Department of Animal Science, Iowa State University, Ames, IA 50011-1178.
Iowa Pork Industry Center, Iowa State University, Ames, IA 50011-1178.
J Anim Sci. 2021 Apr 1;99(4). doi: 10.1093/jas/skab001.
Previous research indicated that phytase may release less phosphorus (P) from phytate when it is evaluated using diets with P levels above requirement as compared with diets below requirement. The objectives of this experiment were to further test the hypothesis that the P release values determined for phytase are higher when pigs are fed diets that are deficient (DE) in P compared with when they are fed diets that are adequate (AD) in P, and that phytase will increase the digestibility of dry matter (DM), gross energy (GE), nitrogen (N), and calcium (Ca) independent of dietary P status. Twenty-four barrows (body weight: 23.2 ± 1.8 kg) were randomly assigned to one of eight dietary treatments and housed in individual pens for 21 d and then moved to metabolism crates for 9 d, with the collection of urine and feces occurring on the final 5 d. A basal corn-soybean meal diet (P-AD) was formulated at 0.36% standardized total tract digestible (STTD) P and total calcium:STTD P (Ca:STTD P) of 2:1. A P-DE diet was also formulated to maintain a constant Ca:STTD P of 2:1 in both basal diets. Phytase was added to AD and DE diets at 350, 600, 1,000 phytase units (FYT)/kg. Pig was the experimental unit; diet (P-AD or P-DE), phytase level, and replicate were fixed effects. Orthogonal polynomial contrasts were used to test linear and quadratic effects of phytase within P-AD and P-DE diets. Phytase improved apparent total tract digestibility (ATTD) and STTD of P in both P-AD (linear P < 0.001) and P-DE diets (quadratic P < 0.001). Estimates for STTD P release were 0.07%, 0.09%, and 0.09% for 350, 600, and 1,000 phytase units (FYT)/kg in P-DE diets, and 0.02%, 0.03%, and 0.05% in P-AD diets, respectively. In P-DE diets, phytase improved absorption and retention of P and increased urinary excretion of P (quadratic P < 0.001). In P-AD diets, phytase improved absorption of P (linear P = 0.066), tended to improve retention (linear P = 0.066), and increased urinary excretion of P (quadratic P = 0.021). Phytase improved ATTD of Ca in P-DE diets (quadratic P = 0.002) but not in P-AD diets (P > 0.1). In conclusion, the release of P by phytase is lower in diets that are AD in P than those which are DE. Phytase increased the availability of Ca only in the diets DE in P. Finally, phytase increased the ATTD of DM and tended to increase the ATTD of energy, independent of dietary P status.
先前的研究表明，与低磷（P）需求饮食相比，当用高磷需求饮食来评估植酸酶时，植酸酶从植酸盐中释放的磷（P）量可能会更少。本实验的目的是进一步验证以下假设，即在低磷（P）需求饮食中，与在充足（AD）磷需求饮食中相比，确定的植酸酶磷（P）释放值更高，并且植酸酶将提高干物质（DM）、总能量（GE）、氮（N）和钙（Ca）的消化率，而与日粮磷（P）状态无关。24 头阉公猪（体重：23.2±1.8kg）随机分配到 8 种日粮处理中的一种，并单独饲养 21 天，然后转移到代谢笼中饲养 9 天，最后 5 天收集尿液和粪便。基础玉米-豆粕日粮（P-AD）以 0.36%标准化总肠道可消化（STTD）磷和总钙：STTD 磷（Ca：STTD P）为 2:1 进行配制。还配制了低磷（P）日粮以保持基础日粮中 Ca：STTD P 恒定在 2:1。在 AD 和 DE 日粮中添加 350、600、1000 单位（FYT）/kg 的植酸酶。猪是实验单位；日粮（P-AD 或 P-DE）、植酸酶水平和重复是固定效应。使用正交多项式对比来测试 P-AD 和 P-DE 日粮中植酸酶的线性和二次效应。植酸酶提高了 P-AD（线性 P<0.001）和 P-DE 日粮（二次 P<0.001）中 P 的表观总肠道消化率（ATTD）和 STTD。在 P-DE 日粮中，350、600 和 1000 phytase units（FYT）/kg 的 STTD P 释放估计值分别为 0.07%、0.09%和 0.09%，而在 P-AD 日粮中，STTD P 释放估计值分别为 0.02%、0.03%和 0.05%。在 P-DE 日粮中，植酸酶提高了 P 的吸收和保留，并增加了 P 的尿排泄（二次 P<0.001）。在 P-AD 日粮中，植酸酶提高了 P 的吸收（线性 P=0.066），有提高保留的趋势（线性 P=0.066），并增加了 P 的尿排泄（二次 P=0.021）。植酸酶提高了 P-DE 日粮中 P 的 ATTD（二次 P=0.002），但在 P-AD 日粮中没有提高（P>0.1）。总之，在 P 充足的日粮中，植酸酶释放的 P 低于低磷（P）日粮。植酸酶仅在 P 缺乏的日粮中增加 Ca 的利用率。最后，植酸酶提高了 DM 的 ATTD，并且有提高能量 ATTD 的趋势，而与日粮 P 状态无关。
