EFFECT ON COW PERFORMANCE AND MILK-FAT COMPOSITION OF INCLUDING FULL FAT SOYBEANS AND RAPESEEDS IN THE CONCENTRATE MIXTURE FOR LACTATING DAIRY-COWS

Two experiments were carried out to determine the effect on milk yield, milk composition and composition and physical properties of milk fat of giving full fat soyabeans (FFS) and full fat rapeseeds (FFR) to dairy cows. In both experiments grass silage was provided ad lib. and constituted over 50% of the dry matter (DM) intake of the cows. In experiment 1, cows received 7.25 kg/d of a concentrate mixture containing 240 g/kg of extruded FFS or 7.25 kg/d of a mixture without soyabeans. Cow performance was not significantly affected by the inclusion of FFS but fatty acid composition of the milk fat was greatly altered. The contents of C8:0 to C16:0 were significantly reduced (P < 0.001) while the contents ofC18:0, C18:l and C18:2 were significantly increased (P < 0.001). Milk fat produced during feeding on FFS concentrate had a significantly lower content of solid fat at temperatures between 0 and 25 °C compared with milk fat produced when FFS was not given. In experiment 2, cows received concentrate mixtures containing either no whole rapeseed, 150 g~kg of whole unground FFR or 150 g/kg of ground FFR. Milk yield was significantly higher and silage DM intake significantly lower with the ground FFR concentrate compared with the other two diets but milk composition was not significantly different among treatments. FFR inclusion, either ground or unground, reduced diet digestibility. Changes in fatty acid composition of the milk fat were similar to those observed with FFS inclusion but the effect was larger with ground FFR compared with unground FFR. Nuclear magnetic resonance analysis showed a lower solid fat content when the FFR diets were employed with the effect being greatest with ground FFR. © 1990, Proprietors of Journal of Dairy Research. All rights reserved.