Amount of daily calcium (Ca) intake have direct impact on bone metabolism, because of an important mineral component of bone. Two months rearing with less than 0.3% Ca diet clarified effectiveness for a rat model of osteoporosis, resulted in a significant decrease in BMD and bone strength. Besides low Ca diet associated with ovariectomy also induced significant decrease in BMC and BMD in such a short-term. Otherwise precaution for assessment as to an experimental objective ought to be deliberated depend on which part of bone should be evaluated and how long rats should be reared.