MORE ON LITHIUM TOXICITY IN CATTLE
More information has surfaced on the toxicity of lithium
in cattle following my comments on lithium grease in an
earlier FORUM.
A study on the toxicity of lithium in cattle was reported
in 1980 (Johnson,et a1.. Vet. Hum. Toxicol. 22:248, 1980).
They reported accidental exposure of beef cattle to "tacky
lithium grease", 5% lithium in oil (viscosity 90), in
which 18 cattle became sick or died. Clinical signs were
severe depression, diarrhea and ataxia. Serum contained
0.49 ppm of lithium, and ingesta had 4.6 ppm. Since these
levels were so low, they believed that other contam'i-nants
in the grease may have caused or enhanced the toxic effect
of lithium.
In their subsequent study they exposed eighteen mixed-breed
beef cattle up to 700 mg/kg body weight of lithium chloride
as a single oral dose. Signs were mild and transient in
the 250 mg/kg group. Doses of 500 and 700 mg/kg were toxic
and fatal. Signs were salivation, depression, anorexia,
hypodip-sia,anuria, and diarrhea, with the high-dose group
having severe depression and ataxia. Lesions included a
dose-related gastroenteritis, slight interstitial nephritis,
and hepatic fibrosis. The concentration of lithium in serum
was 54 ppm, while tissue residues of lithium were: liver-68.7ppm,
kid-ney-67.1ppm, and brain-51.8 ppm.
Based on their study, my conclusion is that a 1000 pound
bovine must consume about 2.5 kg of grease containing the
equivalent of 5%lithium chloride (or about 0.5 kg
[1.1 pounds] of grease containing 5% lithium) to
produce clinical signs, and about twice that to cause death.
If there is an enhancement of toxicity due to the non-lithium
portions of the grease, then a smaller dose of grease would
be required to elicit a toxicosis.
F. R. Robinson, DVM, PhD Veterinary Toxicologist
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