Effect of nitrate supplementation on diurnal emission of enteric methane and nitrous oxide

Abstract

: The objective of this study was to investigate the effect of nitrate supplementation on diurnal enteric methane (CH 4 ) and nitrous oxide (N 2 O) emissions in dairy cows. Four Danish Holstein dairy cows fitted with ruminal cannulas were used in a 2 × 2 crossover design with 2 periods of 14 d duration. Cows were fed ad libitum with 2 experimental diets based on either urea or nitrate (8.6 g NO kg of DM 3 − / ) supplementation. Samples of ruminal fluid, blood, and rumen headspace gas samples were collected. Gas exchange was measured in respiration chambers during a 96-h period. N 2 O emission was calculated from the ratio between CH 4 and N 2 O in the rumen head space and the measured CH 4 emission. Nitrate supplementation resulted in a lower daily CH 4 production (g/d), CH 4 yield (g/kg of DMI), a lower CH 4 per kg of FPCM, a tendency of lower CH 4 intensity (g/kg ECM), and higher daily