To begin with, in regards to accounting for enteric emissions (“cow burps”), most people use global stats. So even if you use 2006 Long Shadow as a reference, and actually read that document, a large portion of that 18% was attributed to land use change specifically in Brazil at peak deforestation rates from 1998 to 2004. If I recall correctly 57% of the GHG’s attributed to cattle was from South America. This report was also just for OECD countries. 2013 Long Shadow scaled the number back some to 14.5% still using 2004-2005 Amazon deforestation rates. Again a global number that still used different Life Cycle Analysis [LCA] methods for different sectors.
More recently the authors of the UN FAO Long Shadow Report, Anne Mottet and Henning Steinfeld, also posted wrote this 2017 article, Cars or livestock: which contribute more to climate change? This article noted that that they used different methodologies for doing Life Cycle Analysis for different sectors (something Dr. Frank Mitloehner pointed this out way back in 2010 about the 2006 report). One way was inclusive of all emissions from the Ag sector, including land use change, and the other was just tail pipe emissions from the transportation sector as shown in the high lit portion of the graphic below. (For full article)