Nutritional Secondary Hyperparathyroidism is commonly known as “Big Head” or “Bran Disease” and it occurs when there is a calcium imbalance within the horses’ diet. Calcium is of one the most important minerals required in the horses diet to maintain strong, healthy bones and teeth and to aid muscle and nerve function. It is essential that a horse’s diet is balanced and maintains a calcium phosphorus ratio of 2:1 to maintain good health and well being.
Big Head condition can occur in horses when they are:
Grazing tropical and sub-tropical grasses that contain high concentrations of oxalates. Kikuyu, buffel grass and setaria contain substances called oxalates which act to bind calcium, rendering it unavailable for absorption from the gastrointestinal tract.
Fed high phosphorous containing diets such as high grain or bran. Grains and bran are high in phosphorous and low in calcium and also contain chemicals called phytates, which bind to calcium in the gut, forming calcium-phytate compounds that cannot be absorbed by the horse.
Clinical signs can include, but are not limited to the following:
Enlarged or swollen facial bones (particularly above and behind the facial crests) the nasal bones can occasionally be obstructed resulting in respiratory “noise” during exercise.
Loose or shifting teeth and difficulty chewing
Ill-Thrift and a harsh coat
Failure to reach expected height in growing horses
Ligament and tendon injuries
Watery nasal discharge
Clinical signs occur due to the low absorption of dietary calcium. The phytates and oxalates prevent the uptake of calcium from the small intestine. The calcium complex then overflows into the large intestine. The fermentation process releases the calcium, but it is not absorbed efficiently from the large intestine of the horse. This results in a deficiency of calcium in the blood, although adequate levels may be available in the diet.
Low blood calcium triggers the release of the parathyroid hormone, which acts to demineralise calcium from non-weight bearing bones of the face and pelvic structure. Chronic demineralization of the facial bone results in the development of Big Head, with distortion of the nasal bones.
Prevention and Treatment
Restoring the correct balance of calcium and phosphorous within the horses blood stream is imperative in the treatment and prevention of big head disease. A calcium supplement such as Hyfeed Big Head Pellets or Big Head Lick should be used to rectify the calcium:phosphorous ratio and overcome calcium deficiencies. Growing horses, heavy sweating horses and pregnant or lactating mares should be of particular concern as these classes of horses are more predisposed to calcium deficiency and require higher levels of supplementation.
Clinical signs such as lameness may resolve within 4-6 weeks depending on the severity, appropriate supplementation & adequate dietary provisions. In severe cases, remineralisation may take up to 12 months and during this time horses should be considered unsound and not fit for riding. Veterinary diagnosis and X-ray should be considered to eliminate other possible causes of enlargement of facial bones.
Big Head pellets and Big Head Lick combat the effects of big head disease by helping to restore calcium levels within the blood. Containing a 3:1 calcium phosphorus ratio feeding Big Head pellets/Lick ensures that maximum calcium absorption occurs. Big Head pellets/Lick is suitable for all horses on problem pastures or feeds and can be used as a preventative or treatment of big head disease symptoms. In addition Big Head pellets act as a supplementary energy source and contain essential vitamins and trace minerals to aid the horse during the recovery process.
It may not be possible to remove horses from problem pastures but now, thanks to Hyfeed Big Head pellets and Big Head Lick it is possible to manage horses at risk of Big Head without complication and with confidence.