Biotin : which is better naf or requisite?

I presume you are trying to supplement your horse's feet with biotin. You can feed biotin by the bucket and if there are not proper limiting amino acids in your horse's diet, it will not do any good. He will just pee it out and your money right along with it. To supplement hooves, you have to have the proper formula, not just one thing. the best thing for quality hooves is a proper diet. Nothing is better. If you need to improve growth, that is done with stimulation, exercise like riding and turnout.