Osteoporosis in the Norwegian moose

Abstract

In the last decade, an increased frequency of fractures among wild moose in the southernmost parts of Norway has been reported. This study focuses on bone mass, mechanical strength, and metal levels in the metacarpal bone of moose hunted in Aust-Agder (AA) County in southern Norway compared with control areas (CA) in more eastern and northern parts. Metacarpal bone with soft tissue from 106 AA and 37 CA animals were excised after hunting. Bone mineral density (BMD) was measured using dual-energy X-ray absorptiometry (DXA) at the proximal joint (trabecular bone tissue) and 100 mm distally (cortical bone tissue). Both accuracy and reproducibility of the method in these large bones were tested. Biomechanical strength was carried out using a three point bending test in bones from nine AA and eight CA animals of the same age. Metal concentrations in bone tissue were determined by atomic absorption spectrophotometry (GF-AAS) and atomic emission spectrometry (ICP-AAS). BMD of the proximal region was 1.58 +/- 0.39 g/cm(2) (mean +/- SD) for AA, 1.88 +/- 0.58 g/cm(2) (p < 0.01) for CA, 2.08 +/- 0.36 g/cm(2) for distal AA, and 2.16 +/- 0.48 (not significant) for distal CA. In analysis of covariance (ANCOVA) tests with age and region as factors, together with weight as cofactor, there were significant effects on BMD in both the proximal and distal areas for all factors. The bending strength of metacarpal bone was 9378 +/- 1814 N and 16,707 +/- 3065 N (p < 0.01) in AA and CA animals, respectively. There was no differences in element content except for the concentration of lead, where the mean value for AA animals was 1.5 +/- 0.8 mg/kg and CA 0.4 +/- 0.3 mg/kg (p < 0.01). In conclusion, the animals from the southern part of Norway had lower bone mass, decreased mechanical strength, and an increased bone concentration of lead.