BIG HEAD DISEASE IN HORSES

Nutritional secondary hyperparathyroidism is a metabolic bone disease --a disease that affects bone metabolism.
It is often called  big head or bran disease.It has also been called Miller's disease.

Causes

• Insufficient calcium intake
• Excess phosphorus intake
• Eating plants which contains oxalates

Nutritional Secondary Hyperparathyroidism is seen mostly in horses grazing exclusively on grasses containing high levels of oxalate that locks up calcium, making it unabsorbable by the horse's intestines.

An excess of phosphorus affects the body stores of calcium in a few ways.

1.High levels of dietary phosphorus reduce calcium absorbtion from the intestine.
2.Excess intake of phosphorus results in the blood phosphate concentration.The phosphorus bind to the calcium in the blood stream,causing the blood calcium concentration to drop.
3.A high blood phosphates concntration also interfers with the conversion of inactive vitamin D to its active form.

Signs

• Enlargement of facial bones
• lameness
• Gait is stiff and stilted
• Physitis in young horses
• Neck pain
• Poor body or coat condition
• lethargy
• Poor growth
• In severe cases tearing of tendon,
• Bone fracture

Treatment and prevention

• Horses grazing oxalate containing pastures and those affected with clinical signs of bighead should be provided with daily calcium supplementation.
• Because NSH is a condition that results from dietary imbalance,treatment  and prevention must focus on correcting the diet
• Mineral and supplement mixtures that will provide the required amount of calcium and phosphorus for horses for a week include 1 kg rock phosphate mixed with 1.5 kg molasses plus 1 kg of a mixture of 1/3 ground limestone and 2/3 dicalcium phosphate mixed with 1.5 kg molasses.
• Calcium supplements
• Supplementation should be continued for 6 months or indefinitely if the horse is to be kept on the offending pasture. Lucerne hay is also high in calcium and should be given in addition to the calcium supplements.
• calcium can be provided through a variety of sources.
• But supplements also contains phosphorus ,such as dicalcium phosphate.
• Alfalfa is a very good natural source of calcium.
• In severe cases, affected horses should be confined to a stall .
• NSAIDS should be used with caution because reducing pain may inspire an increase in the horse's level of activity,which increases the risk of bone damage.
• The horse should not allow for a vigorous exercise even after recovery.

Reference

Lameness
Equine Research
by Christine King and Richard Mansmann