Primary Audience: Animal Nutritionists SUMMARY

Due to the increase in the prices for feed phosphates, acceptance of the finiteness of the global phosphate stores and environmental concerns associated with excessive excretion of phosphorus, i.e., P, by livestock, the knowledge about the availability of P from different P sources has gained in importance in the last decade. The development of a standardized method for P evaluation has been the first step for optimizing the dietary P concentration in poultry diets. The determination of exact quantitative values of the P availability in different plant and mineral P sources will make it possible to formulate diets which are closer in their available P content to the needs of a bird while minimizing or avoiding excess supplementation. Because many studies were published that were based on bone data and relative bioavailability calculations, we investigated whether relative bioavailability data obtained with bones can be recalculated and merged with the quantitative data into one P availability table. It was concluded from this comparison that it was not possible to combine data from quantitative and relative P availability measurements into one P availability table