80%)as a calcium supplement.Methods Weanling SD rats(21 days after birth,n=50)were fed with low calcium forage for 10 days,then were divided into 5 groups randomly with 10 rats in each group,half male and half female.GroupⅠwas control group fed on low calcium forage.GroupⅡ~Ⅲ were fed on low calcium with L-lactic acid calcium.Group Ⅳ~Ⅴ were fed on low calcium forage with ultramicro-mussel shell powder.The experiment period was 4 weeks.The indices were including the eventual weight and length of the rats,the calcium absorption rate of calcium supplement,the concentrations of serum calcium,serum phosphorus,bone calcium,skeletal muscle calcium,myocardial calcium,hemocyte calcium,liver calcium,kidney calcium and the activity of alkaline phosphatase were assessed.Results The effect of ultramicro-mussel shell powder group was similar to L-lactic acid calcium.Conclusion The ultramicro-mussel shell powder can be well absorbed and utilized,and it can be used as a calcium supplement.