"White hoof syndrome" really is a fallacy
. I've owned a lot of white hooves over the years, if they had problems, so did the dark hooves.
While genetics do play a big part in hoof quality (TB's are notorious for having poor hooves, diet is crucial.
What goes in the feed pan, quality of hay, and if the horse has access to pasture. Grass is a two-edged sword for horses with metabolic issues.
My metabolic horse has naturally thick hoof wall which saved him when he foundered in 2012. I feed him NANRIC Extra Strength Biotin 100, which can be ordered on line from the NANRIC web site.
My other horse has always had hooves like a goat (including the white hoof) and has been barefoot most of his life. I feed him Omega-3 Horseshine which is processed flax and some added vitamins. His hooves have such a natural sheen the farrier once asked if I polished them; I replied "not in this lifetime, I'm a trail rider"
Also, FWIW, I do not feed any sort of cereals or grains to my horses. I stopped doing that many years ago.