From The USDA Briefing Room - Part 1

Beef Trade

The United States, although the largest producer of beef in the world, is a net beef importer. Most beef produced and exported from the United States is grain-finished, high-value cuts. Most beef that the United States imports is lower value, grass-fed beef destined for processing, primarily as ground beef.
U.S. beef production hit its cyclical low in 2004, when sharply reduced cow slaughter reduced domestic supplies of processing beef and total beef imports topped 3.6 billion pounds. (See the Background chapter for information on the cattle cycle.) U.S. beef production began growing in 2005 as herd rebuilding started. Herd rebuilding was interrupted in 2006 and has continued to stall through 2008 due to widespread drought conditions and sharply higher feed costs, which resulted in increased cow slaughter. This raised domestic processing beef supplies and crowded out some imports of lean beef. Imports continued to decline through 2007 and 2008.
U.S. beef exports had grown steadily since the early 1980s, reaching 2.5 billion pounds in carcass weight equivalent in 2003. This total represented about 9 percent of U.S. beef production. However, in December 2003, the discovery of BSE in a dairy cow which had been imported from Canada led many importing countries to either ban or restrict beef and cattle imports from the United States. Since then, the United States has reported two more cases of BSE, in cows found in Texas (initially tested in November 2004, then confirmed in June 2005) and Alabama (detected and confirmed in March 2006).