Effect of a biosynthetic bacterial 6-phytase on the digestibility of phosphorus and phytate in midlactating dairy cows

By: Yueming Dersjant-Li, Ivonne Kok, Edwin Westreicher-Kristen, Rubén García-González, Alessandro Mereu, Trine Christensen, Leon Marchal

Traditionally, it has been believed that dairy cows are able to fully utilize the phosphorus (P) in feed, including that from plant-derived phytate, because of phytase activity of bacteria in the rumen. However, recent data have shown otherwise. This study investigated the effect of a biosynthetic bacterial 6-phytase supplemented to the diets of midlactating dairy cows on the digestibility and excretion of phosphorus and other key nutrients, over a 19-d experimental period. The experimental diets were commercially relevant in composition and low in phosphorus. At either or both of two tested dose levels (2,000 and 5,000 phytase units (FTU) per kilogram DM in the total diet), the exogenous phytase increased the digestibility and reduced fecal excretion of crude protein (CP), total P, and phytate-P compared with a comparable unsupplemented diet. The increases in CP, PP, and P digestibility were phytase-dose dependent. In addition, at the highest dose level, the phytase tended to increase the protein content of milk. The findings indicate that the use of exogenous phytase can improve P and protein utilization in dairy cows and offers an important approach to optimizing nutrient balance and reducing environmental P and nitrogen (N) pollution from dairy farms.