The differences between Tier 1 and Tier 2 methods are related to the emission factors and the level of livestock disaggregation. Tier 1 is based on the use of IPCC default values while Tier 2 is applied to more disaggregated livestock population categories and uses calculated country-specific emission factors requiring detailed data on energy feed intake, and CH₄ conversion rates for each specific feed type.

When applying a Tier 1 method, data on livestock categories, management, and feeding practices (regional characteristics) and milk production (for dairy cows) should be used to select the appropriate default emission factor. You should check whether the animal characteristics used by a Party (e.g., weight, growth rate, milk production, feeding situation, feed quality, activity) are similar to the conditions considered to derive the default factors.

When applying a Tier 2 method, country-specific emission factors for each animal species and category must be developed. Parties should use the data from their enhanced livestock characterization to develop their emission factors. The IPCC Good Practice Guidance provides information on developing emission factors (energy feed intake and methane conversion rate) for cattle, buffalo, and sheep.