A randomised complete block design was used to study the effects on animal performance of (1) the increasing level of supplementary concentrate with grass silage (GS), and (2) feeding GS and concentrates separately or as a total mixed ration (TMR). A feeding experiment comprised 32 dairy bulls with average initial live weight of 145 kg. The feeding treatments were: (1) GS (660 g kg-1 dry matter intake) plus medium level of rolled barley (330) offered separately, (2) GS (660) plus medium level of rolled barley (330) offered as TMR, (3) GS (330) plus high level of rolled barley (660) offered separately, and (4) GS (330) plus high level of rolled barley (660) offered as TMR. During the experiment (398 days) the bulls were fed ad libitum either GS or TMR. The increasing concentrate level increased energy intake, carcass gain and dressing proportion of the bulls but had no effects on carcass conformation or fat score. TMR feeding had no effects on carcass gain, dressing proportion, carcass conformation or fat score but increased dry matter and energy intake compared to the separate feeding.