It looks like it needs to be cleaned out daily and trimmed often to keep the pressure off of the toe (mustang roll). Make sure your farrier is coming out regularly to stay on top of the crack. Try white lightning soak or gel on the crack to kill the bacteria on the hoof. Smartpak carries White Lightning and you mix it with vinegar to activate the chemicals. Then let it soak for 20 minutes or so. Then apply white lighting gel on crack. This will kill the bacteria and allow the good hoof growth to grow down to the ground. If the crack isn’t opened up a little and treated and trimmed bacteria could start eating up the lamina causing white line disease or seedy toe, especially if the horse is in a moist or damp environment.
"Keep it Natural!"