Vitamin E  (natural/bio available)

Highly effective at a low dose, requires as little as 2 grams per 500Kg horse daily. 

Vitamin E helps muscles, nerves, fertility and immune function. Popular for high perfomance horses due to the powerful anti-oxidant properties which assist muscles. Vitamin E is a powerful anti-oxidant which helps to protect cell structures from damage. High performance horses require higher levels of anti-oxidants as they produce more damaging waste products during exercise.

Muscle issues:

6- 16 grams daily  (3000 iu - 8000 iu) for high performance horses/horses working at high metabolic rates

2-6 grams (1000-3000 iu) general dose for most horses in work

General dose of 2 grams (1000 iu) recommended when the diet is in shortfall, such as limited access to green pasture.

Please note: for horses prone to tight muscles; ensure sufficient electrolytes, selenium  (blood test first) and that the horse is conditioned also for the work required.