our feed has biotin in it it's called legends and triple crown and when the vet and farrier came they said it was probably where he mud is drying her hoofs out
To be honest, it's probably a lack of something in your horse's diet. I had a horse that has cracked feet to the point that she was lame lots the first year I had her, but I put her on a mineral supplement that had her feet looking top knotch within months. Biotin is essential, so look for a supplement with it in the mix.
I'd try the sealant and I'd make sure my supplement had a decent amount of biotin in it.
Put hoof sealant on it. Moisturizer makes them soft and loosen up and opens shoe nail holes. Apply Sealant to seal the cracks and holes. Hoofshoera Secret Hoof Sealant is my favorite.