Total body and regional measurements of bone mineral content and bone mineral density in pigs by dual energy X-ray absorptiometry

Dual energy X-ray absorptiometry (DXA) was used to make total body and regional measurements of bone mineral content, bone mineral density, and bone area during the growth of pigs from 3 to 138 kg. In all, 1,053 total body scans were performed on 587 live pigs. Regional measurements consisted of the front legs, trunk, and back legs. In addition, bone mineral density readings were recorded for the head, pelvis, spine, and ribs. From about 5 to 75 kg, a greater percentage of the total body bone mineral content (BMC) was located in the trunk region. However, the percentage of BMC in the front and back legs continued to increase linearly whereas the percentage of BMC in the trunk region peaked at about 25 kg and then decreased logarithmically. Allometric analysis revealed that up to about 30 kg the BMC increased more rapidly in the trunk region compared to the front or back leg regions (P > 0.05), but after 30 kg the increase in BMC was more rapid in the leg regions (P < 0.05). Overall, the rate of increase in BMC in the back legs was slightly more than in the front legs (P > 0.05). Positive allometric growth of BMC was observed when compared with the increase in bone area for the same region. By far, the highest measured level of bone mineral density (BMD) was in the head region (P < 0.05), followed in order by the front legs, spine, back legs, pelvis, and ribs. Over the entire range of growth from 3 to 138 kg, the highest relative growth coefficient for the increase in BMD occurred in the pelvic and back leg regions and the lowest was in the ribs (P < 0.05). For pigs < 30 kg, the highest growth coefficient for BMD relative to BW was in the spine (P > 0.05). The growth coefficients for BMD in the back legs and total body increased in pigs greater than or equal to 30 kg and those of the front legs and trunk regions decreased.