Department of Animal Sciences, University of Illinois, Urbana.
Institute of Animal Science, University of the Philippines, Los Baños, Philippines.
J Anim Sci. 2019 Feb 1;97(2):756-767. doi: 10.1093/jas/sky439.
An experiment was conducted to test the hypothesis that pigs fed diets supplemented with exogenous phytase reduce mucin synthesis in the small intestine, increase protein hydrolysis in the stomach, increase breakdown of phytate along the gastrointestinal tract, and increase mineral and AA digestibility. A diet based on corn, soybean meal, and canola meal was formulated to meet requirements for growing pigs except for Ca and P, which were lower than requirements. Three additional diets were formulated by adding 750, 1,500, or 3,000 units of phytase (FTU) per kilogram to the basal diet. Eight growing barrows (38.45 ± 3.06 kg) were prepared with a T-cannula in the duodenum and another T-cannula in the distal ileum. Pigs were housed individually and allotted to a replicated 4 × 4 Latin square design with four pigs and four periods in each square. Each period lasted 14 d with the initial 7 d being the adaptation period to the diets. Pigs were fed twice daily in combined amounts equal to 3.2 times the estimated requirement for maintenance energy. Results indicated that the apparent ileal digestibility (AID) and the apparent total tract digestibility (ATTD) of Ca and P increased (linear and quadratic, P ≤ 0.05) as phytase inclusion increased. However, values for AID of Ca and P were not different from values for ATTD of Ca and P, indicating that there is no net absorption of Ca and P in the hindgut. The apparent duodenal digestibility (ADD) of Ca and P was ~30% and 10% to 20%, respectively, indicating some digestion in the stomach of both Ca and P. A quadratic increase (P < 0.05) of the AID of GE was observed with the breakpoint around 1,500 FTU, but there was a negative linear (P ≤ 0.001) effect of dietary phytase on the ATTD of GE. Phytase did not affect mucin synthesis in the small intestine, protein hydrolysis in the stomach, or ileal digestibility of dispensable and indispensable AA. However, degradation of higher phytate esters (IP6 and IP5) into lower phytate esters (IP4 and IP3) and inositol increased as dietary phytase increased, indicating that it is possible to completely degrade dietary phytate if microbial phytase is included by at least 3,000 FTU in the diet. In conclusion, supplementing diets with phytase resulted in increased degradation of phytate and phytate esters and improved digestibility of Ca and P, but phytase did not change intestinal mucin synthesis, gastric protein hydrolysis, or the AID of AA.
添加外源植酸酶的日粮可减少小猪小肠内粘蛋白的合成，增加胃中的蛋白质水解，增加胃肠道中植酸的分解，并提高矿物质和 AA 的消化率。设计了一种以玉米、豆粕和菜粕为基础的日粮，以满足生长猪的要求，但钙和磷低于要求。通过在基础日粮中添加 750、1500 或 3000 个植酸酶单位（FTU），另外配制了 3 种日粮。8 头生长肥育猪（38.45±3.06kg）在十二指肠和回肠远端分别安装 T 型管。猪单独饲养，采用 4×4 拉丁方设计，每个方有 4 头猪和 4 个周期。每个周期持续 14 天，前 7 天是适应日粮的阶段。猪每日分两次饲喂，总量相当于维持能量估计需要量的 3.2 倍。结果表明，随着植酸酶添加量的增加，钙和磷的回肠表观消化率（AID）和总肠道表观消化率（ATTD）呈线性和二次增加（P≤0.05）。然而，钙和磷的 AID 值与钙和磷的 ATTD 值没有差异，表明在后肠中没有钙和磷的净吸收。钙和磷的十二指肠表观消化率（ADD）分别约为 30%和 10%~20%，表明胃对钙和磷都有一定的消化作用。GE 的 AID 呈二次增加（P<0.05），转折点约为 1500FTU，但日粮植酸酶对 GE 的 ATTD 呈负线性（P≤0.001）影响。植酸酶对小肠粘蛋白合成、胃蛋白水解或可利用和必需 AA 的回肠消化率没有影响。然而，随着日粮植酸酶的增加，较高植酸酯（IP6 和 IP5）降解为较低植酸酯（IP4 和 IP3）和肌醇的量增加，表明如果日粮中至少添加 3000FTU 的微生物植酸酶，日粮中的植酸是可以完全降解的。总之，日粮中添加植酸酶可增加植酸和植酸酯的降解，提高钙和磷的消化率，但植酸酶不会改变肠道粘蛋白合成、胃蛋白水解或 AA 的 AID。
