Hoof wall cracks are fairly common in cattle. These are usually divided into two categories—vertical (often called sandcracks) and horizontal. If the crack goes clear through the hoof horn, it causes pain and lameness.
Dr. Jan Shearer, Professor and Extension Veterinarian at Iowa State University, says vertical wall cracks are more common in beef cattle than in dairy cattle, but horizontal cracks are common in all cattle.
HORIZONTAL WALL CRACKS – Horizontal cracks that run parallel to the coronary band are common because they often represent a benign physiological change that creates mild disruption of hoof horn formation. They can result in severe lameness, however, if they become deep.
Rings around the hoof are very common because the hoof wall grows at different rates during various seasons and also for physiological reasons, creating growth rings—which may occasionally become cracks.
“Every time the cow calves she goes through a period where hoof wall growth slows greatly or stops. There is a physiological change, affected by her hormones and metabolism as she goes from a non-lactating to a lactating stage. Major changes occur and the epidermal growth factor receptors are either more or less receptive, and this is partly what influences hoof growth rate—and it’s all affected by the change that occurs at the time of calving,” explains Shearer.
“Some people would call it stress, but this is a very difficult word to define. I would rather say that there’s an interruption of hoof horn growth that creates a horizontal groove, or a growth arrest line—which is associated with calving,” he says.
The physiological changes begin prior to calving and continue into early lactation. “Formation of hoof horn during the transition period is a lower physiological priority, compared with initiation of lactation. The result is interrupted hoof growth that exhibits itself as a horizontal groove in the hoof wall. In some instances, hoof wear outstrips hoof growth,” he says.
If a cow has horns, this same change occurs in the horn growth. “If you look at the rings on her horns, they signify when each calf was born. If a cow has had 8 calves, there will be 8 rings on her horn. She doesn’t get an annual ring; the change occurs with calving,” says Shearer. These growth rings are consistently found in both beef and dairy cattle.
“Calves get a growth arrest line associated with weaning. You could say this is due to stress, but we don’t have a clear understanding of this. Growth arrest in the hoof horn is multi-factorial. There is certainly a change in nutrition (the calf is no longer getting milk), which may influence this to some extent. Weaning—the way many producers do it—is one of the most significant stresses for a calf,” says Shearer.
But you don’t see stress lines on calves’ hoof walls if you don’t actually wean them—when they go through a natural transition. In nature the calf continues to nurse the cow, and then she kicks him off before she gives birth to her next calf. By the time she weans him, she’s not producing much milk anyway. The big calf continues to stay with her, however, and has mama and the herd for companionship and security, and there is no emotional stress involved in this natural weaning process.
“Some small operations don’t wean the calves; the cows wean their calves themselves, eventually. In this kind of weaning, I’ve never seen a growth arrest line in the hoof wall, like we see with abrupt weaning,” says Shearer.
Seasonal changes are another factor in hoof growth rate. This may be partly nutritional (time of year when feed is more plentiful, with green grass) or due to longer hours of daylight. “Growth rate is affected by physiological factors and may not have as much to do with availability of nutrients as it does with number of hours of daylight. Some of these things are not well understood, but people need to realize that not all horizontal rings are indicative of disease,” he explains.
“Some rings are associated with disease situations or extreme changes in nutrient level or balance or availability, but it’s not always easy to determine how important these are. With horizontal growth arrest lines, we may sometimes see a true hardship groove, which is an extremely significant or deep horizontal groove—and we tend to associate this with something beyond the normal physiological changes,” he says.
This growth disruption may be due to disease. When horn formation resumes, a full-thickness crack sometimes develops. We are not always sure about the cause. These severe disruptions in hoof horn formation create distinct ridges and grooves. In the most extreme cases where the fissure is deep enough to create a full thickness defect in the wall, this lesion is often called a “thimble”.
When a deep crack gets down to the level of the corium—the sensitive “quick” underneath—it goes all the way through the horn. “The fragment below the crack may become separated from the hoof wall above it. As it is growing down the foot and wearing away, a deep crack may become painful because every time that fragment moves, it pinches the underlying corium tissues,” says Shearer.
VERTICAL CRACKS – These are often called sandcracks. “These are rare in dairy cattle. Less than 1% of dairy cows develop vertical wall cracks, but up to 64.5% of beef cows get vertical cracks. The majority of these cracks, more than 80%, occur on the outside claw of the front foot. The front feet carry a little more weight than the hind feet. The inside claw is slightly larger, and bears most of the weight,” says Shearer, but there may be more movement and strain on the outer claw.
“Some people have thought that cracks are possibly related to dryness, or the fact that front feet have a steeper angle than the hind foot and are thus subjected to more stress. Yet dairy cows have the same steep angle in the front feet,” he says.
Beef cattle travel on earthen surfaces (and rocks, and often very rough terrain) and in some cases the feet may be drying out too much. “But dairy cows are standing on concrete all day and rarely get vertical wall cracks. Based on the numbers, there seems to be a breed predisposition to wall cracks,” he says. Some family lines, in any breed, also have more tendency to cracking. In a certain herd, often the cows that develop vertical wall cracks are related.
“Other factors that are associated with vertical cracks include vitamin and trace mineral deficiencies. Some people have suggested that laminitis may play a role. Some of the reasons remain a bit of an unknown, however,” says Shearer. In some cases body condition may be a predisposing factor; heavy, overweight cattle may be more at risk. Age may also be a factor, since older cattle tend to have more sandcracks.
Selenium—either too much or too little—can have an adverse affect on hoof wall strength and growth. “There are many, many possible causes for cracks, and I don’t think we can rule out very many of them,” he says. Some of these factors may vary from cow to cow, regarding vulnerability.
TREATMENT – “Sometimes you need to limit the affected animal’s movement, so it doesn’t have to walk very far to feed and water. And if one side of the foot is a little better than the other, we may try to thin the horn or stabilize it in some way, and take the weight off the claw where the fragment is less stable. We may put a wood block under the healthy claw, to leave the cracked claw up off the ground so it won’t have to bear weight. If we get the weight off, the corium won’t continue to be traumatized, and will hopefully heal eventually, and start to produce new horn. Once it does that, it will self correct,” says Shearer.
“The main objectives in therapy are to stabilize the 2 portions of the wall that are loose and moving/pinching. There are a number of ways this can be done. Sometimes the 2 fragments are wired together, or stabilized by a variety of other means. Taking the weight off the most damaged claw will hopefully enable it to heal and stabilize itself. A wooden block can be nailed or glued to the other claw,” he says.
“There are surgeries that can be done. Sometimes the foot ends up with serious wall ulcers. Producers need to realize that only a small percent of hoof wall cracks actually cause lameness and need to be treated. But whenever the cracks cause lameness, they can be very complicated to manage—especially the vertical wall cracks. These can be hard to stabilize,” he says.
“If the foot is overlong, we try to trim it back, and sometimes we can remove the fragment, or a portion of it, by trimming. Sometimes we can trim it enough that it won’t be flexing so much. The key is to remove or stabilize it. Depending on how far down the foot it is, sometimes trimming alone can provide the cow some relief until the foot can grow out. It’s the movement and pinching that causes pain.” An overlong toe creates more stress and prying forces on the loose portion.