Necropsies help diagnosis health, nutrition problems

If an animal’s cause of death is unknown, it pays to have your vet perform a necropsy (if you find the animal soon enough) to try to determine what happened, especially if a change in management could eliminate further deaths.

Heather Smith Thomas

December 7, 2010

8 Min Read
Necropsies help diagnosis health, nutrition problems

If an animal’s cause of death is unknown, it pays to have your vet perform a necropsy (if you find the animal soon enough) to try to determine what happened, especially if a change in management could eliminate further deaths. A postmortem exam might determine whether the animal died from hardware, pneumonia, poisoning or some other preventable problem.

W. Mark Hilton, DVM, associate professor of beef production medicine, Purdue University, tells producers their dead calf is worth nothing, but a dead calf with a diagnosis can be the most valuable animal on the farm.

“I feel good when I open a two-month-old calf and find he ate twine and got plugged up,” Hilton says. “The owner may be initially disappointed because he spent money for a necropsy, but it’s a relief to find out it’s not a herd-wide problem or a tip-of-the-iceberg situation.”

David Steffen, DVM, University of Nebraska-Lincoln (UNL) Veterinary Diagnostic Center, is a firm believer in accurate recording of mortality.

“For large operations, it helps to have a veterinarian teach the basics of postmortem examination to the herdsman so deaths can be classified as respiratory, enteric, nutrition or something else. Many feedlots do this. An accurate accounting can flag problems and signal a need for review of health programs. The necropsy serves as quality control for clinical assessments and treatment protocols,” he says.

Robert Glock, a University of Arizona diagnostic pathologist, says necropsies are wonderful training tools. “This is very important in feedlots. A necropsy can get the cowboys’ attention, going through the process and pointing out what happened and what might have prevented it,” he says.

From the experience, workers learn if pulling an animal for treatment sooner might have made a difference. In an extensive cow-calf operation, it might encourage the producer to utilize a herd health consultant on management plans.

“To me, necropsies for the purpose of just discovering what happened aren’t generally as important as a necropsy that helps identify a problem or provides useful information to the herd manager. It may not only be an educational experience for the herd manager and employees, but can help the veterinarian understand what’s going on and provide the platform for good communication among everyone,” Glock says.

For instance, Glock says, a common occurrence in cow-calf operations is an increase in calf deaths as calving season progresses. Part of the problem is contamination of the calving area, in which later calves are exposed to more pathogens from older scouring calves.

“Getting some laboratory backup to understand what is happening can help the producer fine-tune his cow management, including vaccination and altering the calving situation to reduce contamination. Some pastures may be so contaminated with clostridial diseases that you need to locate the calving somewhere else. To me, these are the benefits of necropsies,” he says.

Records are important
Steffen says that if animals are dying, the producer should keep good records. There’s a certain threshold for different production phases, for anticipated death loss. No matter how well a cow-calf operation is managed, there will be a certain number of calves lost to scours or odd situations (hairball, calf stepped on by the cow, etc.). If the number lost begins to exceed “average,” it’s time to take a closer look.

“Your veterinarian or an animal scientist can help you develop benchmarks for your operation and situation,” Steffen says. “If you have records, look at losses in previous years and set a goal for improvement – or try to maintain that low level.”

The producer needs to know whether it’s a situation that can be dealt with to prevent further losses, such as moving cattle out of a pasture that contains poison plants.

“In baby calves, if you have death losses from enteric diseases, there’s probably a certain level you deal with every spring. But, if suddenly you lose a couple of calves with neurologic signs, you might check them because you don’t expect it in this age group. It might be lead poisoning or rabies, or something else you need to know about,” Steffen says.

“An experienced producer usually has a fairly good idea of causes, due to symptoms, and what category to put the death loss into, but it’s still helpful to have a veterinarian open the calf to make sure you have the proper diagnosis. Some calves with enteric disease can show neurologic signs if electrolyte imbalances are severe or they become septic and get meningitis,” explains Steffen.

