Response to Climate Change: Evaluation of Methane Emissions in Northern Australian Beef Cattle on a High Quality Diet Supplemented with Using Open-Circuit Respiration Chambers and GreenFeed Emission Monitoring Systems.

The main objective of this study was to compare the effect of supplementing beef cattle with cv. JCU2, cv. JCU4, cv. JCU7 and lucerne on in vivo methane (CH) emissions measured by open-circuit respiration chambers (OC) or the GreenFeed emission monitoring (GEM) system. Experiment 1 employed OC and utilized sixteen yearling Brangus steers fed a basal diet of () hay in four treatments-the three cultivars and lucerne () at 30% dry matter intake (DMI). Polyethylene glycol (PEG) was added to the diets to neutralize tannin binding and explore the effect on CH emissions. Experiment 2 employed GEM and utilized forty-eight animals allocated to four treatments including a basal diet of hay plus the three cultivars in equal proportions at 0%, 15%, 30% and 45% DMI. Lucerne was added to equilibrate crude protein content in all treatments. Experiment 1 showed no difference in CH emissions between the cultivars, between and lucerne or between and the basal diet. Experiment 2 showed an increase in CH emissions in the three levels containing . It is concluded that on high-quality diets, does not reduce CH emissions.