔的形式收集排泄物。每只笔从一只鸟收集胫骨以及空肠和回肠的内容物。此外，在开始喂食80、160和240分钟后，从间歇喂食的家禽中收集农作物内容。

4.植酸酶改善了性能，回肠和空肠的P消化率，P保留率，胫骨灰分和P浓度（P <0.001）。间歇喂养增加了空肠磷的消化率和磷保留率（P <0.001），但回肠磷消化率仅与不添加肌醇六磷酸酶的随意喂养鸡相比有所增加（P = 0.025）。酸化仅在随意喂养的家禽中提高了空肠磷的消化率（P = 0.019）。植酸酶饮食（InsP _3和4：P <0.001）后80分钟后，作物中的肌醇六磷酸磷酸酯大量降解为较低的异构体，而酸化进一步加剧了这种降解（InsP ₄：P ＝ 0.007）。保留160分钟后，植酸酶和酸化的效果更高，相互作用更显着（P <0.05）。

5.当前数据表明，延长作物保留时间与饲料酸化相结合，可通过改善肌醇六磷酸的降解来提高肌醇六磷酸的功效。