4.2. P excretion
The average faecal P content was 8.9 g per kg of DM (Table 3), close to the value of
8.6 g per kg DM obtained by Wu et al. (2000) when feeding a diet with 4.0 g P per kg
DM in the same lactation period as in our study. Spiekers et al. (1993) divided P excreted
in the faeces of dairy cows into three fractions: (a) the truly indigestible fraction; (b) the
fraction that must be excreted due to the prevailing nutritional and physiological conditions
in the animal; (c) the digestible dietary P which is in excess of the animals needs. Feeding
dairy cows two different low levels of dietary P (2.2 and 2.0 g P per kg dietary DM) they
calculated the fraction b, referred to as inevitable loss, to be 1.2 g P per kg DM intake.