I don’t think you can get rid of a crack. You will have to wait for it to grow out. However, Smartpak makes a great supplement called Smartsox which increases blood flow to the heel and hoof area. Using a supplement like this may allow your horses hooves to grow out faster. I give the supplement to my horse that had thin soles and was lame. Now she is barefoot and sound. I also give her a biotin based supplement to keep her hooves strong. The combination of supplements has worked really well for us.