What kind of ID do your horses carry? The 21st-century credential of choice is the microchip, a tiny electronic device implanted under the horse’s skin. Microchips are gaining ground over tattoos, brands, and other traditional ways of identifying horses, but there’s still confusion about them.

What It Is

A microchip, or radio frequency identification (RFID) transponder, provides proof positive of a horse’s identity. Each chip is preprogrammed with a unique identification number and encased in a clear capsule roughly the size and shape of a grain of rice. Your veterinarian uses a hypodermic needle to insert the device under the horse’s skin. The standard site is on the left side of the neck, midway along the nuchal ligament, which is just below mane. (There’s a video of the procedure at www.aaep.org/ microchip_video.htm.)

Once implanted, the chip is invisible. It does nothing and transmits no information until a hand-held scanner is passed over it. (Most vets, as well as animal-health officials, have the scanners.) The scanner sends out a low-power radio signal that activates the chip; the chip responds by transmitting its number, which the scanner reads. (For those who have privacy concerns, the microchips can only be read when close to the horse.) The number is registered to that horse and linked, in a database, to ownership information.

Who’s Using It?

While there are no statistics on the total number of horses with microchips, the devices are widely used in some areas. Louisiana, which requires positive ID for all horses as part of the state’s equine infectious anemia (EIA) control program, has been “chipping” horses since 1995; by some estimates 90 percent of horses in Louisiana now carry the devices. The chips are also common in other countries. Thoroughbred foals born in Britain and Ireland have been microchipped at birth since 1999. The European Union has adopted a new regulation requiring chips for all foals born after July 1, 2009.

Microchips are also part of a U.S. Department of Agriculture plan for a national animal tracing system, aimed chiefly at controlling outbreaks of disease. The goal of this voluntary program, called the National Animal Identification System (NAIS), is to trace sick livestock to their home base within 48 hours. A group comprising representatives from the American Horse Council, the American Association of Equine Practitioners, and the major breed and sport groups is helping to shape the program as it applies to the horse industry. So far the USDA has adopted most of the group’s advice, including its recommendation for microchip IDs.

Which Chip?

Several different microchips are on the market, and they don’t all operate at the same frequency. NAIS has adopted the frequency set by the International Standards Organization (ISO)—134.2 kHz—which is widely used abroad. Until recently, most chips used in the U.S. operated at 125 kHz. That caused problems because scanners made to detect those chips can’t detect the ISO chips. But scanners that read both types are becoming widely available, and ISO chips are becoming the preferred type in the U.S.

NAIS-approved microchips are encoded with a 15-digit number that starts with 840, the code for United States; these chips are sometimes called 840 devices. To get one, you first have to get a Premises Identification Number (PIN), a 7-digit code that identifies the place where your horses are kept. The USDA offers step-by-step instructions online at www.usda.gov/nais/840.

As of this writing, the USDA has approved microchips made by Destron Fearing, a Minnesota company, for use in horses in the NAIS program. (One version reports the horse’s body temperature along with its ID number, making it a useful tool for monitoring health.) The agency expects additional chip makers to apply for approval. The chips are available through veterinarians, breed registries, and other resellers. The Jockey Club, for example, issues ISO-compatible chips to owners of registered Thoroughbreds for $20.

Whether you get the microchips through your vet or another source, you’ll need a veterinarian to implant them. In some areas, local horse groups sponsor microchipping clinics, which could save on the vet bill.

Benefits

There are good reasons to consider microchips for your horses.

• Implanting a chip is far less painful than branding or tattooing—it hurts no more than a typical injection—and leaves no scar.

• It’s permanent. The ID number can’t be altered and stays with the horse throughout its life.

• The chip number can provide a link between horses and their official health records—certificates of veterinary inspection (CVIs), Coggins (EIA) tests, passports, and other documents required for interstate and international shipping.

• In a disease outbreak, officials can use the chip number to identify a sick horse and know where it came from. That can help establish (or rule out) quarantine areas and limit the spread of the outbreak.

• If a horse is lost or stolen, the microchip provides positive identification and a link to owner contact information. Widespread use of microchips in Louisiana helped reunite stranded horses with their owners after Hurricane Katrina, for example.

• Microchips can also tie horses to registry and other records. The chips aren’t likely to replace existing registration procedures, but the Jockey Club and many other breed registries are adapting their databases to link these records with microchip ID numbers.

Concerns

Can microchips fail or, worse, harm your horses? The most complete picture comes from the British Small Animal Veterinary Association (BSAVA), which has kept a database of adverse reactions since 1996. Only 361 of more than four million animals in the database had problems with their chips, a rate of less than one-one hundredth of a percent. The most common problem was migration of the chip from its original site. (Chips with a “biocompatible” plastic coating are less likely to migrate.) Chip failure and problems such as hair loss, infection and swelling were even more rare.

There have been reports that lab mice and rats developed cancerous tumors from microchips. However, the American Veterinary Medical Association (AVMA) points out that these mice and rats belonged to strains that are highly likely to develop cancer—they’re bred for cancer research. Tumors associated with microchips have been reported in two dogs, the AVMA says, but in at least one of these dogs something else may have caused the tumor. There have been no reports of chip-linked tumors in horses in the U.S. or abroad.

Will the NAIS require you to file piles of paperwork every time a horse leaves the property for a trail ride? That’s not the plan. As it stands, the program focuses on travel to venues where many horses come together, such as major shows, sales, racetracks, and the like. These are the kinds of places where diseases spread. Besides, you already need paperwork—CVIs, brand inspections, and so on—to send horses to these venues.

Adding a microchip number to these forms won’t change that. And knowing that the horses in your care carry permanent, positive ID could give you extra peace of mind.