Severity and distribution of ventral thoracolumbar spondylosis and histological assessment of associated intervertebral disc degeneration in cull rams

Abstract

AIM: To conduct a pilot study investigating the incidence and pathology of spondylosis in a sample of cull rams in New Zealand.

METHODS: Vertebral columns from 51 cull rams from different properties were assessed radiographically for evidence of spondylosis. They were graded according to severity, using a four-point grading system. Samples of intervertebral discs representing different grades of spondylosis were examined histopathologically.

RESULTS: Forty (78%) rams had spondylosis in at least one intervertebral space. Of these, 11 had ankylosis involving one or more intervertebral spaces. The frequency of spondylosis was greater in the thoracic than lumbar region (p<0.001), and was most frequent between T10–T11. Histopathological examination of intervertebral discs associated with all grades of spondylosis revealed degenerative changes in the annulus fibrosis.

CONCLUSIONS: Spondylosis appeared to be common in cull rams and affected thoracic and lumbar vertebrae. It often involved ankylosis of adjacent vertebrae, and was associated with degeneration of the intervertebral disc.

CLINICAL RELEVANCE: Spondylosis may reduce the serving ability of rams and be an important underlying reason for culling. The pathogenesis of spondylosis is unknown but may involve high mating frequencies during the breeding season.

KEY WORDS:

• Ovine
• ram
• vertebrae
• spondylosis
• ankylosis
• annulus fibrosis

Acknowledgements

The authors would like to thank Medallion Petfoods in Waipukurau for providing the vertebral columns for this study; and Mike Hogan, Pat Davey, Evelyn Lupton, Mary Gaddam and Linda Darragh for technical assistance. This work was funded by the Institute of Veterinary, Animal and Biomedical Sciences Postgraduate Research Fund.