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Bran disease is a commonly used name for Nutritional Secondary Hyperparathyroidism (NSH), as is Bighead disease. This is a disorder characterized by weakened bones, symmetrical swelling of the bones in the face, and replacement of the bone by fibrous tissues. Although feeding an excess of unfortified bran mashes is a frequent cause of this disorder, it is not the only origin; horses may also develop Nutritional Secondary Hyperthyroidism from diets high in other sources of grain or from excessive grazing on grasses that are high in oxalates such as buffel or green panic grass.
Bran disease, or Nutritional Secondary Hyperparathyroidism, is a disorder caused by an imbalance of calcium to phosphorus in the horse's diet, sometimes caused by an overabundance of low calcium, high phosphorus bran in the diet.
Symptoms of this disorder occur more quickly in horses that sweat heavily, and horses with high calcium demands, particularly pregnant or nursing mares. These symptoms can include:
Bran mashes are made from the outer seed coat of a grain, and although most grains can be made into a mash, the most commonly used grains for horses are wheat and rice. Wheat bran is the most traditional ingredient for bran mashes and is particularly suited to adding phosphorus to the diet for equines who are deficient. Although it is important to introduce any changes to the diet slowly for horses, it is particularly crucial with wheat bran as adding it too quickly often produces a laxative effect due to the high amount of fiber. Rice bran is particularly useful for adding unsaturated fats to the diet, however, because of the high amount of fat in rice bran it is essential to get stabilized rice bran, or it goes rancid quickly.
Bran mashes may be recommended for horses for a number of reasons, and can be healthy and in some cases, helpful. When fed in excess, however, it can cause an imbalance in the calcium and phosphorus levels in their bloodstreams, particularly when combined with grass hay as their forage. As bran is low in calcium and high in phosphorus, it prevents the horse from absorbing enough calcium in the blood, weakening the bones and causing swelling in the bones of the face and head. This disorder is particularly detrimental for horses that are still growing.
Your veterinarian will most likely start the visit with a full physical examination, with particular attention paid to the structure of the legs and face. As horses often show signs of lameness with this disorder, the veterinarian examining the animal may also conduct a lameness exam to evaluate the animal moving at different gaits. Standard tests, such as a complete blood count and biochemical profile will help to establish if any infections or toxins are present, and a lactic acid test will help to rule out laminitis.
Standard tests such as a biochemical profile and a urinalysis may help to uncover this disorder by exposing either low calcium or high phosphorus amounts in the blood and urine, but these tests may not give an accurate representation of the body calcium levels. X-rays will help to rule out other disorders of the bone, check for fracturing, and to establish the amount of depletion that has already taken place.
The primary treatment for Nutritional Secondary Hyperparathyroidism in horses is an adjustment of the diet. When this disorder is caused by an overabundance of bran in the diet, reducing the amount of bran is not the only way to compensate for the lower calcium levels in comparison to the levels of phosphorus. Adding high calcium grasses such as legume grasses to the diet will help to improve the calcium intake and absorption, and calcium supplementation may help provide balance as well.
Limestone and dolomite are typically utilized to add supplemental calcium to the patient’s diet, but the amount of these supplements should be determined by a veterinary professional as the amount needed can vary by the horse’s specific situation and by the season. The supplement should not be added to the bran itself, as the properties inherent in the bran itself may bind the calcium, making it unavailable for the horse to use. While treating your horse, it is important to check the pastures they graze to ensure that oxalate containing grasses cannot contribute to the problem and high phosphate fertilizers should be avoided in grazing areas.
Poor condition and lameness are usually corrected within four to six weeks of the corrected diet, however, enlarged facial bones may or may not reduce in size. Although the horse may appear sound at this time, it typically takes around nine to twelve months for the bones to regain their former strength. X-ray technology and blood and urine tests will help to assess the patient’s response to the treatment, and until your veterinarian indicates that the horse is fully sound and the bones have been remineralized the horse should not be ridden. The prognosis for horses who experience this disorder when they are young may be more guarded as the bones may not develop correctly during their growth phase.
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