The accurate prediction of the food intake of cows is a necessary step in the formulation of dairy rations because the formulation to meet requirements will depend on the level of intake. Intake may change as lactation progresses. The way in which intake changes with stage of lactation on foods of different composition is therefore central to intake prediction systems. However, in the vast majority of existing experiments, the influence of stage of lactation on intake is confounded with changes in either the allocation of the ration or the composition of the diet. The results reported here are from the first part of an experiment which was carried out to provide, for the first time, intake data for dairy cows throughout lactation where diet composition remains constant.