It is the U.S. Department of Agriculture's second attempt at implementing such a system, which officials say is critical to maintaining the security of the nation's food supply. An earlier, voluntary program failed because of widespread opposition among farmers and ranchers who described it as a costly hassle that didn't help control disease.
There has been talk for years among consumer advocates about establishing a program that would trace food from farm to plate. The livestock identification system doesn't go that far and isn't meant to. Its main goal is to track animals' movements so agriculture and health officials can quickly establish quarantines and take other steps to prevent the spread of disease.
"This ensures that healthy animals can continue to move freely to processing facilities, providing a dependable and affordable source for consumers as well as protecting producer's livelihoods," Abby Yigzaw, spokeswoman for the USDA's Animal and Plant Health Inspection Service, said in an email.
Michael Doyle, director of the University of Georgia's Center for Food Safety, said livestock identification also helps investigators determine the source of disease and whether it happened naturally or someone tampered with the food system.
"Identify the farm from which it originated, which can help you identify the source," Doyle said, adding, "Did it come in from the feed? Was it intentional?"
The federal government has been trying for nearly a decade to establish an animal identification system. It introduced a voluntary program in 2006 but scrapped it several years later amid widespread complaints from farmers about the expense and red tape. Some also worried about possible privacy violations with the collection of information about their properties. The program ultimately failed because relatively few participated.
The new program is mandatory but more limited in scope. It applies only to animals being shipped across state lines, and it gives states flexibility in deciding how animals will be identified an important concession to cattle ranchers in western states, where brands are still commonly used.
While the program covers a range of livestock, much of the focus has been on cattle. That's partly because aggressive programs to fight diseases such as sheep scabies have already resulted in widespread identification of those animals, said Neil Hammerschmidt, APHIS' animal disease traceability program manager. Tracking cows has been less of a concern over the past decade because earlier programs targeting diseases that affect them have been successful, he said.
Still, tracebacks in which a sick animal's movements are reviewed as part of the effort to control the spread of a disease aren't unusual. Dr. Paul McGraw, the state veterinarian in Wisconsin, a top dairy state, recalled a number done because of tuberculosis in cattle.
"It's probably safe to say nationwide, there's probably been five or six of those in the last two to three years," McGraw said.
The rules that went into effect March 11 require dairy cows and sexually intact beef cattle over 18 months of age to be registered when they are shipped over state lines and outline acceptable forms of identification. In most cases, farmers and ranchers are likely to use ear tags that assign a number to each animal.
"I'd say it's very similar to a license plate on a car," Hammerschmidt said.
In Wisconsin, many of the larger dairy farms have already switched to ear tags that can be scanned electronically, said Mark Diederichs, president of the Board of Directors of the Professional Dairy Producers of Wisconsin. The tags meet federal standards but aren't required because of the cost.
Diederichs and his partners, who have about 5,400 cows split between farms in Malone and Poy Sippi, began using them eight years ago in part because they save time. Workers with hand-held devices can scan the tags and immediately pull up animals' birth, medical and other records.
The tags also are important as companies like McDonald's want to know where their food came from and be able to trace it back, Diederichs said, adding, "I think that's going to be the bigger push" for others to switch.
The federal rules allow two states to agree on alternative forms of identification, such as brands, for use with animals shipped between them.
South Dakota rancher Kenny Fox said this is an improvement over the earlier program, but he still believes the federal government should recognize brands. Ear tags can fall off, but brands are a permanent mark of ownership, he said. And brands can be registered and assigned a number in computer systems so that they can be quickly tracked back to a farm or ranch.
Fox, the animal identification committee chairman for R-Calf USA, an advocacy group for ranchers, said the program won't mean a big change in practice for him. He has about 500 cows plus their calves in Belvidere, S.D., and already tags his cows as part of a program to control brucellosis, a disease that can cause pregnant animals to miscarry. But he also brands his cattle because the state recognizes brands as proof of ownership.
"It has been very beneficial to our operation," Fox said. "In the past, the inspectors have found three, four animals that belong to me that were mixed up with other people's livestock."
It would be nice, Fox said, if he could use brands for both livestock tracking and proof of ownership. But he added, "I'm thankful they didn't keep using the (earlier program). It just wasn't going to work out here in this country."