Phytase is of importance to the poultry industry because of its ability to hydrolyze phytate and release phosphorus (P) for use by poultry. However, the effect of age on phytase efficacy is not fully understood. A total of 864 day-old broiler chicks were used to investigate the effect of age and feeding length on phytase efficacy using growth performance, mineral utilization, and tibia ash as response criteria of evaluation. The experiment was arranged as a 3 × 2 × 2 factorial in a randomized complete block design with 3 diets including; a positive control (PC; 0.4% non-phytate P (nPP)), a negative control (NC; 0.2% nPP) and a NC diet supplemented with phytase at 2,000 FYT/kg; 2 ages (i.e., days 14 and 22); and 2 feeding lengths (i.e., 2 and 5 D) with 8 replicates each. Birds fed the NC had decreased (P < 0.01) body weight gain and feed efficiency compared with birds fed the PC regardless of age or feeding length. Similarly, birds fed the phytase-supplemented diet had improved (P < 0.01) performance as compared to birds fed the NC regardless of age. There were no significant differences in P utilization between birds fed for 2 to 14 D or 22 D and birds fed for 5 D to both ages. However, phytase was more efficacious at day 14 than day 22 when mineral utilization was considered because the super dose of phytase elicited greater response in birds fed the phytase supplemented diet for 2 D until day 14. In contrast, percentage tibia ash improved (P < 0.01) in birds fed phytase supplemented diet for 5 D at both ages as compared with birds fed for 2 D. In conclusion, testing phytase products, even at high doses, for 2 D during the second week in the life cycle of broiler chicks, can be recommended from the results of this study.

中文翻译：

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年龄和饲喂长度对肉鸡起始阶段植酸酶功效的影响。

植酸酶对家禽业很重要，因为它能够水解植酸盐并释放磷 (P) 供家禽使用。然而，年龄对植酸酶功效的影响尚不完全清楚。使用生长性能、矿物质利用和胫骨灰分作为评价的响应标准，共使用 864 日龄肉鸡研究年龄和饲喂长度对植酸酶功效的影响。实验安排为 3 × 2 × 2 因子，采用随机完全区组设计，包含 3 种饮食，包括：阳性对照（PC；0.4% 非植酸磷（nPP））、阴性对照（NC；0.2% nPP）和添加植酸酶 2,000 FYT/kg 的 NC 日粮；2 个年龄（即第 14 天和第 22 天）；和 2 个进料长度（即 2 和 5 D），每个进料 8 个重复。喂食 NC 的鸡只减少了（P < 0. 01) 与饲喂 PC 的鸡相比，无论年龄或饲喂长度如何，体重增加和饲料效率。类似地，与饲喂 NC 的鸡相比，饲喂添加植酸酶日粮的鸡的性能有所改善（P < 0.01），无论年龄大小。饲喂 2 至 14 日或 22 日的鸡和饲喂 5 日的鸡在两个年龄阶段的磷利用率没有显着差异。然而，当考虑矿物质利用时，植酸酶在第 14 天比第 22 天更有效，因为在第 14 天之前，超剂量植酸酶在饲喂植酸酶补充日粮 2 天的鸡中引起了更大的反应。相比之下，胫骨灰分百分比有所提高（P < 0.01) 与饲喂 2 天的禽类相比，饲喂 5 天的饲喂植酸酶日粮的禽类中的 0.01)。