ive used the build up cubes but found my mare was allergic to it so had to stop using it, she holds her weight just as well if not better on grass nuts.
cant say ive used the super flex as ive only used the vet super flex when it was on trial
Used the feed and it was good for a mare we owned who used to drop weight in winter. Mare I look after now is on the Superflex and shes doing very well on it, she has spavin in both hocks.