Thirty six lactating cows were used in a trial with a partially balanced change-over design to determine the effect of the fineness of roughage and concentrate to roughage ratio on intake and digestibility. Nine rations were used with combinations of 3 screen sizes (6, 13, 19 mm) and 3 concentrate percentages (35, 50, 65). Maize straw was included as a poor quality roughage component. An increase in the concentrate component and a decrease in screen size resulted in an increased intake of 44 per cent. Each combination of screen size and concentrate to roughage ratio resulted in a different intake. It was found that the fineness of a ration becomes less important at high concentrate levels. Intake increased with increasing concentrates in the diet which indicated that at the 65 per cent concentrate level the possible point of constant DE-intake was not obtained with maize straw as roughage component. Digestibility studies at ad libitum intake indicated that screen size and concentrate to roughage ratio had no effect on apparent DM and N digestibilities. Apparent fibre digestibility was significantly (p< 0,01) decreased by 0,3 per cent and 0,5 per cent with 1 per cent increase in concentrate and one mm decrease in screen size, respectively.