Vitamin B12 is essential for red blood cell production, nervous system maintenance, and the activation of folate for DNA synthesis. Unlike many other vitamins, B12 cannot be obtained from plant foods — it is exclusively produced by bacteria. Fortunately, the microbial population in your horse's hindgut synthesizes vitamin B12 in substantial quantities, provided adequate cobalt is present in the diet (cobalt is the mineral building block that gut bacteria use to construct B12). This means horses rarely need dietary B12 from feed itself. B12 also plays a role in myelin formation, the protective sheath around nerve fibers, and in the metabolism of certain amino acids and fatty acids that support energy production.
Your horse needs roughly 20 to 30 micrograms of vitamin B12 per day — an almost invisible speck of powder. This is entirely produced by hindgut bacteria when sufficient cobalt (0.05 to 0.1 mg/kg of diet) is available. Horses grazing on cobalt-adequate soils or fed commercial feeds with trace mineral supplementation will produce all the B12 they need without any additional supplementation.
0.0% of daily nutrient intake
Vitamin B12 (Cobalamin) makes up 0.0% of your horse's total daily nutritional requirements by weight. That's a tiny amount — but it matters.
True B12 deficiency is uncommon in horses with a healthy hindgut and adequate dietary cobalt. Potential signs include anemia (pale gums, weakness, poor exercise tolerance), neurological issues (incoordination, hind-end weakness), poor appetite, and weight loss. Deficiency is most likely in horses with severe hindgut disruption or grazing on cobalt-deficient soils.
Excess is uncommon and not a practical concern. Vitamin B12 is water-soluble, and surplus amounts are excreted by the kidneys. B12 injections are sometimes given to performance horses, but there is no evidence of toxicity.
| Life Stage | Size | Min | Max | Unit | Notes |
|---|---|---|---|---|---|
| Adult | — | 0.02 | 0.03 | mg | For a 500kg horse. Expressed as 20-30 micrograms. Entirely produced by hindgut bacteria when adequate dietary cobalt is available. No dietary B12 source needed. |
Source: NRC 2007, general veterinary consensus
Cobalt is the essential mineral building block that hindgut bacteria use to synthesize vitamin B12. Without adequate dietary cobalt, B12 production drops regardless of how healthy the microbial population is. This is a direct precursor-to-product relationship.
What this means: Ensure your horse's trace mineral supplement includes cobalt, especially if grazing on cobalt-deficient soils. Adequate cobalt automatically ensures adequate B12 production without needing to supplement B12 directly.
