Even with ever-increasing education, lead poisoning is still the No. 1 toxic cause of death we see as veterinarians in cattle-producing areas, especially on calves.
This article will review the disease, the common sources of lead for cattle, and the circumstances where they occur. Hopefully, this will result in fewer deaths from lead exposure, which in most cases are highly preventable.
Years ago, lead-based paints were commonly used and of course we had leaded gas, where 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 site is critical.
Acute lead poisoning is almost always the result of the accidental consumption of high concentrations of lead. The No. 1 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 symptoms we see as veterinarians: convulsive fits, head pressing, hyperactivity or manic behaviour and blindness (which has always been permanent in the cases I have treated) followed by death in most cases. Veterinarians must rule out other nervous causes of disease. In the case of 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, and 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 exposures don’t occur.
To confirm the diagnosis, your veterinarian may do several things. An autopsy may reveal lead pieces in the reticulum and a kidney can be sent away to confirm a high lead level. Blood can also be checked on live animals.
- More vet advice with Roy Lewis, Dvm: Preventing bloat when pasturing alfalfa
Finding the source of lead and removing it so more cattle are not affected may mean walking and scouring pastures for discarded batteries or other sources of lead. For live animals veterinarians may use such things as sedatives for hyper animals and giving calcium EDTA to tie up the lead. In my experience, some do make it, but often you are left with a blind animal.
Then the issue of slaughter withdrawal comes into question. Because of some recent 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.
This means it takes two months to excrete half the lead, two months the next half and so on. Depending on the amount consumed, the safe time for consumption can be determined. The lead goes into liver, kidneys and bone, so depending on intake, euthanasia may be considered. Big pieces of lead stay in the rumen and are absorbed continually, which is another cause for euthanasia.
Prevention of lead poisoning 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. Even if found alive, our success will be poor. Add to this the fact that saved cattle are often blind and we need to keep them a long time before they are fit for consumption.
So in order to minimize 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 new pastures thoroughly for old yard sites, junk piles, or deserted vehicles where batteries may be found. When changing batteries in vehicles immediately remove the old one to your storage site.
There have been a few catastrophic incidences of lead poisoning. 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. Any changing of batteries should occur in a shop or the old battery stored away safe immediately. Lead was also used in older vehicles as filler for the body work so it is another source of lead.
The battery though has a huge amount of lead in it and with the chemical reaction in the battery, the plates are salty-like so taste good to cattle. Old batteries crack and break from the freezing-thawing process over time so the internal plates are exposed.
Other oddball cases of lead poisoning were oilpatch-based stuff left in a junk pile. Overshooting of animals for butchering with lead bullets has resulted in meat contamination. The precisely placed head shot with the proper-calibre 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.
Pass the word about the danger of lead in batteries. Be on the lookout for discarded batteries in and around yard sites. You may inadvertently find other sources of poisons such as bags of urea, soil sterilants sprays all of which could have toxic effects to all animals including wildlife.
Let’s keep the environment cleaner, recycle those used batteries and try and minimize any chance of lead poisoning in our cattle. If you see other yard sites where batteries are in the open, suggest the producers recycle them. I have heard of a couple of cases already this summer and both were batteries.