Do Pre- and Probiotics Help Horses?

A nutritionist looks at the relevant, if limited, research about pre- and probiotics in the equine diet.

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Do Pre- and Probiotics Help Horses?
Photo: The Horse Staff

Q: I see a lot of supplements these days that contain pro- and prebiotics. Are they necessary, and will they benefit my horse?–via e-mail

A: You’re right, it’s common to find ingredients such as Lactobacillus acidophilus, Mannan-oligosaccharides (MOS), and yeast in a range of products, some not even aimed at gastrointestinal (GI) health. And when you look at products designed specifically to support GI health, the options are endless. The premise behind these ingredients is that they help support a healthy GI environment. The question: Do they really work?


The U.S. Food and Drug Administration and the American Association of Feed Control Officials define probiotics (sometimes referred to as “direct fed microbials”) as a source of live, naturally occurring microorganisms. Probiotics are fed with the goal of enhancing or restoring the beneficial bacteria in the GI tract and are frequently measured in colony forming units (CFUs)

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Clair Thunes, PhD, is an equine nutritionist who owns Clarity Equine Nutrition, based in Gilbert, Arizona. She works as a consultant with owners/trainers and veterinarians across the United States and globally to take the guesswork out of feeding horses and provides services to select companies. As a nutritionist she works with all equids, from WEG competitors to Miniature donkeys and everything in between. Born in England, she earned her undergraduate degree at Edinburgh University, in Scotland, and her master’s and doctorate in nutrition at the University of California, Davis. Growing up, she competed in a wide array of disciplines and was an active member of the U.K. Pony Club. Today, she serves as the district commissioner for the Salt River Pony Club.

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