Vitamin A toxicity: comparative changes in bone of the broiler and leghorn chicks.

Severe skeletal lesions were produced in both broilers and leghorns orally administered toxic levels of vitamin A (330 or 660 IU vit. A/g body weight X day) for 21 consecutive days. Hypervitaminosis A in broilers produced an osteodystrophy characterized by abnormal thickening of the proliferative-maturation zone, metaphyseal sclerosis, hyperosteoidosis, decreased number of osteoclasts, and parathyroid gland hyperplasia. In leghorns, the osteodystrophic lesions were characterized by a thin proliferative-maturation zone, a relatively thickened hypertrophy zone, flattened spindle-shaped osteoblasts, and osteoporosis. In both broilers and leghorns given excessive vitamin A, the osteogenic layer of periosteum in all bones was thin.