Cracks in the hoof wall are fairly common in beef cattle. Dr. Chris Clark, associate professor of large animal medicine at the Western College of Veterinary Medicine in Saskatoon, says many older cows on the Prairies in Western Canada develop cracks in the hoof but you might not notice this unless the cow is lame. “You can expect to find sand cracks (vertical cracks that start at the ground surface) on almost 25 per cent of older cows. These cracks most commonly occur on the outside claw of the front foot, and the vast majority of these don’t cause any signs of lameness or ill health,” he says.
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“My colleagues and I here at the university have done some work on this, and we’ve looked at the feet of many cattle that have gone to slaughter. The sand cracks almost never penetrate the entire thickness of the hoof wall. They are just in the outer layer. The way the hoof matrix is built, it has what is called a crack diversion mechanism. As the crack penetrates deeper, it is diverted away from going in a straight line.” The pressure is dissipated outward and spread out rather than creating a deep split.
“The animal’s body responds to the presence of a crack by actually thickening the hoof wall in that area, to protect itself. Often the very worst-looking cracks don’t cause lameness. If you cut into a dead hoof and look at it, you might discover that the hoof wall in that area may be up to two to three times thicker than normal. Sometimes, if the wall gets very thick in a localized area, you may also see a bit of remodelling of the bone of the foot, to accommodate the increased thickening of the hoof wall. Some of these cracks can persist for years,” says Clark.
Causes
“We don’t always know why they happen. Actually this question was the basis of my master’s project. We didn’t come up with complete answers, but we did discover that hydration — the water content — of the hoof horn varies considerably throughout the year on the western Canadian prairies. In summer the moisture content of the hoof is fairly close to what I believe would be optimal. Even in dry years the hoof tends to pick up some moisture. But as cattle go through winter here, the hoof dries out,” he explains.
In the cold, dry climate, the feet are not exposed to any free water. There may be a lot of snow, but at very cold temperatures the snow is dry, not wet, and that moisture is not available. There’s no moisture in contact with the foot. “The humidity is very low here, in the winter. We took some hoof samples of cattle in February, when it is typically -30 C. There is snow, but it’s very dry. Those hoof samples were also very dry,” he says.
“As the hoof wall dries out, it starts to desiccate and become brittle. From studies that have been done on horse hooves, we know that as the hoof dries out, it becomes less pliable and more prone to breaking,” says Clark.
“We also discovered that cracks are more common in larger, heavier cows. We believe it has something to do with the physical forces of walking that particularly affect that outside claw on the heavier cattle. They probably have more force and strain on their feet, and if the feet are brittle they become prone to cracking in this particular area. The cracks are almost always at the front of the toe on that outside claw of the front foot. We think it is a local stress in this area that causes the hoof to crack,” he says.
One of the things he looked at was whether longer toes might make the claws more vulnerable to cracking, due to the added strain from the long toe. “We did find that the bigger feet were more prone to cracking, rather than the length of the toe, as the main factor. The volume of the foot was most important,” he says.
“The only thing we’ve ever seen published regarding what you could do to prevent cracking is that there’s some evidence that supplementing the diet with the B vitamin biotin may be beneficial. But that’s the only thing I’ve ever seen that suggests a way of preventing it. On the whole, I think cracks are mainly a consequence of raising cattle in certain environments,” says Clark.
There may be a genetic tendency toward cracking, as well. “One paper looked at this, trying to determine heritability of hoof defects, but this is a tough area to study. The researchers tried to demonstrate a genetic factor but were unable to find a conclusive link. This wasn’t a major study, but the only one I’ve seen,” he says. Some people feel there is a genetic link because often the animals that get hoof cracks in a certain herd are related. It may be due to the inherited conformation of the front feet. Hoof quality/horn strength in horses is definitely affected by genetic factors and this is probably true in cattle.
“I was going through some of the ancient books here in our university library, and found a horse book dating from the 1700s, which had a wonderful description of sand cracks in horses. It discussed the fact that these cracks were caused by keeping horses in dry, sandy areas. This illustrates the fact that after 300 years we really haven’t progressed very much in our understanding of these cracks. We do feel that cracks correlate with dryness in the environment, more than anything else,” says Clark.
