Cause:
Arthrogryposis is a birth defect. It is seen as a result of inbreeding.
Clinical signs:
Clinical signs of arthrogryposis in bison include exaggerated slope of the back, increased angulation of the hock, stilted gait, poor muscling of the hind quarters, poor weight gains and reduced growth potential. Bison with arthrogryposis stand with their hocks abnormally close together or with their hocks crossed (66).
In both of the cases reported, the bison were affected from birth. One case resulted from a sibling mating (66).
Postmortem findings:
There will be reduced muscle mass of the carcass, especially of the hind quarters. The hock joints will be in extreme angulation, and will be rigidly fixed around the tibiotarsal joint. There may be thinning and erosion of the articular cartilage of the bones in the hock joint, especially the talus (66).
Diagnosis:
The clinical signs would be suggestive of the disease. Normal hematology, serum chemistry, and plasma trace minerals would help to rule out other causes of disease, since these values were within normal ranges for cattle, in the cases reported in bison (66). Radiographs of the hind limbs will be normal (66).
Analysis of the pedigree of affected bison may demonstrate that the disease has a familial trend. Since affected bison have reduced growth rates and are poor doers, the diagnosis may best be made by postmortem examination. Tissues submitted to a pathology laboratory for examination should include the bones and joints of the back legs.
Treatment:
Treatment of arthrogryposis in bison has not been reported. It is unlikely that advanced cases of arthrogryposis will respond to any treatment.
Control:
Control will involve pedigree analysis of affected animals, and elimination of breeding combinations that result in the production of arthrogrypotic calves. If cows or bulls can be identified as individuals that produce arthrogrypotic calves, they should be removed from the herd.