Estimating enteric methane production for beef cattle using empirical prediction models compared with IPCC Tier 2 methodology

The Intergovernmental Panel on Climate Change, Tier 2 methodology and 16 empirical models together with dietary information were used to estimate daily methane (CH4) production and Y m (CH4 energy expressed as a percentage of gross energy intake) for mature cows (lactating and dry) and growing steers (backgrounding, grazing, and finishing) in eastern and western Canada. Monthly simulations accounted for changes in body weight, feed intake, and diet composition. Coefficient of variation (CV) and uncertainty (95% confidence interval divided by mean) were used to estimate variability. Estimates of CH4 (g d−1) and Y m from models differed from IPCC estimates. For models, the CV of Y m ranged from 0.8% to 29.7% and uncertainty from 0.9% to 45.2% over the production phases of the animals in contrast to the fixed Y m used by IPCC. When information on diet composition is lacking, a Y m value of 7.0%–7.3% can be used for beef cows depending on stage and location, and 6.4%–6.6% for growing cattle fed high-forage diets, whereas 4.8% is recommended for finishing diets instead of the default values of 6.5% for high-forage diets and 3.0% for finishing diets typically used in the IPCC Tier 2 method.