The principal reasons for measuring herbage intake are (1) to understand the relationships between sward attributes such as structure or composition and herbage intake, and (2) to explain differences in animal performance associated with different grazing systems or management strategies. These two objectives may require the use of different techniques, as will be outlined below, but all techniques require to meet the criteria of having a precision suitable for the purpose of the measurement, producing minimal disturbance to grazing acitivity, giving unbiased results and being as undemanding of labour and thus as inexpensive as possible. Animal-based estimates have the advantage over other methods in that they allow an examination of between-animal variation.