I use Farrier's Formula on my eventer who has really bad feet, really dry and crumbly and also the thinest soles ever. I didn't tell my farrier I was using it and after 5 months he said "see I told you they would get stronger on their own"!!!! It is quite expensive but really worth the money and...
I have heard they have gone bust. Probably because they were selling things too cheap! I tried them once, and hadrian supplies but have since found a company who is really fast to deliver and at good prices, and I even got a creme egg at easter!
There website is www.supplementsolutions.co.uk...
I have used Red Cell on one of my eventers and find that it really makes a difference to her energy levels at horse trials. Equine America make some xtra boost pastes which you can give on the day if you don't want to use a daily supplement.