Proxies to adjust methane production rate of beef cattle when the quantity of feed consumed is unknown.

The aim of this experiment was to evaluate the utility of CO2 production rate (CPR; g CO2/d) and animal weight (WT) data as proxies for feed-intake to adjust methane production rate (MPR; g CH4/d) in situations where dry-matter intake (DMI) is not known. This experiment measured individual-animal DMI, MPR and CPR in the feedlot, and then again on restricted quantities of grain and roughage diets in open-circuit respiration chambers. Of the 59 cattle tested in the feedlot, 41 had MPR and CPR recorded, and 59 and 57 had test results on the restricted grain and roughage rations.