4 June 2008

3 minute read

North America

SDSU Extension Veterinarian Russ Daly said that of the cases of lead poisoning diagnosed over the past six years, 39 percent of them occurred in the month of June, with an additional 27 percent occurring during May.

“Lead poisoning is the most commonly diagnosed toxicity of cattle in cases submitted to the ADRDL. Cattle may encounter lead through exposure to man-made lead-containing materials that are sometimes present in trash piles in pastures or shelterbelts. May and June coincide with turnout onto pastures in South Dakota, and therefore the first encounters with these materials usually occur then.”

Common lead sources for cattle include deteriorating car batteries that have broken apart, which may be found in junk piles or along fence lines as past power for electric fences. Cattle, especially calves, will selectively lick on these and other sources of lead, Daly said.

Other sources are lead paint that may be found on discarded lumber (even after burning), discarded oil and grease from old machinery, lead ammunition, and many older building materials such as old pipes, solder, linoleum, and window putty.

Small amounts of lead, especially when consumed over time, can result in signs of lead poisoning. Lead has effects on both the nervous system and the digestive system, with signs of nervous system disturbance more common. Early signs include incoordination, lack of appetite, blindness, and muscle twitching. In many animals, convulsions and death will follow. Signs may even appear up to two weeks after cattle are removed from the source of lead, due to prolonged absorption from the digestive tract. Often, especially with younger calves, animals are found dead in the pasture with no prior signs. Lead poisoning is much more commonly found in calves — accounting for 88 percent of the cases from the ADRDL from fiscal years 2003-2008 — rather than adult cattle older than 12 months.

Daly said that since many other illnesses can cause similar clinical signs (for example, rabies or polio affecting the nervous system, or anthrax or blackleg causing sudden death on pasture), producers should ask a veterinarian to examine affected animals. Diagnosis of lead poisoning can be made by lab analysis of a blood sample, or kidney or liver from animals that have died.

Treatment of lead poisoning is often unrewarding, especially in advanced cases. Veterinarians may employ calcium EDTA or thiamine injections, or drenches with magnesium sulfate in attempts to remove the lead from the animal’s system.

“Cattle producers should take time to closely examine their pastures for any potential sources of lead. The obvious source is discarded batteries, which should be removed from the pasture, but non-obvious sources could be present in any junk or trash pile that cattle have access to,” Daly said. “Producers should assess these exposures and may wish to fence cattle out of those areas or remove the piles altogether. “

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