peer reviewed ; Influence of milk in diet of growing fattening Belgian Blue bulls on animal performances and on fatty acid composition in subcutaneous, intermuscular and intramuscular fats. The use of milk as component of a fattening diet for bulls was studied in an experiment carried-out over 2 years with Belgian Blue bulls. The animals weighed 305 kg at the beginning of the experiment. In all, 15 bulls were given a control concentrate fattening diet (control group, CG), while 11 others were fed concentrate plus 6.5 to 11 1 whole milk per day according to weight or age (milk group, MG). The fattening period lasted for 174 and 181 d respectively in groups CG and MG. The MG-group had a higher killing-out percentage (P < 0.01) and the meat was characterized by a lower b* value and a lower dry matter content (P < 0.1). Whole milk in the diet increased the proportion of shorter chain and saturated fatty acids in fat (P < 0.001) and reduced the proportion of mono- and polyunsaturated acids (P < 0.05; P < 0.1). The extent of the changes were larger in subcutaneous and intermuscular fats than in intramuscular fat.