Cows were milked twice a day, milk yield in each milking was recorded
and daily composite samples were prepared based upon a proportion of morning (AM)
and evening (PM) yields. Composite samples were prepared in two parts for analyses.
One part was refrigerated at 4°C and analysed for milk basic constituents (Milkoscan
apparatus). Separate aliquots were stored at -20°C, freeze-dried, and analysed for fatty
acids [Cieślak et al. 2009] using a gas chromatograph (Varian Star CP 3800) fitted
with flame ionization detector and a 100-m fused silica capillary column (i.d. 0,25)
coated with 0.2 µm of CP-Sil 88 (CHROMPACK, Varian)