Interest in the use of whole crop cereals as a complementary forage for dairy cows has developed in Europe over the last fifteen years. Initial studies in the UK concluded that near maximum dry matter (DM) yield/ha of whole crop wheat (WCW) occurred in late July/early August when crops contained at least 500 g/kg DM. However, it was noted that when these crops were ensiled they tended to be aerobically unstable. To minimise this problem it was recommended that these crops were preserved with urea rather than being ensiled. Early studies with dairy cows demonstrated that the use of both urea-treated and low DM fermented WCW increased forage intake and milk yield but effects on milk composition were inconsistent (Leaver and Hill, 1992, Phipps et al., 1995). Concern has been expressed that the use of urea in crop preservation was environmentally unacceptable and that high DM fermented WCW offered a possible alternative, which would provide high DM yields/ha of a starch-rich crop. The objective of the current study was to examine the effect of crop maturity on feed intake and milk production of dairy cows. An additional treatment was included to examine the effectiveness of an additive containing L. buchneri designed to improve aerobic stability.