In 2004, the U.S. Government asked farmers to use EID or Electronic Identification ear tags on all their cattle. This request was part of the National Animal Identification System (NAIS) spurred by the discovery of the first case of mad cow disease in the United States. Due to poor performance and concern that other people could access their confidential information, only about 30 percent of cattle producers in the United States tried using EID tags using standards based on the low frequency standards, while the UHF standards are being mandated for use in Brazil, Paraguay, and Korea .EID Tags - The Next Generation , CattleIdentification.org The United States Department of Agriculture maintains a list of manufacturers approved to sell ear tags in the USA.
