ABSTRACT
Rickets is a metabolic bone disorder characterized by osteopenic changes resulting
from the failure of calcification of the osteoid matrix and absent mineralization
of hypertrophic cartilage cells at the epiphyseal growth plates in growing primates,
herbivores, swine, carnivores, and birds. The causes of rickets include inadequate
dietary provision of calcium, phosphorus, and vitamin D. Osteomalacia in reptiles,
simian bone disease in nonhuman primates, and osteodystrophia fibrosa (secondary hyperparathyroidism)
or "bran disease" in herbivores are caused by a diet that has a much higher content
of phosphorus than calcium, combined with inadequate exposure to direct sunlight.
Medullary bone consists of interconnected spicules of bone resembling embryonic bone
and is established in relation to the shell formation cycle of laying birds. Hypertrophic
osteodystrophy develops in large-breed growing dogs, chickens, and guinea pigs and
is possibly caused by vitamin C deficiency. Tibial dyschondroplasia is a defect in
endochondral ossification characterized by a widened proximal tibial physis that is
not penetrated by metaphyseal vascular sprouts, commonly found in growing broiler
chickens, turkeys, and exotic birds.
KEYWORD
Osteodystrophy - medullary bone - dyschondroplasia - hypervitaminosis
