Several animal species have the ability to synthesise Vitamin C from glucose in the liver and the horse appears to be one of these. No deficiency disease has been recorded and no dietary requirement established for this vitamin in horses. Oral Vitamin C is poorly absorbed by the horse and where supplementation was desired experimentally, the intravenous route was the most effective at raising blood concentrations.
It has been suggested that synthesis by the liver may be insufficient in certain conditions such as strangles, influenza, recurrent airway disease, post operatively or following trauma or for ‘’bleeders’’. In such circumstances temporary oral supplementation at a dose of 30mg/kg bodyweight may possibly be justified. There is also a possibility that such supplementation might suppress the body’s own production by the liver, so withdrawal should be done gradually.