EFFECTS OF SUPPLEMENTATION WITH HYDROGENATED FISH FAT ON DIGESTION IN DAIRY-COWS

Three dry cows received a diet based on maize silage according to a 3 x 3 Latin square design, without or with a fat supplement composed either of crystalline hydrogenated fish oil (rich in arachidic and behenic acids) or rapeseed oil (rich in unsaturated fatty acids). The fatty acid content of the diets was 1.5, 8.6 and 8.7%. dry matter (DM) respectively. Fish oil supplementation did not decrease fibre digestion and did not modify ruminal fermentation, in contrast to rapeseed oil which altered ruminal fermentation. Digestibilities of lipids and fatty acids were lower when the diet was supplemented with fish oil than when the other 2 diets were fed because of the low digestibility of all fatty acids, whatever the chain length.