Cracks and lameness
Cracks almost never penetrate the entire thickness of the wall; they just exist in the outer layer, Clark points out. “The hoof matrix has a crack-diversion mechanism. As the crack penetrates deeper, it’s diverted away from going in a straight line,” he adds.
“The animal’s body responds to a crack by thickening the wall in that area, to protect itself. Often the worst-looking cracks don’t cause lameness. If you cut into a dead hoof, the wall in that area may be 2 to 3 times thicker than normal. If the wall gets very thick, you may also see remodeling of the bone, to accommodate the increased thickening. Some of these cracks persist for years,” Clark says.
“The way the hoof is formed, it’s like reinforced concrete. The hoof wall is made up of tiny tubules that run vertically, like rebar, which is why most cracks form vertically rather than horizontally; it’s the natural cleft between the tubules. But the crack diversion mechanism ensures that the crack doesn’t split inward,” he says.
“Once in awhile, however, the animal goes lame and you may find an abscess at the bottom, or deepest portion, of the crack. In my experience in 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, we often find an abscess somewhere else in the foot, rather than under the sand crack,” Clark says. Usually the crack is incidental.
“Our usual advice is that ‘if it ain’t broke, don’t fix it,’ but if the animal is lame, you need to clean the crack out – grind it out or trim it – to try to get back to healthy horn,” Clark says. “The risk factors for crack formation still exist, however, so even if you get that one cleaned up, the chances of it reforming are high.”
Palpating the area over the crack, as well as the coronary band above it, is required to determine if a sand crack is painful. “If there’s an abscess, it will be hot. We use hoof testers to put pressure over the crack; if she winces, we suspect an abscess and clean it out,” Clark says.
Debriding the area (removing all damaged horn) and draining the abscess will relieve pain and lameness.
“I tell my students 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 – is there an abscess and where is it? If it happens to be in the sand crack, then we deal with the sand crack. In some cases, I’ve tried filling the crack with an epoxy, but I don’t think it really helps in the long run,” Clark says.
Sometimes, limiting the animal’s movement is required, Shearer adds. “If one side of the foot is better than the other, we try to stabilize it and take the weight off the affected claw. We may nail or glue a wood block under the healthy claw. If we get the weight off, the corium won’t continue to be traumatized, and will hopefully heal and start to produce new horn.
“The main objective is to stabilize the two portions of the wall that are loose and moving/pinching. Sometimes, the fragments are wired together,” he says.
“If the foot is overlong, we trim it back, and sometimes can remove the fragment, or a portion, so it won’t be flexing so much. This may provide the cow some relief from movement and pinching until the foot can grow out,” Shearer says.