Skip to content
PLEASE NOTE: You may experience errors on our site when using Internet Explorer. Please consider updating your browser, or download Google Chrome.

Ask the Vet: What Dose of Vitamin B1 is Right for Your Horse?

Posted on: March 24, 2010 by Dr. Lydia Gray

I have been using SmartB1 on my rather spooky nervous mare. It has had a calming effect on her — almost to the point of being too calm and relaxed. I have started giving her only half the recommended dosage when she is not being ridden and giving her the full dosage when I am riding her. My question is — is it safe to give my mare the 15g dose every day over an extended length of time or should it be used sparingly — only on days she will be ridden? I appreciate your help with this question. JP, Colorado

Dear JP,

The nice thing about B1 (Thiamin) or any of the B vitamins is that, being water-soluble, any excess is passed in urine and not stored in the body. The NRC Nutrient Requirements of Horses even says:

“Thiamin toxicity in horses does not seem likely and has not been reported.”

The NRC also reminds owners that while the bacteria in horses’ hindgut make most of the B vitamins horses require, additional B1 and B2 (Riboflavin) must be supplied by the diet. That is, the bacteria do not make enough of these two B vitamins to meet the horses’ daily requirements so they have to be provided in the feed.

You’re lucky that your mare responds so well to B1! Some owners have to experiment with several different products to find the one that works best in their horse. You’re already on the “what dose works best” part of the equation!

Since Thiamin is involved in carbohydrate metabolism and in the transmission of impulses along nerves it’s hard to say which of these roles is the mechanism of action for its calming effects. So I can’t tell you if giving your mare a half dose on days she is not ridden and saving the full dose for days she is ridden is a good strategy or not. If I were you, I would look back in my journal (you DO keep a journal on your horse, don’t you?) and see how long it took for the SmartB1 to work. If it had an immediate effect, then your strategy is probably a good money-saving one. But if it took two weeks or more to work, then giving her a full dose the same day you need her to be calm may not give it enough time to work.