Big Head Disease in Horses: Calcium Deficiency
Big head disease, known formally as nutritional secondary hyperparathyroidism, occurs because of dietary mineral imbalances. Horses require a 2-to-1 ratio of calcium and phosphorus in their diets; when this ratio is upset, absorption of these minerals falters. Horses become calcium deficient when they consume too little calcium or when there is an excess of phosphorus, which blocks the absorption of calcium.
Big head disease was first noticed in horses owned by distillery workers. They fed wheat bran and other grain by-products from the brewing process to their horses. These products are frequently high in phosphorus and low in calcium. When the diets failed to supply sufficient calcium, the horses’ bones were robbed of the mineral in an attempt to maintain necessary levels in circulation, as calcium is required for all sorts of physiological purposes, including muscle contractions, nerve function, and blood-clotting.
The distillery workers noticed that the heads of their horses had abnormal bony growths and that the bridges of their noses, between the eyes and muzzle, were misshapen and abnormally wide, thus the name “big head disease.” The bony distortions are actually fibrous growths formed to compensate for bone mineral loss. Additional symptoms include stilted gaits, tender joints, and loose teeth. If left unchecked, permanent skeletal damage occurs.
If the disease is caught quickly in mature horses, most of the damage can be reversed. The bones will remineralize once the diet is corrected. The disease is more threatening to young, growing horses because their bones have not finished growing and ossifying. The demineralization from inadequate bone calcium can cause permanent damage, making young affected horses unsuitable for a working life.
The most common diets associated with big head disease include concentrates or forages with high levels of oxalates, which are chemical compounds that “tie up” calcium, causing it to be unavailable for absorption from the gastrointestinal tract. Adding legume hay, a calcium supplement, or feeding a commercial concentrate with the appropriate calcium-to-phosphorus ratio can balance these oxalate-rich diets and prevent the disease.
One appropriate nutritional supplement for horses diagnosed with big head disease is Triacton, a source of highly digestible calcium that has been scientifically proven to increase bone density. In addition to its novel source of calcium, Triacton contains an array of bone-building nutrients: magnesium, silicon, iodine, boron, as well as several vitamins (A, C, D, and K) and organic minerals (copper, zinc, and manganese). Aside from the skeletal benefits of Triacton, the supplement supports gastrointestinal health by increasing the buffering capacity of the stomach and the hindgut.
Fortunately, very few cases of big head disease are seen today, especially in countries that rely on commercial feeds. Kathleen Crandell, Ph.D., an equine nutritionist at Kentucky Equine Research (KER), affirmed, “The disease was more common decades and decades ago when there was not an understanding of mineral balance, and horses were fed a lot of wheat bran. Since most people feed commercial mixed feeds these days, which will have added calcium, we see the disease less and less.” Working with a nutritionist can help horse owners steer clear of these problems.
Crandell does caution against adding large amounts of any phosphorus supplement to a commercial feed because it will disrupt the mineral balance in the diet. Misunderstanding supplementation can often cause overprovision of vitamins and minerals, Crandell said, and can lead to an unbalanced diet.
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