He adds that a feedlot animal with acidosis might have an increased respiratory rate, which can be mistaken for respiratory disease. And, gut blockage and bloat in a calf may be due to a hairball, eating dirt, an enteric disease in which the gut shuts down, or accidental torsion. A necropsy may let you know that it was a one-time thing.

Establish thresholds

“There’s always some regret when someone loses their fifth cow and wants to know what’s going on,” Steffen says. “We ask what they found with the first four and they say they didn’t examine those. They’ve lost that window of opportunity to have a better idea of what might be happening.”

He recommends producers confer with their local veterinarian to establish action thresholds; abortions are a good example. “You expect a certain number of animals in late gestation to slip their calves for whatever reason, but at some point you should become concerned – if the number increases above average (more than 1 or 2%),” Steffen says.

“When a 150-head cowherd starts calving March 1 and the owner tells me on Feb. 20 he just had his second cow abort, I generally tell him not to get too worried yet,” Hilton says. “If he has another one, that’s when I get involved to determine what’s going on. Other veterinarians may want you to call sooner, but I don’t usually send tissues to the lab until we have more than 2% abortions.

“Often, we veterinarians are reluctant to spend clients’ money, but considering the amount of money a stockman has invested in his operation, spending $100 or so for a necropsy to try to prevent future losses isn’t unreasonable. It’s a good investment in the overall business of the farm,” Hilton says. 

Heather Smith Thomas is a Salmon, ID-based rancher and freelance writer.

Communication is key

Robert Glock, a University of Arizona diagnostic pathologist, says it helps if your vet can communicate with the lab and determine which tissues would be best to send, based on evaluation of what’s happening in the field.

“We’re developing advanced technology, including different kinds of polymerase chain reaction (PCR) tests, some of which are quantitative. Not every lab will want the same specimen. It will depend on what tests they’re capable of doing. It helps to have good communication so that the most efficient set of specimens goes to the laboratory,” he says.

It may also help to send images (even by cell phone) to the veterinarian. A producer may find an animal too far out in the field for the vet to come immediately and could send images to the veterinarian.

Tips for preserving tissues

In a range situation, a necropsy by one of the cowboys can produce valuable information, even just by extracting the lungs so they can be preserved for inspection by the veterinarian, says Robert Glock, a University of Arizona diagnostic pathologist.

“It’s not always convenient for a veterinarian to rush out to the range, but if the cowboy can get the lungs, to refrigerate or haul to the clinic, this may be helpful,” he explains.

“One of the challenges of necropsies is preservation. Refrigeration works well. If you can chill tissues quickly, with refrigeration or wet ice, then package them for shipping with ice after they’re chilled, this works best,” he says. “If you send tissues with ice packs before they’ve been chilled, you end up with rotten material. It’s important for specimens to get there with maximum benefit.”

If it’s late in the day, Glock advises refrigerating tissues overnight and shipping the next day. “That’s better than trying to get them to the lab a day sooner without being properly refrigerated first. You’re better off if they’re chilled and three days old than poorly chilled and two days old,” he says.

Nutritional issues

“It’s not unusual to see (death) cases with a nutritional component. A necropsy gives opportunity to explore this. It may not be easy to define with a single necropsy, but there may be some history that suggests it’s worthwhile to evaluate nutritional status,” says Robert Glock, a University of Arizona diagnostic pathologist.

“I spent 10 years at the diagnostic lab in Colorado, and we saw copper deficiency. Often, people aren’t thinking about that, but a necropsy situation can suggest that the herd needs to be evaluated for copper deficiency. Here in Arizona, we have areas with severe selenium/vitamin E deficiency.”

He says a necropsy may suggest a need to supplement cattle with selenium and/or vitamin E. “People usually don’t listen to these suggestions until an animal dies. This provides an opportunity to demonstrate the problem, and the lesson sinks home,” he says.

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