ANATOMY OF THE HOOF
microbes are what we call keratinolytic keratinopathogenic meaning they degrade the keratin of the hoof wall says Burns. As the keratin-loving microbes continue to multiply and spread upward through the hoof, they eat through the stratum medium which gradually opens a space between the stratum intern um and the outer lay ers progressive mented of the stratum wall. separation “This medium creates in of the the a nonpig- chronic hoof wall,” At first Burns the adds. farrier might see only a
at the toe or quarter during routine trimming and shoeing. Over time, the horse may develop mild soreness, detectable with a hoof tester, and the sole may become increasingly flat. Tapping the outer hoof wall with a hammer may produce a hollow sound. If the separation becomes extensive, the horse will become severely lame in that foot.
In a worst-case scenario, so few connections remain between the stratum internum and the stratum medium that they cannot support the weight placed on the hoof, and the strain on the soft laminae underneath may cause them to stretch and tear, allowing the coffin bone to sink or rotate downward. This is a potentially crippling condition known as founder. Once this happens, the horse may never be fully sound again.
The key to avoiding the worst effects of white line disease is to detect and treat it in its earliest stages, while the area of hoof affected is still small. That means monitoring your horse’s feet, keeping them clean and directing your farrier’s attention to anything you notice that might be abnormal---a widening of the white line, for example, with a powdery, chalky surface that flakes
away. If you’re unsure of what you’re looking at, take a photograph and send it to your farrier for an opinion.
Chances are, though, your farrier will be the first to notice a developing problem. “Horse owners are often limited in their ability to detect it because they are not doing the trimming,” says Todd Allen, CJF, APF, a farrier in Vandergrift, Pennsylvania. “It is usually up to the farrier to make the owner aware that it’s there.”
To treat white line disease, the farrier will first pare or scrape away the affected material, then treat the exposed area with some sort of disinfectant. “As soon as I see even a tiny spot or imperfection in the hoof, I treat it. If it’s a very small area, it might be just the size of a nail head, but you see the powdery telltale sign of white line disease,” says Allen. “Early on I try to do it in just a moderately invasive way, in hopes I can treat it topically and nip it in the bud. I tell the owner I will be conservative this time and see what it does, and if that doesn’t resolve it I may have to take it off.”
“Take it off” means resecting--cutting back---the hoof wall to remove all of the infected material and expose the underlying healthy surface. “If you catch white line disease very early, I think it’s preventable, but any time it gets a toehold you have to resect it,” Allen says.
At that stage, a veterinarian will need to be involved. “The veterinarian and the farrier can work together as a team, possibly using radiographs to determine the extent of the separation,” says Burns. “Cutting away the damaged portion of hoof wall and exposing the microbes to ultraviolet light and air is the most important thing.”
If the infection had progressed higher up into the hoof, the resection can be quite dramatic. But the farrier will need to continue cutting away hoof wall until he has exposed healthy tissue on all the margins. “You need to carve away the dead part of the wall and get all of it out, getting back into normal, healthy tissue,” says Steward. Typically, the resection stops at the epidermal layer---the sensitive laminae underneath are not exposed, and the resection does not bleed.
Depending on the appearance of the surface that remains, your farrier and veterinarian may also opt to apply some sort of antimicrobial treatment. “Anything that looks suspect should be treated with a topical medication, and what I use depends on what I see; there are a variety of products,” says Allen. These might include general antiseptics, as well as products labeled for treating other infections, such as thrush.
Your farrier will leave you with instructions for daily care of the treated hoof. You will need to keep the hoof clean and dry, and in some cases, reapply the topical disinfectant periodically. The horse’s turnout may need be limited, particularly in wet conditions, and his stall bedding will need to be kept dry. In subsequent visits, your farrier will track the progress of the hoof’s regrowth and make further treatment recommendations as needed. In difficult cases, he may consult further with your veterinarian. “Any time white line disease becomes refractory to normal treatment or is progressing even with treatment, we encourage the owner to get a veterinarian involved,” says Burns.
Because white line disease affects
middle layer of hoof wall internal layer of hoof wall white line apex of frog hoof wall coffin bone hoof wall sensitive (dermal) laminae insensitive (epidermal) laminae white line sole frog bulbs of the heels deep digital flexor tendon short pastern...
HEALING: To treat white line disease, a farrier removes the infected tissue and dead material from the hoof to expose the healthy underlying surface. He may then apply antimicrobial medication.