Feeding phosphorus (P) to cattle: A new basis for Nordic recommendations

Phosphorus (P) is an essential nutrient and significant safety margins have until now been included in both feeding recommendations for cattle and allocation of P in practice. However, there is a need to optimize the utilization of P in cattle and thereby minimize its allocation and excretion. This demands well-defined requirements and availabilities of P in feeds as well as fairly precise use of this knowledge in practice. The purpose of this paper is to review the current knowledge and to give proposals for feeding phosphorus to cattle in relation to physiological requirement, availability of phosphorus in feeds, and minimal excretion of P. There is scientific and practical basis for a reduction of recommendations and allocation of P to cattle in the Nordic countries. No evidence or indication is found that surplus P relative to physiological requirement is beneficial. Future P feeding recommendations should continuously be based on the factorial method. The quantitatively most important improvement will be the increase and differentiation of the TAC value (true availability coefficient), which can be raised from 0.55 to 0.65 and 0.70 for the most common feeds. However, there is still no basis for a specific TAC for an individual feedstuff. When applying the recommended P allocation, it will be possible to increase the utilization of P in, e.g. high producing dairy cows, to 35–40%.