Measurement of bone quality in growing male rats using dual energy x-ray absorptiometry and bone ash content : a thesis presented in partial fulfilment of the requirements for the degree of Master of Applied Science in Animal Science at Massey University, Palmerston North, New Zealand

Growing male rats have been considered and used as a model for bone growth and prevention of osteoporosis because of their high bone turnover and demand for calcium. Dual Energy X-ray Absorptiometry (DEXA) is a useful tool for identifying minimal changes in bone mineral density and has recently been adapted for use in small animal models. The objective of this trial was to identify the changes in Bone Mineral Density (BMD) in relation to age and to identify how BMD varies from site to site. Sixty male Sprague-Dawley rats were split into six groups to allow measurements at one, two, three, four, five and six months of age (n=10 per group). At each time point a group of rats was scanned using a QDR4000 DEXA machine from Hologic. Duplicate BMD measurements were obtained for the whole body, spine and both femurs in vivo. The rats were then euthanased and the spine and both femurs were excised for ex vivo DEXA scanning and ashed calcium analysis. BMD increased almost linearly to four months and then formed a plateau. This indicates that from weaning to four months is an especially sensitive time for manipulating bone growth in male rats. There was a significant difference in BMD between groups (P<0.001), which is to be expected in growing rats. There was also a significant difference in BMD within groups (p