Something that might help is a hoof conditioner for horses. I have a cow how's hooves tend to crack. The conditioner is like a lotion and helps to soften the hoof. This could help prevent cracks in the future. When my horses get cracks on their hooves, my farrier suggests applying merthialate (not sure of the spelling). It's an antiseptic for wounds that you can get at the pharmacy. Its in a little bottle with a plastic applicator. The stuff is pink when it gets on your skin. It helps keep the crack from getting infected.