Can Garlic Help Your Horse Fight Disease?

Garlic has been touted to have many health-related properties, from boosting your horse's immune system to repelling bugs just by the garlic odor in his sweat. In a recent study completed at the Equine Research Centre in Guelph, Ontario, a garlic metabolite showed antibacterial properties.

Wendy Pearson-O'Neill, president of the Nutraceutical Alliance, was an investigator in the study. Past research in humans indicated that garlic extract can kill some drug-resistant strains of bacteria as well as the fungus that causes ringworm. Furthermore, garlic extract seems to boost the antibiotic effect of drugs for meningitis patients. But little work has been done on garlic's effect on horses.

The biggest problem with garlic is the tremendous variability in the content of allicin, which is generally considered to be garlic's active compound. "How you prepare garlic has a profound effect on the allicin levels," O'Neill says. Furthermore, allicin has a half-life in blood of less than a minute, so many researchers think another compound in garlic might be the secret superhero. O'Neill investigated allyl mercaptan, a garlic metabolite with better stability.

Researchers applied allyl mercaptan to cultures of equine strangles bacteria. After 24 hours of incubation, allyl mercaptan did indeed inhibit bacterial growth when applied at a concentration that was the equivalent of feeding a horse 272 grams of fresh garlic, a helpful dosage baseline.

As most good research does, O'Neill's study raised a number of questions. Is allyl mercaptan well absorbed by horses? Which method of processing garlic might be the best way of preserving its activity? Could garlic's antibacterial properties give it the potential to disrupt the delicate balance of the beneficial hindgut bacteria, affecting a horse's ability to process fiber and manufacture B vitamins?

Another issue is the synergistic effect of garlic on some other drugs. Might this magnify their effects or make them linger in the system? Some AIDS patients reportedly use garlic to help extend the effect of drug cocktails. If something similar occurs in horses, there's the potential for drugs to remain at testable levels that were supposed to have cleared the system prior to competition.

O'Neill hopes to answer some of these questions with Phase II of her study. She'll be attempting to isolate and quantify allyl mercaptan in equine blood and lung fluid, which should show how well the compound is absorbed and whether it gets to the places where it can do the most good.

Is It Safe?

Although garlic is used by horse owners worldwide, the bulb's safety came into question when an article in a horse magazine intimated that it contained toxic compounds. Fortunately for the millions who administer garlic to their horses, the blame was misplaced; it's only onions that contain anemia-producing sulfur compounds, said Wendy Pearson-O'Neill, president of the Nutraceutical Alliance.

About the Author

Karen Briggs

Karen Briggs is the author of six books, including the recently updated Understanding Equine Nutrition as well as Understanding The Pony, both published by Eclipse Press. She's written a few thousand articles on subjects ranging from guttural pouch infections to how to compost your manure. She is also a Canadian certified riding coach, an equine nutritionist, and works in media relations for the harness racing industry. She lives with her band of off-the-track Thoroughbreds on a farm near Guelph, Ontario, and dabbles in eventing.

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