Methane emission from grazing sheep and cattle
M.J. Ulyatt, K.R. Lassey , R.J. Martin, C.F. Walker and I.D.
Shelton
AgResearch, Grasslands Research Centre, Private Bag 11008,
Palmerston North
Proceedings of the New Zealand Society of Animal Production. 1997,
57: 130-133
Measurements of methane emissions from individual sheep and
dairy cows grazing typical New Zealand perennial ryegrass/white clover
dominant pastures are reported. These are the first measurements
reported from grazing sheep, and among the first from grazing cattle.
The measurement technique, using a marker gas (sulphur hexafluoride),
enables emission rates to be determined from analyses of "breath"
samples collected while grazing. More than 250 measurements of daily
methane emission from 50 sheep (8 months old) were made, with flock-mean
emission 18.9±0.8 g/d. Emissions were weakly correlated with feed
intake, and they represented a 4.6±0.1% average loss of gross dietary
energy. The corresponding mean emission based on 40 measurements of
daily emissions from 10 lactating dairy cows was 263±10 g/d,
approximately 6.2% of estimated gross energy intake. A notable feature
was the large inter-sheep variability in daily methane emission (range
140%) that could not be attributed to variable intake. This would appear
to suggest an appreciable diversity of methanogenic response to
digestion, and may be significant in the search for strategies to
control emissions of this greenhouse gas.
Keywords: NZSAPAB;
methane emission; sheep; cattle; pasture.
Last Updated 12-09-1998
