In most dairy production systems, grazed herbage is potentially the cheapest forage resource. However, while the availability is affected by seasonal changes in herbage growth, and/or between year variations in climatic conditions, the requirements of dairy production systems tend to remain constant throughout the season. This paper summarises five experiments that examined the effect of the characteristics of the forage supplement (dry matter, DM; metabolisable energy, ME, content; Type) and the effect of stage of lactation and access method to the supplement on animal performance