Canada's agricultural emissions accounted for 60 Mt or 8% of national greenhouse gas (GHG) emissions in 2007. The estimation of CH4 emission factor (B0) from manure management systems in Canada is prone to uncertainty owing to lack of B0 values for Canadian conditions. Therefore, in this study, manure samples from six Canadian animal farms, two each of swine, beef and dairy cattle, were investigated in order to estimate their methane production potential (B0). The ultimate anaerobic biodegradability was measured with ISO standard batch fermentation. The extent of biodegradation of the manure samples with or without sodium benzoate was always greater than 60% and hence showed no inhibitory effect on methane production by the manure. The impact of use of antibiotics in the animal feed on methane production was also considered; however, no inhibitory effect on methane production could be observed. The plateau of methane production in all cases was achieved by 63 d of anaerobic digestion process and the final pH was within 6-8. The calculated B0 were in the range of 0.47-0.42, 0.21-0.19 and 0.35-0.30 for swine, beef cattle and dairy cattle, respectively. The uncertainties associated with B0 values were +/- 9% for swine, +/- 3% for beef cattle and, +/- 6 and +/- 2% for dairy cows.