Danisco Animal Nutrition and Health, IFF, Oegstgeest, The Netherlands.
Schothorst Feed Research (SFR), Ruminants Group, Lelystad, The Netherlands.
J Anim Sci. 2023 Jan 3;101. doi: 10.1093/jas/skad032.
The effect of a biosynthetic bacterial 6-phytase (PhyG) on the digestibility and excretion of crude protein (CP), phosphorus (P), and phytate-P (PP) in midlactating dairy cows was investigated. Thirty Holstein-Friesians were assigned to three treatments with 10 cows per treatment in a randomized block design. Cows were fed forage (grass and corn silage) provided ad libitum, and a concentrate (without added inorganic phosphate) administered separately in amounts individualized per cow according to milk production, supplemented with phytase according to treatment. The formulated forage-to-concentrate-ratio was ~65%:35%. Dietary treatments comprised the control diet (CON) and CON supplemented with 2,000 (PhyG2,000) or 5,000 (PhyG5,000) phytase units (FTU)/kg DM in the total diet. The experiment comprised an 18-d preperiod for the collection of data to facilitate the allocation of cows to the treatments, followed by a 19-d experimental period comprising a 14-d diet adaptation period and 5 d of twice daily feces collection. Fecal samples were analyzed for the determination of apparent total tract digestibility (ATTD) of chemical constituents in the diet. The ATTD of PP was 92.6% in CON suggesting a high but incomplete degradation of phytate by ruminal microbial phytases. Cows fed PhyG2,000 exhibited increased ATTD of CP and PP [68.4% (2.7% points above CON) and 95.1% (2.5% points above CON), respectively] whilst PhyG5,000 further increased ATTD PP and also increased ATTD P [54.1% (7.8% points above CON)]; ATTD of Ca tended to be increased in PhyG5,000 vs. CON. Linear dose-response relationships were observed for ATTD of DM, CP, P, Ca, and PP. In addition, fecal excretion of P, and PP linearly reduced and that of Ca and CP tended to linearly reduce with increasing PhyG dose level. No difference was observed for DM intake and milk composition was unaffected except for milk protein which tended to be higher in cows fed PhyG5,000 than CON. In summary, the addition of exogenous phytase at 2,000 FTU/kg or higher to diets of lactating dairy cows improved P, PP, Ca, and CP digestibility and reduced fecal excretion of P, PP, and CP in a dose-dependent manner.
研究了一种合成细菌 6-植酸酶（PhyG）对泌乳中期奶牛粗蛋白（CP）、磷（P）和植酸磷（PP）消化率和排泄率的影响。将 30 头荷斯坦-弗里生奶牛按随机区组设计分为 3 组，每组 10 头。奶牛自由采食饲草（草和玉米青贮），并根据产奶量单独给与浓缩饲料（不添加无机磷），并根据处理添加植酸酶。制定的饲草-浓缩料比例约为 65%：35%。日粮处理包括对照日粮（CON）和补充 2000 （PhyG2000）或 5000 （PhyG5000）植酸酶单位（FTU）/kg DM 的日粮。实验包括 18d 的预试验期，用于收集数据以方便将奶牛分配到处理组，然后进行 19d 的试验期，包括 14d 的日粮适应期和 5d 的每日两次粪便收集期。粪便样品用于测定日粮中化学物质的总肠道表观消化率（ATTD）。CON 组 PP 的 ATTD 为 92.6%，表明瘤胃微生物植酸酶对植酸的降解程度较高，但不完全。饲喂 PhyG2000 的奶牛 CP 和 PP 的 ATTD 增加[68.4%（比 CON 高 2.7%）和 95.1%（比 CON 高 2.5%）]，而 PhyG5000 进一步增加了 PP 的 ATTD，同时也增加了 P 的 ATTD[54.1%（比 CON 高 7.8%）]；PhyG5000 组的钙 ATTD 呈增加趋势。DM、CP、P、Ca 和 PP 的 ATTD 呈线性剂量反应关系。此外，随着植酸酶添加量的增加，P 和 PP 的粪便排泄量呈线性减少，Ca 和 CP 的粪便排泄量呈线性减少。DM 摄入量没有差异，除了牛奶蛋白外，牛奶成分不受影响，饲喂 PhyG5000 的奶牛的牛奶蛋白含量略高于 CON 组。总之，向泌乳奶牛日粮中添加 2000FTU/kg 或更高水平的外源植酸酶可提高 P、PP、Ca 和 CP 的消化率，并以剂量依赖的方式减少 P、PP 和 CP 的粪便排泄量。
