The Estimation of Pasture Intake by the Grazing Sheep

The few estimates in the literature of the quantity of food eaten by the grazing sheep have involved calculations based on some component of the faeces. ’ The “apparent digestibility” of this component was first calculated with sheep fed on known amounts of cut pasture. Faeces were then collected from grazing sheep and the amount of the particular component in the faeces was used to predict the intake. As Lancaster (1949) has pointed out, this technique involves two assumptions : (1) the material used in the pen experiments is similar to that selected by the sheep, and (2) the grazing animal digests the pasture material to the same extent as it does in the pens. As the first assumption is, from observation, almost certainly incorrect, the validity of the second must also be questioned.