Research has shown that hoof wall growth was 50 percent greater in growing ponies that were in positive energy balance than in ponies on restricted diets with reduced body growth rate. It is a common observation that when horses gain weight on lush spring grass, they also grow hoof faster. Recent research has shown that increasing the dietary intake of fat has little effect on hoof growth rate or strength, but fat can be a valuable addition to the diet in the role of maintaining positive energy balance.
Aside from energy, a well-balanced diet will provide nutrients the horse requires for overall health and well-being, and these in turn will help fuel sound hoof growth. The hoof wall is about 93 percent protein on a dry matter basis, and high-quality dietary protein will supply the horse with the amino acids researchers have theorized are essential for hoof growth. Because of the composition of the hoof wall, most of the commercially available hoof supplements contain methionine.
However, methionine is just one of the amino acids contained in the protein of the hoof, and deficiencies of any essential amino acid can be as detrimental as a deficiency of methionine. Hoof contains high levels of cystine, arginine, leucine, lysine, proline, serine, glycine, and valine, and lower levels of methionine, phenylalanine, and histidine. When researchers compared the amino acid content of normal hoof and horn of poor quality, they found a linear correlation between cystine content and hardness in normal horn but not in poor-quality horn. The protein of normal horn contained higher levels of threonine, phenylalanine, and proline and lower levels of arginine than poor-quality horn.
Other research showed there was a clear difference between the distribution of two sulfur-bearing amino acids in the keratinizing epidermis of the hoof. Cystine was located mainly in keratinocytes of the keratogenous zone in the matrix and in the nucleated keratinocytes that formed the incompletely keratinized basal part of the primary epidermal laminae and covered the lateral surface of the outer, fully keratinized part of those laminae. Methionine was located primarily in the stratum basale and in the stratum spinosum of the matrix and in the secondary epidermal laminae of the laminar layer. The pathway that converts methionine to cysteine is thought to be imperative in the production of quality hoof.
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Protein-deficient diets lead to reduced hoof growth and splitting and cracking of the hoof, but it has been shown that diets intended to support more rapid growth of young horses do not necessarily maximize hoof growth. This suggests that the amino acid needs for general body growth and faster hoof growth are different, and scientists have studied this difference in search of the most important nutrients for producing better hooves.
Most of the emphasis on research on hoof growth and hoof wall quality has involved biotin. It is thought that the normal horse has a biotin requirement of 1-2 mg per day, and this can be supplied in certain feedstuffs as a component of commercial vitamin and mineral premixes or by intestinal synthesis by microorganisms in the large intestine. Biotin is a cofactor in a number of enzyme systems.
In other animals, chronic biotin deficiencies lead to lesions of the skin and other keratinized structures, and supplementary biotin was first used in pigs to treat hoof problems. Studies have shown that supplemental biotin at levels of 15-20 mg per day had positive effects on hoof quality in some horses, but does not assist all horses.
A German study on the long-term influence of dietary biotin in horses with brittle hoof horn and chipped hooves was conducted over periods from one to six years. Ninety-seven horses received 5 mg of biotin per 220 to 330 pounds of body weight daily; 11 horses were not supplemented with biotin and served as controls. The hooves of all horses were evaluated macroscopically every three to four months and horn specimens of the proximal wall were examined histologically and physically in 25 horses. The hoof horn condition of the biotin-supplemented horses improved after eight to 15 months of supplementation, while the hoof horn condition of most control horses remained constant throughout the study. The hoof horn condition deteriorated in seven of 10 horses after biotin supplementation was reduced or terminated. The horn growth rate of treated horses and of control horses was the same.
Biotin only improves the growth of new hoof horn, not existing hoof, so its effectiveness depends on reliable administration at recommended levels. Because of this, several weeks may elapse before a noticeable difference exists in new hoof growth near the coronary band. It should be noted that some horses respond more positively to biotin supplementation than others. Just because biotin supplementation fails to improve one horse's hooves, doesn't mean it will not help the next horse's hooves.
Obviously, nutrition is important in producing healthy, strong hooves. Almost as important is basic hoof care. A regular schedule of hoof trimming for barefoot horses and trimming/resetting for shod horses should be followed. Farrier care every four to six weeks is sufficient for most horses. Letting horses go more than about six weeks without a trim is asking for trouble, as longer hooves tend to chip and split. Even if the hooves are not greatly overgrown, a light trim and smoothing can sometimes keep small cracks from progressing. While many idle and lightly used horses can go barefoot, shoeing protects the hoof and will prevent excess wear on hooves that tend to chip and crack. The farrier should not file or rasp away the shiny outer hoof covering, as this tough layer of horn helps to hold necessary moisture in the hoof.
Hoof dressings are often touted as the cure for bad hoof condition, especially for horses that have dry, chipped hooves. Research has been conducted to find out whether the use of dressings has any impact, good or bad, on the hoof. A study at the University of Edinburgh examined the passage of moisture into and out of the hoof capsule. Researchers tested full-thickness samples from wall, sole, and frog tissues obtained from equine cadavers. The samples were taken from hooves in good condition (solid, no cracks) and in poor condition (visible cracks). In the samples from hooves in good condition, moisture penetrated less than a millimeter into any tissue. Samples from hooves in poor condition allowed much more penetration of moisture into and throughout the inner tissues of the hoof. These results indicate that there is a natural moisture barrier in healthy hoof tissue, and products claiming to moisturize the hoof can be expected to provide little benefit to hooves in good condition.
The ingredients in some hoof dressings can actually be harmful, excessively drying the outer hoof layers and leading to brittle tissue that can easily develop small cracks. Formalin, solvents, or tar-based products are ingredients with the potential to damage the outer layers of hoof horn. Such damage allows moisture to move in and out of the hoof more freely than in hooves with healthy outer horn. Lower strength has been measured in hoof tissue that is either too dry or too moist, so tampering with the natural moisture level is not thought to be advantageous. In addition, dirt and bacteria may enter the cracks, possibly causing infection.
Summing up hoof management, remember that good basic nutrition is the bottom line for hoof quality. Use a feed that is designed for the class of horse you are feeding, and feed according to the manufacturer's instructions and to desired body condition. Look for feeds that are balanced for macro- and microminerals. Commercial feeds should not be cut with oats, as this skews the nutrient balance.
If everything is being done from nutritional and farrier angles and hoof quality is still poor, it is worth experimenting with supplemental biotin, methionine, and zinc. Kentucky Equine Research recommends the use of Bio-Bloom PS, a dual-action supplement designed to promote and maintain healthy hooves and skin from the inside out.
Unfortunately, there is no quick fix and maintaining a good foot on a horse is a combined result of good farriery, good nutrition, good health care, and selecting for horses that genetically have healthy hooves.
Reprinted courtesy of Kentucky Equine Research. Visit ker.com for the latest in equine nutrition and management, and subscribe to Equinews to receive these articles directly.
1st Dam: Hot Water, by Medaglia d'Oro