Dolly had dreadful feet when I got her nearly 4 years ago. I tried almost all of the usual hoof 'mixes' for about 2 years, plus other supplements for her sweet itch. Very little difference, if any at all frankly. Now with trial and error I have her sweet itch well under control and have gone from having to give her a steroid jab twice during the summer to just keeping rugged and her belly line covered, her feet hardly able to keep a shoe and very under run heels and cracked and flaky feet, too lovely hooves that keep a shoe very well and have to be really tugged off by my farrier at shoeing time.
My final choice of supplements were, Micronised linseed, brewers yeast, biotin plus from ebay, zinc, copper and magnesium. I have just recently changed from the biotin plus, zinc and copper, to an all in one Equimins Biotin 15......but her coat is looking rather flaky again so I will be changing to Equimins Biotin 25 to increase the zinc levels. I know Sox hasnt got sweet itch, but I can only say the combination I use, and it is for both the SI and her awful hoof condition.
My farrier cant believe how much her feet have changed in the lst year or so, but I have to say his input has also had a huge bearing on the overall improvement. A good farrier is to be hung on to at all costs, worth their weight in gold IMO.