Thiamine is essential for nerve function and energy metabolism, particularly the processing of carbohydrates into usable energy. Horses obtain thiamine from both dietary sources (grains, hay) and synthesis by hindgut bacteria. Thiamine has a reputation in the equine world as a calming supplement, and some competition riders use injectable B1 before events, though scientific evidence for a calming effect is limited at normal doses.
A 500kg horse needs about 30 milligrams of thiamine per day — roughly the weight of a few grains of salt. This is well supplied by a standard hay-and-grain diet combined with hindgut bacterial synthesis. Supplementation is only necessary if your horse has been exposed to bracken fern or other thiaminase-containing plants.
0.0% of daily nutrient intake
Vitamin B1 (Thiamine) makes up 0.0% of your horse's total daily nutritional requirements by weight. That's a tiny amount — but it matters.
Loss of appetite, weight loss, incoordination, muscle tremors, and in severe cases, neurological symptoms. Deficiency is very rare in horses on a normal forage-and-grain diet but can occur if horses consume bracken fern, which contains a thiamine-destroying enzyme (thiaminase).
Thiamine is water-soluble and excess is readily excreted. Toxicity from dietary sources is not a concern.
| Life Stage | Size | Min | Max | Unit | Notes |
|---|---|---|---|---|---|
| Adult | — | 30 | 60 | mg | For a 500kg horse. Met by diet and hindgut bacterial synthesis. Supplementation only needed if horse has consumed bracken fern or other thiaminase-containing plants. |
Source: NRC 2007
