Vitamin K
What it does
Vitamin K makes blood clotting possible and also plays a part in bone metabolism. The larger share is generated by the gut flora, so the ration usually only tops it up.
Why it matters
That blood clots after an injury is vital — and with an intact gut it is assured without help from the feeding. In ration calculation this is an item you check and tick off.
When it becomes critical
It only becomes critical in two situations: when the gut flora is damaged — through diarrhoea or certain medications — or when spoiled feed brings antagonists along. Regular dosing is not indicated in healthy horses. No toxicity limit is known for vitamin K taken in through feed in horses; menadione — a synthetically produced form of this vitamin — is dangerous only as an injection, and that is a decision for the vet.
How much a horse needs
The tables give no daily figure here. A level of 0.5 mg in each kilogram of dry matter counts as comfortably sufficient, and in practice the gut covers it anyway.
Needed for blood clotting and involved in building bone. The horse produces most of it itself — which is why it is sensitive to anything that disturbs the gut flora. ⚠️ The requirement figures below are the least certain in the whole reference section: the requirement has expressly not been determined unambiguously, but derived from comparison with other animal species. They are given here because a documented estimate is worth more than a gap — but they are not the same as a measured figure.
Cited values
| Type | Value | Unit / context |
|---|---|---|
| Requirement | 0.5 | mg/kg feed dry matter (derived from comparisons between animal species) |
| Requirement | 0.05 | mg/kg metabolic body mass per day (the same figure on a different basis) |
“Metabolic body mass” is a calculated figure, not a weight: body weight to the power of 0.75. For 600 kg that is about 121 — the requirement is multiplied by that figure, not by 600. That is why the number looks small even though it isn't.
Possible deficiency signs
- Impaired blood clotting.
- Because the horse produces most of it itself, a deficiency becomes significant mainly when the gut flora is disturbed.