Effects of partial replacement of grass silage with maize silage on feed intake, enteric methane emissions and milk production in dairy cows in northern conditions

We conducted three experiments to investigate the effects of partial replacement of grass silage with maize silage (25% or 50% of the dry matter [DM]) on feed intake, milk production, diet digestibility, and methane (CH4) emissions in dairy cows. The starch concentrations of maize silages were high for northern latitudes and ranged from 236 g kg-1 DM at early harvest to 278 and 254 g kg-1 DM at late harvest, respectively. Partial replacement of grass silage with maize silage increased feed intake, whereas diet digestibility decreased. Milk and energy corrected milk (ECM) yields increased in one experiment, whereas no corresponding changes were observed in the other experiments. Replacing grass silage with maize silage improved nitrogen utilization in all the experiments and CH4 intensity (g kg-1 ECM) decreased in one experiment. In northern conditions, the beneficial effects of maize silage on feed intake can be achieved, while effects on milk production and enteric CH4 emissions are less consistent due to annual variation in maturity and starch content of maize.