Diagnostic survey of analytical methods used to determine bone mineralization in pigs.

ABSTRACT

Pigs from 64 commercial sites across 14 production systems in the Midwest United States were evaluated for baseline biological measurements used to determine bone mineralization. There were three pigs selected from each commercial site representing 1) a clinically normal pig (healthy), 2) a pig with evidence of clinical lameness (lame), and 3) a pig from a hospital pen that was assumed to have recent low feed intake (unhealthy). Pigs ranged in age from nursery to market weight, with the three pigs sampled from each site representing the same age or phase of production. Blood, urine, metacarpal, fibula, 2nd rib, and 10th rib were collected and analyzed. Each bone was measured for density and ash (defatted and non-defatted technique). A bone × pig type interaction (P < 0.001) was observed for defatted and non-defatted bone ash and density. For defatted bone ash, there were no differences among pig types for the fibulas, 2nd rib, and 10th rib (P > 0.10), but metacarpals from healthy pigs had greater (P < 0.05) percentage bone ash compared to unhealthy pigs, with the lame pigs intermediate. For non-defatted bone ash, there were no differences among pig types for metacarpals and fibulas (P > 0.10), but unhealthy pigs had greater (P < 0.05) non-defatted percentage bone ash for 2nd and 10th ribs compared to healthy pigs, with lame pigs intermediate. Healthy and lame pigs had greater (P < 0.05) bone density than unhealthy pigs for metacarpals and fibulas, with no difference observed for ribs (P > 0.10). Healthy pigs had greater (P < 0.05) serum Ca and 25(OH)D3 compared to unhealthy pigs, with lame pigs intermediate. Healthy pigs had greater (P < 0.05) serum P compared to unhealthy and lame pigs, with no differences between the unhealthy and lame pigs. Unhealthy pigs excreted significantly more (P < 0.05) P and creatinine in the urine compared to healthy pigs with lame pigs intermediate. In summary, there are differences in serum Ca, P, and vitamin D among healthy, lame, and unhealthy pigs. Differences in bone mineralization among pig types varied depending on the analytical procedure and bone, with a considerable range in values within pig type across the 14 production systems sampled.

There is little literature or data comparing bone diagnostic results for healthy, lame, and unhealthy pigs. Typically, diagnosticians assessing clinical lameness cases in pigs will measure bone mineralization along with histopathological evaluation to diagnose and assess the severity of metabolic bone disease. Bone ash is the primary method to determine bone mineralization, with the removal of the lipid in the bone (defatting) before the bone is ashed, compared to not removing the lipid before the ashing (non-defatted). Defatting the bone reduces the amount of variation across the bones compared to non-defatting. In this diagnostic survey, there was no difference among the healthy, lame, or unhealthy pigs when comparing defatted bone ash, however, unhealthy pigs had an increased bone ash percentage compared to the healthy and lame pigs when the bones were assessed using the non-defatted procedure. There was variation across production systems and pig types for serum vitamin D. When comparing the pig types, healthy pigs had increased serum Ca, P, and vitamin D [25(OH)D3] compared to the unhealthy pigs, with the lame pigs intermediate.