The alkane-based and sward sampling techniques were used to estimate pasture intake and diet digestibility. Estimates of pasture substitution, based on measurements made with the alkane technique, were 0.3 and 0.6 kg DM reduction in pasture/kg DM grain consumed at the low and high pasture allowance, respectively, in both years. In year 1, the pasture substitution measured with the pasture difference method was 1 kg pasture DM/kg grain DM at both pasture allowances. In year 2, estimates of substitution calculated using the pasture difference method were 0.2 and 0.5 kg pasture DM/kg grain DM at the low and high pasture allowance respectively.

In the second experiment (year 3), the effects of level of feeding barley on pasture intake, diet digestibility and milk production were measured during summer. The 4 levels of grain consumed were 0, 1.8, 3.4 and 6.7 kg barley DM/cow. day. Higher grain intake resulted in higher milk yield, higher protein concentration and yields of fat, protein and lactose. Milk yield responses per kilogram of barley diminished from 1.6 at the low barley intake to 0.8 kg milk/kg barley DM at the highest barley intake. It is suggested that higher levels of substitution and a potentially less efficient use of grain contributed to the poorer production responses at higher levels of grain feeding.