By Barry Whitworth, DVM

Lead is one of the most common causes of poisoning in cattle. Most clinical signs of lead poisoning are usually associated with the nervous system and the gastrointestinal tract.
The most common sources of lead are improper disposal of car and farm machinery batteries and used motor oil. Other sources include old structures with lead paint, linoleum, lead pipes, and grease from machinery. Since calves are more curious and prone to nibble or lick objects, poisoning is seen more frequently in calves than older cattle.

Most animals have a background level of lead. Toxicity occurs when the background level plus the amount ingested reaches a toxic level. Doses of 50 to 400 mg/kg may kill a calf. Higher doses (600 to 800 mg/kg) are required to kill adult cattle. Cattle that consume 7 mg/kg a day will eventually die from lead toxicity.

Clinical signs of lead toxicity appear acutely. Many times, producers just find dead animals. Most clinical signs observed are associated with the neurological system. One common sign is blindness. Producers may find a calf walking aimlessly or walking into objects.
Other signs are circling, head pressing, ataxia, muscle tremors, and convulsions. Occasionally, gastrointestinal system signs such as colic, anorexia, diarrhea, grinding of teeth, and frothing of the mouth precede the nervous signs.

Clinical signs of lead poisoning are similar to other nervous and gastrointestinal diseases. Some diseases that can be confused with lead poisoning are polioencephalomalacia, nervous coccidiosis, tetanus, rabies, and listeriosis.

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