The northern beef cattle herd accounts for more than half of Australia’s
beef cattle population, and is a major source of anthropogenic methane
emissions for Australia. National Greenhouse Gas Inventory predictions of
methane output from Australian beef cattle are based on a predictive equation
developed for British breeds of sheep and cattle offered temperate
forage-based diets. However, tropical forage diets offered to cattle in
northern Australia differ markedly from temperate forage-based diets used in
the United Kingdom to develop the predictive equations. In this paper we
review recent respiration chamber measurements of daily methane production for
Brahman cattle offered a tropical forage or high grain diet, and compare them
with values predicted using methodologies of the Australian National
Greenhouse Gas Inventory Committee and the Intergovernmental Panel on Climate
Change. We conclude that a reliable inventory of methane emissions for cattle
in northern Australia can only be achieved after a wider range of tropical
forage species has been investigated. Some opportunities for reducing methane
emissions of beef cattle by dietary manipulation are discussed.