The aim of this study was to evaluate the effects of high levels of whole raw soya beans in the diets of lactating cows. Twelve Holstein dairy cows were used, randomized in three 4 × 4 balanced and contemporary Latin squares and fed the following diets: (i) control (C), without including whole raw soya beans; (ii) 80 g/kg in DM of whole raw soya beans (G80); (iii) 160 g/kg in DM of whole raw soya beans (G160); and (iv) 240 g/kg in DM of whole raw soya beans (G240). There was significant reduction (p < 0.05) in dry matter intake (kg/day) in cows supplemented with G240 compared with C (23.8 vs. 25.3 respectively). G240 diets presented lower crude protein digestibility (g/kg) (p < 0.05) in comparison with C diet (683 vs. 757 respectively). There was significant effect of experimental rations in nitrogen balance (p < 0.05), G240 diet presenting significant reduction in comparison with the other diets, and faecal excretion of nitrogen was higher for G240 diet. The concentration of ruminal ammoniacal nitrogen was significantly higher (p < 0.05) for cows receiving control diet, compared to other diets. G240 diet resulted in significantly lower milk and protein yield (p < 0.05) in comparison with C diet. Significant C18:2 cis fatty acids were observed in milk concentrations (p < 0.05) for G240 diet. The use of high level of whole raw soya beans in dairy cow diets improves the unsaturated fatty acid profile in milk, and the diets (G80 and G160) led to minor alterations in the digestive processes and animal metabolism.