Abstract:
In Australia, livestock are presently responsible for 14% of national greenhouse gas emissions (Australian Greenhouse Office 2001). The national inventory reports that since 1991 methane gas emissions from Australia�s beef cattle population have increased by 4.2 % (Australian Greenhouse Office 2001). The US Environmental Protection Agency (1999) promotes the use of hormonal growth promotants as a tool for greenhouse mitigation in beef cattle, because they reduce the time required to reach market weight by enhancing growth rate, feed efficiency and lean tissue accretion. The objective of this study was to quantify the reduction in methane gas output from beef cattle repeatedly treated with oestradiol under experimental field conditions in tropical Australia.