Methane emissions from non-lactating pregnant dairy cows while grazing

There is little information on methane (CH4) emissions from non-lactating pregnant dairy cattle when grazing. To address this issue, enteric CH4 emissions were estimated from a total of 68 non-lactating pregnant Holstein-Friesian dairy cattle during three successive years (23, 22 and 23 cows in year 1, 2 and 3, respectively). Cows used in these studies ranged from 19 to 69 days prior to their actual calving date when measurements commenced. Methane emissions were measured using the sulphur hexafluoride (SF6) technique over six consecutive 24-h periods, with measurements commencing 28 August, 16 September and 15 September during years 1-3, respectively. Cows were given access to fresh grazing on the first and fourth day of the measurement period, but were not offered a concentrate supplement. Across the three years of the experiment mean CH4 emissions were 216 g/cow/day and 25.2 g/kg dry matter intake. Emission increased with increasing lactation number, from 200 (1st lactation) to 228 (> 2nd lactation) g/day. Relationships between individual cow body weight and methane emissions (R2 = 0.17) and estimates of intakes for individual cows and CH4 emissions (R2 = 0.21) were poor.