Published online by Cambridge University Press: 02 September 2010
In general the energy supply is the main factor limiting the output of milk by the dairy cow from most food sources. Under Northern Ireland conditions grass produces a greater energy output per unit area than any of the other major crops grown there. Furthermore Lowe (1970) has estimated the relative production costs per unit of dry matter for cereals and root crops to be twice and eight times respectively those incurred with grass. Therefore it is apparent that both on a basis of energy output per unit area, and per unit cost input, grass must continue to provide the maximum possible proportion of the food supply for the dairy industry within Northern Ireland.