The methodology for the enteric emissions footprint is described in Section 2.2.2 of the Thoma (2013) paper. The researchers analyzed a number of estimation methods and landed on one from Ellis (2007).
FARM ES uses DMI to estimate enteric emissions as described in Section 2.5.
The regional and national benchmarks for FARM ES V2 do not include feed production. This is because the feed emissions factors were updated for Version 2, but there was no way to update the benchmarks because the original ones were generated through a national survey of farms.
The regional and national benchmarks are static averages from the LCA research published in 2013. They are not currently dynamic based on data in FARM ES.