Clearing the air about garlic.

Researchers question its equine benefits.

An article by Clare Illingworth, SPARK writer, University of Guelph.


There’s a stink being raised across the country about the practice of feeding garlic to horses in an effort to prevent respiratory disease. Garlic’s natural antibacterial properties have some horse owners hopeful, while others worry that its long-term use could be a dangerous fad; in fact, it might be toxic. Growing concerns have pointed the equine community to the University of Guelph, where researchers are trying to clear the air.

Prof. Mike Lindinger and graduate student Wendy O’Neill of the Department of Human Biology and Nutritional Sciences think there’s more than meets the nose when it comes to garlic’s healing powers related to respiratory diseases and other health conditions.

“It’s really critical that we investigate its usefulness to horses,” says O’Neill. “Research is beginning to show that garlic may have medical benefits in humans and other ani-mals, and it has already been used in developing countries.”

In the past, critics charged that commercial products containing garlic were ineffective. That’s because garlic’s active ingredient — allicin — is often missing from many commercial products that are heat-dried.

Paradoxically, garlic in its pure form can’t be deemed completely safe. It’s possible that the herb’s suspected antimicrobial proper-ties may — with long-term use — damage the beneficial hindgut bacteria vital to a horse’s digestive system. This could allow unfavourable bacteria to flourish, creating imbalances in the digestibility of forage and in the overall health of the gastrointestinal tract.

More important, says O’Neill, garlic has been shown to induce a type of anemia in dogs and sheep. In addition, onions (a rela-tive of garlic) are known to have toxic effects on horses, and it’s possible garlic could react the same way. So, before garlic can be consid-ered a safe antimicrobial agent, researchers have to investigate that potential for harm.

Once garlic’s safety has been established, the researchers will tackle issues surrounding infectious respiratory disease, a condition caused by bacterial and viral infection in the lungs. Affected horses are often treated with conventional antibiotics, but long-term use can cause digestive complications.

During their two-year study, the research-ers are using a combination of laboratory tests and animal studies to determine the absorptive profile, safety and effectiveness of garlic in horses.

“There are so many medical applications for garlic, but respiratory disease is the most prevalent,” says O’Neill. “This ongoing research will help horse owners understand whether garlic could be beneficial and, if so, how to use it.”

This research is sponsored by the Ontario Ministry of Agriculture and Food and the Ontario Horse Racing Industry Association.