There are a multitude of toxins, such as heavy metals and other substances that cattle can come in contact with. Even with ever-increasing education, lead poisoning is still the number one toxic cause of death we, as veterinarians, see in cattle producing areas — especially in calves. Perhaps a reminder about the hazards will result in fewer deaths from lead exposure. Most cases are highly preventable and most occur on pastures or in feedlots.
Years ago lead-based paints were commonly used and of course there was leaded gas and a lot of that lead would end up in the used oil. These two sources have pretty much been eliminated but the burning of old buildings will still concentrate the lead in the ashes so proper disposal of the ashes and debris from the burning is critical.
Batteries are leading hazard
Acute lead poisoning is almost always the result of the accidental consumption of high concentrations of lead. The number one source is consumption of the lead plates in broken-down vehicle batteries. The lead pieces and fragments congregate in the reticulum (first stomach). From here the lead is absorbed into the bloodstream and causes the very dramatic signs we see as veterinarians.
Since the brain is affected by lead poisoning, many symptoms relate to the central nervous system. Convulsive fits, head pressing, hyperactivity or manic behaviour and blindness (which has always been permanent in the cases I have dealt with) followed by death in most cases. Veterinarians must rule out other nervous system causes of disease. In the case of poisoning from batteries most times there is more than one animal involved and commonly it is younger ones, as they are inquisitive.
If found alive and down in a convulsive fit they are often euthanized and a post mortem done. The key here is to confirm the diagnosis, find the source of lead so further cases don’t develop and treat those animals that are treatable. Safeguards need to be put in place so further cases in the future don’t develop.
To confirm the diagnosis your veterinarian may do several things. An autopsy may reveal lead pieces in the reticulum and kidneys that can be sent away to confirm a high lead level. Blood can also be checked on live animals.
If we suspect lead poisoning, it is key to find the source of lead and remove it so more cattle are not affected. This may mean walking and scouring pastures for discarded batteries or other sources of lead.
In treating live animals, veterinarians may use measures such as sedatives for hyper animals and giving Calcium EDTA to tie up the lead. In my experience a few cattle do make it but often remain a permanently blind animal. Then the issue of slaughter withdrawal times comes into question. Because of some heavy losses from lead poisoning in Alberta feedlots this was studied extensively by government toxicologists.
There are known acceptable levels in meat and the half-life of lead has been calculated to be right around two months. Withdrawal happens in steps. This means it takes two months to excrete one half the lead and another two months to eliminate another half of that half and so on. Depending on the amount consumed, the safe withdrawal time for meat consumption can be determined.
The lead goes into liver, kidneys and bone so depending on amount of intake euthanasia may be considered. Big pieces of lead stay in the rumen and are absorbed continually, which is another reason for euthanasia.
Prevention is the absolute key. We ideally don’t want to ever have to treat poisoning in the first place, it is not a pretty death and even if animals are found alive our treatment success will be poor. Add to this the fact that saved cattle are often blind and they need to kept a long time before meat is fit for consumption.
In order to minimize most encounters between cattle and lead batteries try and keep the following points in mind.
- Have a recycling policy and temporary storage area for old batteries: in other words don’t have a huge pile of batteries sitting where cattle can gain access.
- If you use electric battery fencers, remove the batteries in the fall or have them enclosed where grazing cattle can’t reach.
- Check any new pastures thoroughly for old yardsites, junk piles or deserted vehicles where batteries may be found.
- When changing batteries in vehicles, immediately remove the old one to your storage site. Any changing of batteries should occur in a shop or the old battery immediately stored away safely.
- Old batteries over time crack and break downfrom the freezing/thawing process, exposing the internal plates.
There have been a few catastrophic incidences of lead poisoning. In one situation, many cases of lead poisoning and death occurred at a feedlot where evidence suggests a large implement battery was mistakenly ground up through a feed-mixer and fed to the cattle.
It is alarming how many cattle can be killed by one vehicle battery. What started as a very innocent mistake had disastrous consequences for the feedlot. Lead was also used in older vehicles as filler for the bodywork so it is another source of lead. The battery though contains a huge amount of lead. With the chemical reaction in the battery the plates are salty, so it taste good to cattle.
Other sources of lead poisoning
Other oddball cases of lead poisoning have occurred where oil patch materials were left in a junk pile. Lead shot and the wad used in skeet shooting are also sources of lead. Dispatching animals for butchering with lead bullets can result in meat contamination. The precisely placed head shot with the proper caliber bullet by skilled marksmen is the proper way to butcher to avoid this issue. Studies done on hunting submissions have at times found high lead levels in the meat of game animals.
Pass the word about the danger of lead in batteries; be on the lookout for discarded batteries in and around yardsites. You may inadvertently find other sources of poisons such as bags of urea or soil sterilant sprays, all of which could have toxic effects to all animals including wildlife. Lets keep the environment cleaner, recycle those used batteries and try and minimize any chance of lead poisoning in our cattle. If you see other yardsites where batteries are in the open, suggest the producers recycle them. I still hear of cases as I travel the countryside.