The effect of crushed full fat rapeseed or its free oil on milk yield and milk fatty acid composition was assed
using three groups of mid-lactating Holstein dairy cows, assigned to a randomized 3 3 Latin square design.
Dietary treatments included a control (CTL, ether extract 2.3% of dry matter, DM) and two experimental
treatments (ether extract 4.2% of DM) supplemented with the same amount of fat either supplied as 4.9% of
DM crushed full fat rapeseed, RCor2.2% of DM free rapeseed oil RO. Both experimental treatments increased
DM intake (Po0.005) and daily milk yield (Po0.001). Milk fat and protein concentration was decreased in
the supplemented diets (po0.001). A reduced (po0.001) yield of saturated fatty acids (FA) and an increased
yield of long chain and unsaturated FA (po0.001 for mono unsaturated FA and po0.05 for poly unsaturated
FA) in milk fat was observed for both experimental treatments. The results confirmed a reduced de novo
synthesis and an increased carry-over of dietary FA upon feeding dairy cow diets supplemented with long
chain and unsaturated FA. The lower degree of saturation in milk fat from cows fed RC compared to RO
indicates a partial protection of the crushed rapeseed against ruminal hydrogenation