Concentrate and silage samples were collected
daily during the sample collection period. Silage
samples were dried at 105 8C for 24 h. Concentrate
and dried silage samples were ground in a hammer
mill (1 mm screen), pooled by period, and stored in
sealed jars at room temperature until analysis.
Faeces were collected quantitatively during the 5
day sample collection period. Faeces were immediately
removed from the rubber mats into plastic
barrels. Daily faecal production of each cow was
weighed and mixed thoroughly with 5 l of water,
sampled and stored at 18 8C until freeze-dried in a
Heto cd8 freeze-drier with an acrylic chamber (Heto
Lab Equipment A/S, Denmark) at a condenser
temperature of 50 8C for 5 days. Faecal samples
were then handled in a similar manner as feed
samples. It is known that urinary P excretion is only
biologically significant when P intake is higher than
required (Morse et al., 1992). Therefore, urine
sampling took place during the last period, when P
intake was highest in relation to the requirement due
to the decreased milk production. Spot samples of
urine were taken morning and evening during the
collection period (5 days), and a total of 9 urine
samples per cow were collected for P analyses.