I occasionally get calls from sometimes very upset horse owners saying that his or her horse needs immediate attention because the horse’s hoof wall is chipping – usually at the toe, or sometimes in the heel quarters. Most of the time, these calls originate with owners who have had the horse barefoot for some period, but whose farrier or trimmer doesn’t really have a solid understanding of proper hoof form. Most of my clients have heard these comments, but I thought I’d go ahead and share them with the rest of you…
When a hoof begins to chip, it nearly always means only one thing: the hoof is simply too long, and nature has begun to rectify the problem. As Jaime Jackson’s (and others’) studies have shown, the optimal hoof form – the shape that all of the forces at work on the hoof are continually moving the hoof towards – is very short, with a well-rounded edge. Therefore, if the hoof is too long and/or doesn’t have an adequate “roll” on the outer edge, nature will eventually address the problem to allow the horse to break over and move in a more efficient manner – hence, the wall begins to chip away to remove the excess length. When the farrier or trimmer properly balances the hoof, however, and the hoof has had a chance to progress further down the road towards its optimal form, chipping becomes much less common. In fact, one of the frequent comments from clients is that the hooves used to be chipped up all the time, but now never chip. So chips are never a reason to worry; they just mean the hoof is getting too long.
Cracks are a bit different. When a horse owner calls or writes about a crack, I always ask three things: 1) is there any bleeding from the crack, 2) is there any other fluid coming from the crack, and 3) is the horse lame. If the answer to all three is negative, then I reassure the owner that there’s very little cause for concern.
It’s my belief that cracks are caused by several different things. Probably the most common cracks are the ones that show up when the hoof is subjected to repeated periods of extreme moisture cycling – standing in wet snow all day followed by a dry stall all night, for example. These appear as shallow vertical cracks over much of the hoof’s surface, creating a very rough texture. They don’t cause any apparent problem, but don’t look very good. Once the moisture cycling stops, the hoof grows out normally.
Another common type of crack is the toe crack, where it extends through the entire hoof wall and is often accompanied by a small deviation in the white line. These appear to be the result of unnatural stresses at the toe because of excessive length and/or insufficient “roll” coupled with a compromised white line (“seedy toe”). I can’t say whether or not the stresses directly cause or contribute to the compromised white line, but I do believe that the compromised white line may be the consequence of the presence of some chronic, low-grade laminitis. Certainly, in cases of more severe laminitis, where there is considerable breakdown of the lamellar junction (“white line”), we see a very “stretched” white line all around the toe. Dr. Pollitt’s work has confirmed that this damage is entirely the consequence of the horse’s weight tearing apart the inflamed lamellar junction. It seems logical, therefore, to believe that in milder cases, we may see separation only at the point of maximum stress i.e. the toe. Once any separation occurs, debris begins to pack into the opening and work its way up the toe. The debris prevents good growth/attachment at that spot, and, when the spot is perpetually stressed during breakover, the crack occurs. Proper and frequent trimming to maintain a short toe with a correct “roll” will definitely help mitigate the stresses of breakover, but it may be helpful, and even necessary, to remove any debris to permit reattachment and growth. Plus, if laminitis does indeed play a role in these cracks, it necessarily must be addressed as well. One final point about this type of crack: if you examine a number of coffin bones, you’ll note that some, but not all, of them will have a “groove” up the toe. This groove may be entirely congenital, but may also be caused by some other condition – perhaps via the mechanism just described – post partum. And damaged or even absent sensitive lamellae in the grooved area may explain why some of these cracks never seem to go away, regardless of the treatment.
A third crack type, less common in my experience, is the one found in the heel quarters. These cracks, along with other “miscellaneous” cracks, seem to have two causes: 1) torsional (twisting) stresses in the hoof wall caused by improperly balancing the hoof – often the result of someone trying to do “corrective” trimming/shoeing on a horse, and 2) stresses caused by external factors such as stepping on a rock of just the right shape at just the right spot on the bottom of the foot, or a weakened wall due to nail holes from shoeing. The hoof wall is generally the thinnest in the heel quarters, which makes it most susceptible to cracking under these circumstances. Sensitive tissue can indeed be affected, which makes cracks of this type the most likely to cause lameness. Treating them requires treating the soft-tissue injury as with any other wound, if present, and relieving the underlying stresses by properly balancing the hoof.
And that’s the word on chips and cracks!