Hoof Health Unveiled: What is Quarter Flare/Separation and how is it different from White Line Disease?
I get asked this question often from horse owners.
Let's talk Quarter Flare to start.
There are two issues that can cause the quarter to flare, first is mechanical stress placed on the hoof itself, the second is metabolic stress.
In a healthy hoof, the bond or interdigitation of the sensitive lamina to the insensitive lamina is tight. This connection is the white/golden line we see on the bottom of the hoof. The golden line is formed by the terminal papillae's around the rim edge of the coffin bone as they secrete a flexible type of keratin. This keratin (golden line) acts like a silicone bond between the two structures of lamina. Flexibility is key, as the insensitive lamina grows down and past the sensitive lamina that stays attached to the coffin bone itself. Because this bond must be flexible/elastic to join these two structures, it is the weakest part of the horse's hoof. This bond can be broken by mechanical stresses put on the hoof.
Mechanical stress is created when the hoof is allowed to grow too long, decreasing the ability of the frog to perform its role of providing support in the rear/center of the hoof, which then causes the full weight of the horse to push down on the hoof wall (peripheral loading). The weight and loading of the hoof wall can cause a great deal of leverage on the golden line which is how the quarter flare starts. As the wall moves away or flares, the golden line must stretch to cover the increasing distance between the two laminae. If the stress continues due to a long trim cycle or improper trimming, the golden line can break down, leading to the separation of the wall from the sole. When this separation happens, the golden line expands to cover this distance (lamellar wedge).
To treat quarter flare caused by mechanical stress a shorter trimming cycle should be implemented with regular maintenance trimming being performed every 2-3 weeks, allowing the frog and heels, to bear the primary impact of the footfall and not the hoof wall.
Metabolic Stress is a breakdown at the cellular level of the hoof. Systemic metabolic conditions such as stress, insulin dysregulation, PPID, obesity, mineral imbalance, dietary imbalance, or infection can cause a weakness within the cells of the hoof. This breakdown can cause issues within the hooves and the ability to create and maintain the strong bond between the laminae. Signs of metabolic conditions that show up in the hoof can be slow growth, angle changes to the hoof wall, brittleness, ridges, and fine line cracks in the hoof wall.
What is White Line Disease?
Any weaknesses of the lamellar attachment can lead to microscopic openings for fungi and bacterial microbes to gain entry which can lead to infection. This infection can result in large cracks and chips, and separation as the golden line (the “silicone” that joins the sole and hoof wall) gets “eaten” away. As this bond weakens and if any metabolic conditions, improper trimming techniques or long trimming cycles are not addressed and corrected this can lead to the development of White Line Disease (seedy toe) in the hoof.
The best defense against White Line Disease is prevention! Do not let the hoof wall peripherally load the hoof, and make sure any wall leverage is kept to a minimum with a good balanced trim and trim schedule. If you see a small cavity or separation in the golden line, make sure to first address the leverage that likely caused it, and second treat the area topically to prevent the microbes from taking over. My favorite treatment for non-invasive separation is to gently remove any debris from the area and to apply Artimud into any cracks or crevices that are present. For serious, invasive (more than a few mm of separation) cases of white line disease that are eating up into the area, I soak the hoof twice weekly with White Lightning, a liquid soaking solution first and then treat topically with Artimud for turnout.
Remember, quarter flaring, separation, and white line disease are all secondary conditions that are caused by leverage or a weakness within the hoof. First, address the cause of the weakness, and you will likely resolve the secondary issues.
Kristi Luehr is a barefoot trimmer/farrier, author, and founder of the Okanagan School of Natural Hoof Care. She is certified by the Canadian Farrier School as well as the Oregon School of Natural Hoof Care, and also has certification in equine massage and dentistry. Her focus is to educate owners about hoof anatomy, function and proper barefoot trimming that supports and grows healthy and functional hooves specific to each horse's individual needs. She is the author of three online courses specific to hoof care and is always striving to create more educational content for students to learn from.