In a feeding experiment 3 x 12 dairy cows (German Simmental x Red Holstein Friesian) were used to investigate the influence of different amounts of fodder beets on feed intake, milk yield and milk composition. The fodder beets (variety Kyros) were fed in exchange for concentrate. The amounts of fodder beets were either 22 kg cow-1 d-1 or 44 kg cow-1 d-1 or zero (control group). All groups received 4 kg hay cow-1 d-1, grass silage ad libitum, and concentrate corresponding to the milk yield. In order to balance the rations the concentrate was either rich in protein or rich in energy. Feeding 22 kg or 44 kg fodder beets increased forage intake (including fodder beets) significantly. However, the total feed intake diminished on average from 18.3 kg DM cow-1 d-1 (control group) to 17.2 kg DM cow-1 d-1 (fodder beet groups). In each treatment the intake of hay was 3.3 kg DM cow-1 d-1. However, the intake of grass silage offered ad libitum was significantly suppressed by the fodder beets. Considering the different amounts of concentrate the quantity of suppression of grass silage by feeding fodder beets was calculated at -0.8 kg DM of grass silage per kg DM of fodder beet intake. The milk yield decreased linearly with increasing fodder beets on average up to 4 kg cow-1 d-1. However, the milk composition was scarcely influenced. The fat content increased a little, the mean alterations of the protein and lactose content were below 0.1 percentage points. Therefore, the change in daily excretion of milk fat, protein or lactose were similar to the change in milk yield. In conclusion, feeding fodder beets in combination to grass silage causes a positive effect on forage intake (including fodder beets). However, the amount of concentrate should not be reduced equivalently to the energy contents of the added fodder beets.