Lead poisoning is a serious condition which occurs when lead (a highly toxic metal) builds up in the cow's body. It often causes peripheral nerve damage in cattle, resulting in muscular weakness and roaring, which results from paralysis of the recurrent laryngeal nerve. It presents in cattle as acute and chronic poisoning, with the later being most common. Clinical signs of lead poisoning vary depending on the form of intoxication.
Prior to knowledge of its toxicity (before 1977 in the United States), lead use to be used in a wide range of products including most paint, shotgun pellets, car batteries, pipes, and roofing materials.
Most chronic lead poisoning cases in cows occur due to contamination of the environment or from exposure to lead paint used in the construction of older buildings in the United States. Environmental contamination occurs from cattle living in or near a lead-contaminated environment, such as within proximity to a battery factory, mines, smelters, or other industrial operations which use lead. This can also occur in the backyards of hoarders of junk outside or near car junk yards. Lead can also leach into the soil where it remains and further contaminates growing vegetation such as pasture grasses. When cattle graze on contaminated vegetation they can accumulate enough lead to produce clinical signs of lead poisoning. Paint-associated poisonings usually occur from cattle chewing on the wood of painted structures or from environmental contamination due to recent removal of the paint from the structure, through the use of paint removal tools such as sand blasting and power washing.