Ankylosing Spondylitis of Holstein Bulls
Lisle W. George
Ankylosing spondylitis is an inflammatory disease of joint tissue associated with fusion of lumbar vertebrae in Holstein bulls. Approximately 4% of all Holstein bulls intended for artificial insemination are culled each year because of spondylitis.1 The clinical onset of the condition is insidious.
The first signs of the disorder are a stilted gait, reluctance to move, and dragging of the toes of the rear limbs. Affected bulls are slow to mount teaser dummies for collection. The condition is progressive, and over several months the animals develop paraparesis and ataxia. With mounting, the ankylosed area of the spine may fracture, leading to acute recumbency. Pathologic changes associated with the condition include calcification of the ventral vertebral ligaments between the T11 and L3 vertebrae. The condition appears to be hereditary. All bulls with the condition possess the class I major histocompatibility complex BoLA A8 phenotype. In comparison, the phenotypic frequency of BoLA A8 in the general population of normal Holstein bulls is only 44%.2
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