Current models that predict food intake over time assume that the animal is always fully adapted to the food that it is on. This approach does not account for the immediate effects of a change in food type upon intake. Such a change may have large effects on intake and performance particularly when the change is to a food of higher bulk content. Such a change initially causes a reduction in intake. Over time, with adaptation, intake gradually increases until a new equilibrium intake is reached. The ability to predict intake and performance during the period of adaptation will allow models to predict food intake on high bulk foods more accurately. Data recorded during the period of adaptation are frequently excluded, perhaps to make the prediction of intake on high bulk foods easier. This work is an attempt to develop a model to predict intake and performance during the adaptation period when an animal is changed to a food of higher bulk content.