his study is to observe the different mechanisms of bone growth disorders caused by vitamin D and calcium deficiency. Our results showed that the bone densities

bone mineral and calcium contents

as well as bone weights

lengths and widths were decreased

while serum alkaline phosphatase levels and growth plate thickness increased in both calcium deficient and vitamin D deficient chickens

bone disorder are more serious in calcium. deficient diet group (C group). These studies demonstrated that calcium deficiency ant Vitamin D deficiency may induce dismineralisation and osteoporsis in long bone. The seriousness of bore disorder are different in elder chickens and young chickens. VitD deficiency can not canse chondrocytes cloumn disorder in elder chickens

but it do in young chickens. Maybe the mechanisms of bone growth disorder caused by vitamin D

calcium deficiency are different in different age of chickens