Microchip Safety in Horses Evaluated

As microchipping becomes more prevalent in horses—and even obligatory in some countries—researchers are looking into the effects and usefulness of these foreign objects implanted into horses' bodies.

Microchip implantation appears to cause relatively little physical or physiological damage to horses, said Manuela Wulf, BSc, researcher at the Graf Lehndorff Institute for Equine Science in Neustadt, Germany. And for the most part, they’re a reliable source of identification, even if readability isn’t always 100%.

“Readability of the chip has a lot to do with the kind of scanner that’s used for reading, as well as how the chip was actually placed into the horse,” Wulf said.

In small animals such as cats and dogs, microchips are placed under the skin via injection. In horses, however, it’s critical that the microchip is placed into the neck muscle itself, said Wulf. “Even in small animals, microchips set under the skin can migrate,” she explained. “I know of a dog that was microchipped over the shoulder; six years later, that chip is now under his belly.

“With horses, you really need to have the microchip embedded into the muscle or the nuchal ligament where it’s far less likely to roam more than a few centimeters,” Wulf said. The nuchal ligament is a thick ligament located along the top of the neck, spanning from the poll to the withers.

Even so, muscle growth can cause the chip to end up deeper below the skin surface as the horse grows, and this can cause readability issues with certain kinds of scanners.

Basic scanners usually have a capacity to detect chips at a distance of up to 7 centimeters, she said. Considering that chips are usually embedded at approximately 2 to 3 centimeters below the skin surface, the basic scanners are frequently sufficient.

However, in a recent study she carried out using 428 microchipped horses, the basic scanner only detected 90% of the microchips, Wulf said. A larger, more advanced model of scanner capable of scanning at a distance of 12 centimeters could to detect all 428 microchips.

“Foals are usually 3 to 6 months old when they’re initially microchipped, and you can have a lot of growth and muscular buildup in the neck as they get older, bigger, and more athletic,” she said.

To determine physical effects of the microchip, Wulf and her fellow researchers also investigated 35 horses with microchips at necropsy following euthanasia. The microchips were covered by a thin capsule of fibrous tissue, sometimes with a minimal amount of inflammation, in most of the horses, she said.

Previous research led by Wulf and Christine Aurich, PhD, also of the Graf Lehndorff Institute and the University of Vienna, revealed that the implantation of a microchip caused minimal stress to foals.

“Provided breeders and veterinarians are properly educated in how to implant a chip and in how to read it, and knowing that sometimes a larger scanner is necessary, microchipping should certainly be considered a safe and reliable identification method for horses,” Wulf said.

Disclaimer: Seek the advice of a qualified veterinarian before proceeding with any diagnosis, treatment, or therapy.