Editor’s note: Though calves are typically born in the spring, fall-calving herds need to also be aware of lead poisoning in cow-calf herds
Spring is a wonderful time of year with everything coming out of winter hibernation and the world seeming to come to life again. It is also the time when most farmers and ranchers calve, and it is when we see increased numbers of lead poisoning cases. The typical case is one where multiple calves less than 3 to 4 months old die, but the cow herd remains normal.
Often the calves are simply found dead and have no postmortem lesions, or all that is found at necropsy are congested intestines and red lungs. It seems that the younger the calf the faster they die. Because the calves are not seen displaying signs of central nervous system (CNS) disease, it is easy to misdiagnose the cause of death as something like enterotoxemia, or acute pneumonia and not give lead toxicity a thought. Often the only hint that lead might be the problem is that multiple calves have died and there is no obvious cause.
Many calves likely display CNS signs before dying, but they are unseen by the owner. A case this last spring is typical. Eleven 4–8 week-old calves died within three weeks. The first few were found dead, but the owner began watching the group more closely and noticed CNS signs, such as circling, ataxia, falling over and thrashing about, and nystagmus in several calves that subsequently died. All calves with CNS signs were dead within 12 hours and sometimes less than 1 hour of the first sighting of CNS signs.
The source of the lead was felt to be an electric fence battery that had been tipped over in the pasture spilling lead-containing acid. Lead should be kept in mind as a differential diagnosis for sudden or unexplained deaths of young calves for which nothing else is obvious. Even if the owner is positive that there is no source of exposure, do not be too quick to rule out lead. In any case of accidental poisoning, if the owner thought that there was something in the environment that could kill their calves, they would have removed it.
The two best samples for diagnosis of acute lead toxicity are whole blood and kidney.
A more complete discussion of this subject is in the Summer 2005 Kansas Veterinary Quarterly. Visit http://tiny url.com/5r6nf32 and click on “Summer 2005”.
This information from Jerome Nietfeld, DVM, PhD, Kansas State University Veterinary Diagnostic Laboratory, was reprinted with permission from the Kansas Veterinary Quarterly, Spring 2011.