DIM did not affect DM intake (DMI). Increased DIM decreased milk yield, both measured as kg milk and kg energy corrected milk (ECM). Fat supplementation increased milk yield compared to CON, however ECM yield was not affected. Milk protein concentration decreased with fat supplementation. Methane produc- tion increased with DIM when measured in L/d, L/kg DMI and L/kg ECM. However, when CH4 production was expressed as L/kg ECM there was a tendency for interaction between DIM and treatment