More than 85 percent of lead poisoning incidents among cattle in Alberta result from accidental consumption of discarded materials from farm vehicles or machinery.
Used crankcase oil, discarded batteries, grease (which contains up to 50 percent lead), leaded gasoline and used engine oil filters are the most dangerous materials.
Drinking water contaminated from lead pipes or soldered tanks can cause poisoning, particularly in areas where the water is soft.
Junk piles in pastures are another common source.
Other sources include some crop sprays, putty, lead-based paints and painted surfaces, roofing materials, plumbing supplies, asphalt, lead shot, linoleum and oil field wastes.
Boiled linseed oil, which contains lead, may poison livestock when it is used as a laxative. Even a small amount of lead can kill cattle.
Cattle will drink crankcase oil, lick grease from machinery and chew on lead plumbing and batteries. The lead in these materials settles in the stomachs, where acids gradually change the lead into poisonous salts.
Lead causes anemia when it combines with red blood cells and bone marrow. It damages the small blood vessels, causing bleeding, and deprives the nerves, the brain and other organs of oxygen. It severely damages the kidney and liver and causes sterility, fetal death and abortion.
Lead poisoning is most common among calves because they are curious feeders, and both milk and milk substitutes increase the amount of lead absorbed by calves. Sucking animals can also receive lead in their milk.
Lead poisoning occurs when the diet, housing or environment of cattle is changed, like in the spring when animals are turned out to pasture, or in the fall when they are returned to the yard.
The cattle eat discarded materials that have accumulated in yards, barns or pastures since the areas were last occupied. In one case, 30 adult beef cattle died when a discarded tractor battery, left in a field, was accidentally chopped into corn silage.
There are many reports of cattle poisoned after eating soil on which used motor oil has been spilled.
Calves are susceptible to poisoning if they are crowded or kept in confined housing because of the abnormal feeding behaviors they may develop.
Cattle that eat lead will likely die. All animals with access to a source of lead are at risk.
When one or two animals in a herd die or show signs of poisoning, other animals in the herd may also be suffering. These animals might appear healthy, but might be growing poorly as a result of subclinical lead poisoning.
Although clinical signs of poisoning normally precede death, most animals are found down or dead on the pasture.
Clinical signs range from the subtle to the dramatic and take from two days to three weeks to develop.
The first sign is often depression, loss of appetite or occasionally diarrhea. Cattle may grind their teeth, bob their head, or twitch their eyes or ears. Some animals may circle, press their head or body against objects, or become unco-ordinated and stagger. Muscle tremors, excitement, mania, blindness or convulsions may also be seen.
Death usually results from respiratory failure during a convulsion, or is associated with misadventure such as drowning in a pond.
After the onset of signs, cattle with acute poisoning usually die within 12 to 24 hours.
In less acute cases, cattle may survive as long as four or five days.
If lead poisoning is suspected, have a veterinarian examine the affected animals to confirm the diagnosis. A correct diagnosis is extremely important for identifying the problem and preventing a recurrence of the disease.
Treatment is seldom effective because once clinical signs are seen it has usually progressed too far. Treatment is complicated, costly and requires several days of therapy. Therefore, it is usually reserved for valuable animals or for animals suspected, but not showing signs of lead poisoning.
Lead poisoning of cattle can be avoided if a farmer practises good waste management.
- Do not leave petroleum products lying around or stored in open containers. Place used motor oil in sealed containers.
- Keep trash out of pastures and other sites used by animals. Fence dump sites and bury trash. A single dump site is safer than several sites. Clean existing dumps.
- Dispose of used batteries without spilling their contents. Do not leave batteries in barns, pastures or the farmyard.
- Use lead-free paint on barns, fences or other structures in areas accessible to livestock. Keep paint cans closed and do not discard them in areas used by livestock.
- Do not park farm machinery in the barn or near areas used by livestock. Service farm machinery in areas that are completely separate from animals.
- Avoid holding animals in a yard. No matter how clean the yard is, it may be difficult to eliminate all toxic substances or to ensure that others take the same precautions.
- Inspect all areas carefully before introducing animals to a change of location.
- Be knowledgeable about lead poisoning and informed about the hazard it presents to livestock. Discuss waste management practices with neighbors and other producers to develop a community awareness of the hazards to cattle from lead.