Nutritional secondary hyperparathyroidism

Veterinary advice should be sought before applying any treatment or vaccine.

Nutritional Secondary Hyperparathyroidism

Big Head, Bran Disease, Miller's Disease

NSH is a metabolic bone disease of horses, caused by a calcium deficiency. The deficiency is the result of horses consuming a diet with excess phosphorous (more than 20% of rations contain wheat-bran based feeds), or ingestion of fresh pasture grass, weeds, hay, or receiving large quantities of treats that contain large amounts of oxalates (oxalic acid).

Upon ingestion, oxalates bind calcium (Ca), magnesium (Mg) and other trace minerals such as iron (Fe), making them unavailable for absorption by the small intestine. This leads to disturbances in the Ca/P ratio and results in excessive mobilization of bone mineral. By demineralizing the bones, the horse becomes weakened and misshapen, resulting in deformation of the face and lameness.


Swelling of the lower jawbones
Loose teeth
Vague, shifting, intermittent lameness
Short, stiff gait
Weight loss
Poor body condition
Reduced growth


  • History
  • Clinical signs
  • Physical exam
  • Dietary analysis
  • Laboratory tests



Increasing calcium intake to two or three times maintenance for 2 weeks
Increase calcium to supply horse's maintenance needs to restore ideal calcium-phosphorus ratio
Stall rest
Removal from pasture with oxalate-containing plants


  • Feeding horses a balanced diet
  • Removal of oxalate containing plants from pasture or hay
  • Performing periodic grain, soil or hay analysis to check nutrition balance
  • Supplementing diet with additional calcium

Scientific Research

General Overviews

  •  icon
  •  icon
  •  icon
  •  icon

Age Range

Horses that are 7 years of age and younger are most frequently affected by NSH.

Risk Factors

  • Diets supplemented with large amounts of wheat or rice bran
  • Consuming hay or pasture grass (usually tropical and subtropical grass species) with high levels of oxalates
  • High number of oxalate accumulating weeds in pastures or hidden within haybales