A number of experiments have examined the milk production responses to feeding concentrates and forages in total mixed rations (TMR) compared with being fed separately. Grass and maize silages have very different energy and protein levels/sources, but the responses to feeding them mixed as opposed to separately has not been examined. This experiment compared grass and maize silages mixed, or fed separately within days or fed on alternate days. Two levels of protein were offered in the concentrate supplement to examine possible interactions between feeding method and protein content of the diet.