Effect of dietary fat source and concentration on rumen microbiome and enteric methane in dairy cows

Dietary fat can reduce enteric methane from dairy cows; but dose response studies are needed for optimization of fat feeding in relation to methane emission. In this experiment, fat concentrations between 3 and 7% were tested, using either cracked rapeseed or palm kernel fatty acids as fat source. Twenty four multiparous cows were used in 6 x 6 Latin square design, with 6 periods of 21 days each. Six treatments were used: a control, 3 fat concentrations (low, medium and high) of rapeseed (RS), and 2 fat concentrations (low and medium) of palm kernel fatty acids (PK). Increased fat supplementation decreased CH4 yield (g CH4/kg of DMI) linearly when RS was used, and quadratically when PK was used. Medium PK concentration reduced CH4 yield more than medium RS concentration, but there was no difference for CH4 intensity (g CH4/kg of ECM).