Hi, To fix the crack in the hoof you need to kill the bacteria. Vinegar is good at killing those bacteria and doesn’t hurt the hoof at all. You can get White Lighting at most tack shops (Farriers know about this product) and it is activated when you mix it with the vinegar.Read the instructions. It will fix the trush also. I soak for an hour in a boot. Do it twice a week and stop and see how it is before doing it again. To grow hoof faster to get rid of the crack you need to use Corona ointment. Rub Corona on the coronary band twice a day. Once in the morning and at night everyday. I used to work at a harness horse track and we would get horses with quarter cracks. I bought a draft/cross that had a bad quarter crack and my farrier said that I will not fix it because it was cracked all the way up to the coronary band but I did. Have your farrier groove out the bottom to take some of the pressure off of it. Good Luck.