So how much of our beef actually comes from foreign sources? Researchers with USDA’s Economic Research Service explored that question in the recent report titled “U.S. red meat production from foreign-born animals,” published in the journal Agricultural Sciences.

The researchers note that it is relatively easy to track the amount of meat imported into the United States and the number of imported live animals. Estimating the actual amount of meat produced in the United States from imported animals, however, is more difficult.

The researchers used official U.S. trade data to quantify livestock imported at various weights and stages of production to project the final production dates and weights as a means of estimating the proportion of total U.S. meat supplies produced from imported animals.

The United States typically imports about 2 million head of cattle per year, primarily from Mexico and Canada, representing a wide range of ages and weights, from lightweight stocker calves to finished cattle shipped directly to feedyards. By knowing animal weights at importation, average daily gain at each stage of growth and weights at slaughter, the researchers calculate the time animals would spend in the United States before slaughter and the total quantity of beef produced in any month from imported animals. They then subtract those estimated contributions from the total and combine them with those for imported meat to determine the share of meat consumption in the United States that is due to foreign livestock.

The report shows wide fluctuations in the number of imported cattle during the decade from 2000 through 2010. In 2002, we imported 1.7 million head from Canada, but in 2003, imports from Canada dropped to 513,000 as BSE emerged, and in 2004, imports from Canada were virtually zero. Imports from Mexico made up some of the difference, with 1,370 head imported in 2004, but that was the lowest year of the decade for cattle imports.

On average, according to the report, foreign-born cattle account for 8.1 percent of monthly production. There is seasonal variation, with most beef production from foreign-born animals taking place in the first quarter because of the large numbers of feeder cattle imported and placed on feed in the fall.

The highest proportion of U.S. beef production from foreign sources during the report’s timeline was 13.6 percent in February 2006, while the lowest was 2.9 percent in June 2003.

Over the last decade, imports of meat into the United States and meat produced in the United States from foreign livestock have accounted for roughly 18 percent of total U.S. beef supplies.