What does a veterinarian look for in performing a necropsy? Number one is to determine if the cause of death represents an increased risk for herd mates. If it does, how can we avoid the cattle disease in herd mates, and what’s the best treatment for those that do become ill.
A successful necropsy starts with a system. I begin by removing the entire respiratory tract – from the mouth back to the diaphragm. We can get a lot of information by looking at the laryngeal cartilages (our “voicebox”) for damage that could indicate diphtheria.
The trachea is the site where the cattle disease infectious bovine rhinotracheitis (IBR) lesions are found; there you’ll also find signs if the animal had tracheal edema (a honker).
The lungs can have an appearance associated with acute interstitial pneumonia, as well as different bacterial pneumonias, which we also know as shipping fever. The lungs’ appearance also can allow us to estimate the duration of the pneumonia. However, to nail down the exact cause of shipping fever, laboratory analysis of samples is necessary.
Other key pieces of bovine anatomy also come out with the lungs. I examine the heart for signs of hardware disease (e.g., an ingested piece of wire that penetrated the reticulum and then the outside covering of the heart). Sometimes, disease can cause a heart chamber to enlarge, or a heart valve to become infected and cease to function properly. In addition, a direct lesion in the muscle of the heart can result from one of various bacteria that cause pneumonia.
I then continue toward the back of the animal to examine the liver for flukes, abscesses, or signs of clostridial disease. The liver can also support a diagnosis of congestive heart failure, or a hepatotoxin (toxin affecting the liver). It’s also a good place to test for levels of some vitamins and minerals.
Meanwhile, the rumen contents also can suggest frothy bloat; even acidosis has a characteristic appearance of the fluid in the rumen. Free-gas bloat is typically suggested by a group of lesions, including pale hindquarters with edema between the muscle groups, and a congested neck.
Other organs, such as the spleen, offer clues. If the animal is anemic, icteric (yellowish-colored from the breakdown of red blood cells in the liver), and the spleen is enlarged, then anaplasmosis is a likely diagnosis. But, if the spleen is enlarged and has a strawberry-jam consistency inside, and the blood isn’t clotting, we may be dealing with anthrax.
A ruminant’s digestive tract is always a concern. The inner lining of the abomasum (the stomach chamber similar to humans) can signal a heavy worm infestation, or the potential of bovine viral diarrhea (BVD) due to ulcers. BVD signs also can be present in the esophagus and the small intestine. We also find an occasional ulcer that resulted in hemorrhage.
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Examination of the abdominal cavity might indicate an infection (peritonitis), or free fluid that would support a diagnosis of congestive heart failure. We can also find diseases of the kidneys, intestines which have twisted, and abnormal intestinal contents indicative of salmonella, overeating disease in a calf, or coccidiosis.
We can also examine the brain, bladder, joints, lymph nodes, udder and reproductive tract. And don’t forget that the best odds for diagnosing the cause of abortion come with providing your veterinarian both the freshly aborted fetus and the placenta.
This is a sampling of the information a necropsy can provide. Much of the ability to spot something abnormal or a cattle disease comes from seeing a few hundred normal examples, and your veterinarian can perform a necropsy to help you plan to avoid additional necropsies in the future. We don’t always deliver a definitive diagnosis from a necropsy and laboratory work, but many cattle diseases can be ruled out, and it becomes a baseline for potential future cases.
Mike Apley, DVM, Ph.D., is a professor in clinical sciences at Kansas State University in Manhattan.
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