Phosphorus availability in feed phosphates determined by regression

Due to environmental concern a lot of effort has been dedicated to improve the utilisation of phytate phosphorus (P) in cereals and seeds. Consequently, microbial phytases are added to pig diets at the expense of feed phosphates. However, there is still a need for inclusion of feed phosphate, especially in diets for young piglets and lactating sows in order to meet their P requirement. This creates a demand for feed phosphates with a high P availability. Fourteen feed phosphates, including two newly developed monocalcium phosphates (MCP), were tested in this experiment. For each source, a series of 5 diets was prepared by inclusion of increasing amounts of either MCP or MSP. These diets were offered to pigs kept in metabolism crates (6 pigs on each of the 5 diets). After 5 days adaptation, total collection of faeces and urine was performed for 7 days. P availability in each source was determined by regression of the net absorption of P on P-intake. The experiment revealed that MSP had the highest availability (79%) and the availability of all the tested phosphates varied between 50 and 79%. The new MCPs proved to be 71 and 75% available.