I believe this is a very US-centric viewpoint.
I'm using the article 'Beef Cattle and Greenhouse Gas Production' from Ministry of Agriculture, Food and Rural Affairs.
http://www.omafra.gov.on.ca/english/livestock/beef/news/info...
According Food and Agricultural Organization (FAO) of the UN 2006 report livestock were responsible for 18% of all human-related greenhouse gas production. 14.5% according to 2013 report.
Of that 43% is Enteric.
There may only be 9% GHG emissions in the US, but beef also comes from other countries where these emissions are very different. See Regional and Production System differences.
From the article -- There was an approximately 4-fold difference in emission intensity between the top 10% of producers and the bottom 10% of producers within a system.