Founderguard is a granular feed additive.
Its active ingredient is Virginiamycin.
The dose rate is 5g/100kg bodyweight (1/6th oz / 220lbs bodyweight) which is fed daily with food.
Trials have not been done to assess the safety of Founderguard in horses used for breeding.
It is advisable to introduce Founderguard gradually over 3-5 days to allow to hindgut to adapt gradually.