Those aren't really cracks. Pete Ramey refers to them as 'fissures'. They're simply symptoms of wet/dry weather. Even the best hooves get that, but they do require some attention. Pete Ramey has a spot in his DVD where he talks about those, while 'finishing' a trim. He lightly rasps over them with a finishing rasp in order to prevent infection from sitting in there, but only does that when the weather is supposed to remain dry for a long time
and there's no chance of the fissures reforming quickly. (Otherwise you'd just be rasping off hoof wall only to have the problem come back, where you rasp off more hoof wall only to have the problem come back...you see the pattern.) If you want to treat those fissures, you can put a little triodine over them, but DO NOT oil the hooves or seal them! Those fissures need access to air so that nothing gets trapped inside of them. I'd be more concerned about the horizontal rippling in the hoof wall - looks like that's new? Has his diet changed? That usually indicates areas where the laminae have tightened and released due to sugar overload and various diet changes. Iron and sugar overload are the two things you really want to avoid for better hooves, and then make sure vitamins and minerals are balanced with access to good forage. Other than that, the wall growth looks pretty straight from the side. I'd be interested in seeing more photos of those hooves. I'm wondering if those heels are high and putting torque on the toe wall (that could also influence wet-to-dry weather cracking.)
The authors of The Essential Hoof Book don't even use the term seedy toe...
This might be why 'seedy toe' isn't mentioned. It's not necessarily WLD. I read somewhere that the term seedy toe was originally coined in draft horses that worked fields or were on pasture often. Draft horses typically, on the bottom of the hoof, have a 'carina' (sp?) in the toe, or a divot. (That shape is actually mirrored in the coffin bone, according to Pete Ramey.) That visible divot on the bottom of the hoof can become stuffed full of dirt and grass seeds, so draft horses would literally be growing grass out of their hooves...back in the day. And yes, this could cause a WLD type infection, but it in and of itself is not WLD. My mare is half Shire and gets those carinas in damp weather...gotta keep em clean. I'll likely try a hoof wall sealant of some sort this year and see if they come back or not. (Edit:
jumpin in ahead of me here
(See pt. 8 for the 'carina' I'm talking about.)