5. Conclusion
Under normal feeding conditions for dairy cows, there seems to be no need to use different absorption coefficients for different concentrate ingredients. Data from the present trial
shows that ADP in concentrate/silage diets is approximately 0.50 when feeding 4.0 g P per
kg DM, and as the true digestibility is higher, a TAC of 0.64 and 0.70 for forages and concentrates respectively, as recommended in NRC (2001), seems reasonable. Therefore, using a
TAC of 0.50–0.55, as still are used in some European countries, might be an underestimation.