“We took whole hoof samples from cows at slaughter houses — cows that did and did not have sand cracks. We did biomechanical testing of the hoof, and were unable to find a difference. There was certainly nothing about those animals’ hooves that seemed to make them more prone to cracking in a fracture mechanics test. The only things we found that made a difference were the position of the claw and the size of the claw. The front outside claw was most commonly affected. Those were the two biggest risk factors we could find, and the fact that the water content of the hoof really dropped off in the winter. There have been other theories proposed regarding causes, but the final conclusion of my master’s thesis was that drying was the biggest risk factor,” says Clark.
“The way the hoof is formed, it’s almost like reinforced concrete. The hoof wall is made up of tiny tubules that run vertically; they are like rebar in concrete. This is why most cracks form vertically rather than horizontally, because that is the natural cleft between the tubules. But the crack diversion mechanism usually makes sure that the crack doesn’t split inward but is diverted off to the side,” he says.
“Once in a while an affected animal does go lame and you may find an abscess at the deepest part of the crack. In my experience, dealing with lame cattle, the crack itself is rarely the cause of lameness. We see many lame cows, and the owner often thinks it’s due to the crack. When we trim the foot out, we often find an abscess somewhere else in the foot, rather than under the sand crack.” Usually an abscess is from a different cause, and the crack is incidental.
Treatment
“Regarding what you can do with sand cracks, our usual advice is the old adage: if it ain’t broke, don’t fix it. If the animal is lame, however, the owner may want to deal with it. You can clean the crack out — such as grind it out or trim it out — and try to get back to healthy horn. I am not convinced that this will absolutely encourage it to grow out and disappear. I think the risk factors for crack formation still exist. Even if you could get that one to clean up, the chances of it reforming would be quite high,” says Clark. The susceptibility of that animal probably hasn’t changed and the likelihood of future cracks is always there.
“I generally don’t worry about cracks unless they cause a problem. The only way you know if sand cracks are a problem is by examining the cow’s foot — to see if she’s sore when you palpate the area over the crack, and the coronary band above the area. If there’s an abscess it will also be hot. Then we use hoof testers, like we use on a horse. If you put pressure over the sand crack and she winces, then we suspect an abscess and we clean it out,” he explains.
Debriding the area and cleaning it out, getting to the abscess and draining it, will relieve the pain and lameness. It’s important to deal with the abscess, just like you would any abscess. “I always tell my students that it’s important to not focus on the sand crack when faced with a lame cow. Look at it like any other foot, and try to find the true cause of the problem — to see if there’s an abscess and where it is. If it happens to be in the sand crack, deal with the sand crack,” he says.
“If there’s an abscess under the crack, we simply open it up and use a very fine grinder to clean it up. We just remove all the damaged and underrun horn and smooth out the sides. In some cases, in the past, I’ve also tried filling the crack with an epoxy product, but I don’t think it really helps in the long run,” says Clark.
The hoof will grow out slowly. “The crack takes a long time to grow out. The hoof grows at a rate of about five millimetres per month. The average foot length is about 7.5 centimetres (3.5 inches) so it takes about 15 months for the wall to grow completely new horn, from the coronary band down to the tip of the toe. It’s a slow process getting it to grow out, and the risk for the crack reforming is quite high in those individuals,” he says.
Prevention
In commercial beef production, hoof cracks really aren’t much of an issue. It’s not economically feasible to deal with them unless they are causing lameness. They might be a cause of concern in a purebred herd, however, when the rancher is selling registered bulls and heifers.
“If someone comes to look at their animals, those breeders don’t want cracked feet. Even in those cases, however, other than telling the cattle breeder to try supplementing the cattle with biotin, I’m not sure what else to suggest — to minimize the cracks. They do seem to be a prairie issue and are not reported as often in other parts of the world. It’s primarily an issue in Alberta, Saskatchewan and Manitoba,” says Clark.
This type of crack is rarely found in dairy cattle and is much more common in beef animals. “Dairy cattle spend their time in a wet environment. Their feet are always exposed to manure and moisture, and don’t dry out,” he says.
