Cause:
Insufficient copper in the diet (primary copper deficiency), or dietary constituents that prevent dietary copper from being absorbed from the digestive tract (secondary copper deficiency). Secondary copper deficiency associated with high sulfur levels in the drinking water, has been reported in bison in Saskatchewan (65).
Clinical signs:
Clinical signs of copper deficiency in bison include stiff gait, lameness leading to recumbency, emaciation, diarrhea, and loss of coat color (65).
Diagnosis:
The clinical signs of emaciation, lameness, and diarrhea combined with loss of hair coat color would be suggestive of copper deficiency. Normal serum and liver copper levels have not been established for bison. In the reported cases of copper deficiency in bison, serum copper levels were 5.8 mol/l and liver copper levels were 0.02 mol/g. Both of these levels would also be considered low for cattle (65).
Postmortem findings:
Postmortem findings were mainly associated with degenerative lesions of the joints, which included thinning of articular cartilage, defects in the articular cartilage and rupture of joint ligaments and capsules. There was as rupture of flexor and extensor tendons as well as fracture of the patellas (65).
Treatment:
Treatment protocols have not been reported for copper deficiency in bison. In advanced cases with degenerative joint lesions, such as those that have been reported, treatment would probably be unsuccessful. The diet of affected bison should be supplemented with copper. However, safe dietary levels of copper have not been established for bison. In cattle, copper sulfate can be added to the salt-mineral mix to a level of 3 to 5% of the total mineral mixture (19).
Control:
Feed, water, and pasture should be sampled to determine if there is adequate copper available in the diet. They should also be tested to see if there are any elements present, such as molybdenum, or sulfates, that may inhibit the absorption of copper from the diet.
In cattle, the minimum dietary requirement is 10mg of copper per kg of dry matter. Since the minimum dietary copper requirements for bison have not been established, it is not known whether these levels would be adequate. In cattle, over supplementation with copper can produce toxicities. Care should be taken when copper supplements are prescribed. A qualified nutritionist should be consulted to examine both feed and water analysis before supplementation of copper, or other trace minerals is recommended.