Cobalt is a trace mineral whose primary importance in your horse's body is indirect: hindgut bacteria require cobalt to synthesize vitamin B12. Without adequate cobalt, B12 production drops, leading to impaired red blood cell formation and energy metabolism. Horses cannot use inorganic cobalt directly — it must first be incorporated into B12 by gut microorganisms. Cobalt-deficient soils exist in certain regions, and horses grazing exclusively on pasture from these areas may develop subclinical B12 deficiency over time.
Your horse needs approximately 0.5 to 1 milligram of cobalt per day — less than a speck of dust. For a 500kg horse, the NRC recommends about 0.05 to 0.1 mg/kg of dry matter intake. Most trace mineral blocks and commercial feeds include cobalt, making supplementation straightforward. If your region is known for cobalt-deficient soils, ensure your mineral supplement includes cobalt.
0.0% of daily nutrient intake
Cobalt makes up 0.0% of your horse's total daily nutritional requirements by weight. That's a tiny amount — but it matters.
Signs mirror vitamin B12 deficiency: anemia, poor appetite, weight loss, rough coat, and reduced stamina. In severe cases, incoordination and hind-end weakness may develop. Deficiency is most likely in horses on cobalt-deficient pastures without supplemental minerals.
Cobalt toxicity is possible but uncommon at dietary levels. Very high cobalt intake can cause reduced feed intake, weight loss, and anemia — paradoxically similar to deficiency signs. The NRC upper safe limit is approximately 25 mg/kg of diet, far above normal intake.
| Life Stage | Size | Min | Max | Unit | Notes |
|---|---|---|---|---|---|
| Adult | — | 0.5 | 1 | mg | For a 500kg horse. Required for hindgut bacterial B12 synthesis. Most trace mineral supplements and commercial feeds include adequate cobalt. |
Source: NRC 2007
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.
