density of trabecular bone. Osteoporotic bone is more
than normal bone and is
predisposed to fracture.
Predispositions for osteoporosis include prolonged stall-rest, a cast or splint on an extremity, and an increase in non-weight bearing exercise such as . Clinically osteoporosis is seen as fractures occurring in situations that would not normally produce a fracture. Radiography reveals an increase in the size of the medullary cavity and trabeculae and a decrease in the density of the bone.
Diagnosis can be made through radiography or CT scan.
Treatment of osteoporosis is dependent on the cause. In cases of decreased weight bearing it is essential that weight-bearing activities be introduced as part of a controlled exercise plan to allow the stimulation of osteoblasts to lay down new bone. Rapid return to weight bearing exercise may cause fracture.
Prognosis varies depending on the cause.
Prevention is to maintain weight-bearing activities.
Nutritional Secondary Hyperparathyroidism (NSH)
NSH is a
bone disease that is considered rare in horses. It is also called “Big
head” disease, “Bran” disease or Millers disease.
This condition is caused by increase in parathyroid hormone production. There are 3 dietary situations that can lead to this increase:
Parathyroid hormone is produced in response to a in blood calcium levels. When the concentration of calcium drops the body must extract calcium from the bones. PTH and vitamin D work together to absorb calcium from the bones and intestines and excrete phosphorus in the urine. When phosphorus levels are high regardless of calcium levels, it reduces calcium absorption from the intestine as well as interfering with the conversion of vitamin D into its active form. Oxalates are compounds that to dietary calcium and prevent it from being absorbed. If this dietary imbalance continues for weeks/months, the persistent increase in PTH will lead to substantial loss of calcium from the bones. This can lead to osteoporosis, slow growth and affect bone development. In chronic cases, the body will lay down fibrous tissue below the periosteum to the bones. Diets that consist of un-supplemented grain such as oats or , with poor quality hay predispose for NSH. Horses that consume plants that contain oxalates, such as Seteria,
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