H. Scott Gravlee, DVM, CNS of Life Data Labs says to address the relationship of nutrition and white line disease, we must not overlook the important observations made over the years regarding the disease and the predisposing factors.
BA brief history urney Chapman, a world-renowned farrier from Lubbock Texas, USA, became one of the foremost authorities on the condition back in the late eighties and early nineties. At that time, he began to see an alarming increase in the numbers of white line cases he encountered in his shoeing practice both in the U.S. and U.K. Burney determined that it was not a disease of the white line, but rather the result of a fungal invasion of the middle hoof wall. Burney named the condition “Onychomycosis” or ONC. The disease is also known as stall rot, seedy toe, hollow foot and wall thrush. At first blush almost everyone, including Burney, thought white line disease was found in environments that were poorly maintained. However, the more he encountered it he began to realise the disease occurred more often in clean, well-managed stables and barns. He also observed that there was no correlation to breed, colour, or front versus back feet, and that the initial stages were non painful and usually detected by the farrier during routine hoof care.
Current information
Today, we know a bit more about white line disease and recognise that all horses are exposed. The medial (middle) hoof wall is the structure affected by white line disease. The damage is caused by organisms commonly found in the environment, both bacterial and fungal. These organisms require a nutrientrich environment that is lacking oxygen to flourish. The outer hoof wall is more resistant to invasion due to its higher density and exposure to environmental oxygen, compared to the low density and lack of oxygen in the middle hoof wall. The third section of hoof wall, the inner hoof wall, is more resistant to invasion due to the proximity of live tissue in this area. The live tissue is not only oxygen rich, thereby inhibiting these opportunist anaerobic organisms, but also has infection fighting abilities.
Contributing mechanical and environmental factors
We know that often trauma to the hoof capsule creates bruising and bleeding. The damaged and leaking blood vessels create a good food source for the hoof–eating microbes. Other predisposing factors include a prior occurrence of an abscess or laminitis in which the hoof wall becomes full of holes and crevices, nail holes or hoof cracks allowing organisms to gain access, and high moisture environments which tend to soften the foot and allow the bacteria and fungal organisms an easier entrance into the hoof.
Contributing nutrition factors
Properly balanced nutrition and quality hoof supplements may strengthen the hoof wall, reducing the likelihood or severity of white line disease. No one has proven this fact more sufficiently than Dr. Susan Kempson, a noted equine nutrition researcher in the department of Preclinical Veterinary Sciences, Royal School of Veterinary Studies, at the University of Edinburgh. Dr. Kempson has conducted numerous electron microscope studies of the equine hoof wall. Electron microscopes use electrons rather than light to capture images and can magnify up to approximately two million times.
Selenium and copper
Dr. Kempson demonstrated with scanning electron microscope photos that a horse that had been supplemented with excessive selenium developed a lack of structure in the hoof horn. Sulphur is required to build the strong cross links necessary for healthy hoof horn. However, excess selenium substitutes in place of sulphur creates weak hoof structure.
In addition, the soil where the horse was living was very low in copper. Copper will help protect the horse from the detrimental effects of small amounts of excess dietary selenium.
The electron microscope photos also showed that the space between the cells had been invaded by bacteria. An interesting fact is that Dr. Kempson found that bacteria were the frontline invaders of the hoof wall, setting up the environment for the secondary fungal invaders. The several different species of organisms that have been isolated from infected hooves all have one thing in common, they thrive on the sulphur-containing collagen of the hoof wall.
In the this case, after three months of discontinuing the selenium and supplementing copper the horse returned to his normal activities.
Calcium
Bran is the high fibre product of grain processing (grain hulls). Whether from wheat, rice, oats or other grains, bran contains phytates. Phytates block the absorption of calcium predisposing the horse to a calcium deficiency and other mineral imbalances. Calcium is important in providing the glue for cellular adhesion in the hoof tissue. Therefore, hoof wall quality deteriorates with calcium deficiency. Calcium deficiency is often a result of diets high in bran and results in weak, crumbly hoof horn. The poor hoof wall quality creates holes and defects that allow the bacteria and fungi associated with white line disease to penetrate.
Vitamin A
Deficiency or excess creates a similar hoof defect pattern with the outer hoof wall flaking off and the appearance of hair growing from the hoof. The hoof wall is basically hair glued together; therefore, either an excess or deficiency of Vitamin A can result in poor hoof quality, predisposing the invasion of micro-organisms.
The information in this feature, explains many circumstances associated with white line disease. However, it does not explain the puzzle of why horses in a well managed facilities and the overfed horses often have some of the most challenging white line problems. In agreement with Burney Chapman’s observations, we suggest the horse consuming a high carbohydrate diet, especially a feed sweetened with sugars or molasses, is predisposed to white line disease due to changes in the hoof wall environment that are favourable for these hoof eating organisms. It is possible that the favourable environment is created by high carbohydrate/nutrient diets resulting in increased nutrient levels in the medial hoof wall, serving as an enhanced food source for the microbes. Controlling carbohydrates may prove to be a factor in preventing or treating white line disease. } For further advice and information: www.lifedatalabs.com, makers of Farrier’s Formula®