Optimisation of supplementation of forage with concentrates is essential to improve efficiency and economic sustainability of dairy cow production systems, as well as reducing the environmental impact of intensive dairy farming. However, continuing fertility and health problems indicate that we are not responding effectively to the needs of high genetic merit dairy cows in terms of current feeding and management strategies. A programme was initiated to examine the consequences of nutritional manipulation of dairy cow diets on animal performance in order to attempt to reprogramme the nutrient partitioning of the animal towards maintenance of body reserves rather than excessive milk yield and to potentially alter the lactation curve to give a flatter curve of milk production.