I was recently reminded of the challenges of dealing with herds that have been accidentally exposed to old batteries and other sources of lead.
A veterinary colleague told me about a lead toxicity case he was dealing with involving a large group of cattle.
In these cases, the immediate challenge for the producer and the veterinarian is to obtain a diagnosis and deal with the inevitable neurological cases and deaths.
However, the problem does not end there because lead exposure constitutes a food safety risk. Once a diagnosis has been made, the next challenge is determining which animals have been exposed and whether they will be able to enter the food chain safely.
Read Also
Dry summer conditions can lead to poor water quality for livestock
Drought conditions in the Prairies has led to an decrease in water quality, and producers are being advised to closely monitor water quality for their animals.
Dr. Barry Blakley, a toxicologist at the Western College of Veterinary Medicine in Saskatoon, says his toxicology lab receives samples from 50 to 60 lead poisoning cases in cattle herds a year.
He said most of these cases occur in May and August, which coincides with seeding and harvesting. They are busy times for farmers and also when cows are often turned out into new grazing areas.
Batteries are the most common source of lead poisoning.
Cattle can be exposed to them when they are not stored or disposed of properly or if cows are turned out into areas containing old farm machinery. Sometimes batteries have fallen into feed mixers and been accidentally distributed to large groups of cattle.
Cows are attracted to used batteries because of the salty taste. They’ll lick them, chew them and eat them whole. It takes just one battery to kill one or more animals and cause clinical signs of poisoning to appear in others.
However, some herd mates may have higher lead levels in their blood and not show any clinical signs. These asymptomatic animals pose a serious food safety issue that may go undetected.
Cows are more apt to lick or chew on discarded equipment than other animals. It’s just part of their nature.
As well, cows have a reticulum, a compartment-like structure in their stomach that acts as a trap for ingested foreign objects. Parts of a battery can be lodged in the reticulum, where they slowly dissolve instead of passing through the cow’s body.
One or more sudden deaths in a herd could indicate lead poisoning.
Clinical signs include blindness, convulsions, depression or hyperactivity. Lead salts irritating the cow’s stomach lining may also cause an inactive rumen.
Your veterinarian can help confirm lead toxicity by doing a post-mortem on suspicious cases and sending the liver and kidney to the toxicology laboratory for lead analysis.
Blood samples can also be analyzed for lead levels in living animals that have been exposed.
Lead poisoning can appear clinically similar to other diseases that also cause neurological signs, such as polioencephalomalacia, rabies and other toxicities.
It is important to ensure that dead animals are disposed of properly so that species such as eagles do not suffer from lead toxicity after feeding on carcasses.
Prevention is not complex. It just involves making sure cattle aren’t exposed to batteries or other lead sources such as crankcase oil and old lead based paint, tarpaper and shingles.
Blakley recommends the following strategies:
• find the nearest depot that accepts used batteries and follow proper disposal methods;
• don’t bury used batteries because the soil will eventually erode and expose them. As well, lead seepage can potentially contaminate soil and water;
• don’t allow cattle to graze in areas containing machinery or abandoned buildings. Ensure that pastures are clear of junk before putting cows out to graze.
Lead poisoning in cattle herds causes economic loss, animal suffering and food safety concerns and can be a major blow to a producer’s breeding program.
It can easily be avoided with a little care.
John Campbell is head of Large Animal Clinical Sciences at the University of Saskatchewan’s Western College of Veterinary Medicine.
