Volume VIII Number 6 November/December 2000

Necropsy Can Provide Vital Information for the Future of Herd Health

by Jill J. Dunkel



Determining the cause of death of an animal can be vital to maintaining the health of one's herd. "Knowing why an animal died allows producers and veterinarians to target therapy for future problems," says Dr. Mac Devin, technical services veterinarian for Fort Dodge Animal Health.

"If you lose an animal, especially more than one, you need someone skilled in diagnostics, and that person is your veterinarian," he says. "By analyzing the information, an individual and his veterinarian can make choices on the best management solutions."

Many things can be learned by gross necropsy, or studying the animal and it's organs and tissues with the naked eye. Initially, the veterinarian looks for any external signs of trauma, such as blood on the skin or burned places along the coronary band or the bottoms of the feet. Burns could indicate the animal was struck by lightening.

Once the body cavity is open, the veterinarian can learn a variety of clues from the animal's internal tissue.

  • Fat discoloration: The fat should be pale yellow.
  • Joint Fluid: It should be straw colored and a sticky consistency.
  • Large Blood Clots: Large clots indicate trauma to the body, possibly in the form of a gunshot.
  • Blood sequestered to the front of the body: This could indicate bloat. Increased pressure in the abdomen and chest area retards blood flow to the back part of the animal. The tissue in the back part of the animal would be pale, while much of the animal's blood becomes trapped in front of the shoulders.
  • Accumulation of gas under the skin: Gas accumulation can result several hours after the animal dies, therefore it is important to conduct a post mortem examination as soon as possible after the death of the animal. However, gas accumulation is also a symptom of blackleg.
  • The color of muscle tissue: Very dark, almost black, muscle tissue is another symptom of blackleg. Clostridial organisms live in the ground. With the extreme dry conditions, animals graze close to the ground and can pick up the clostridial spores, cautions Dr. Devin.
  • Diffuse swollen areas: Swollen areas are potentially a symptom of snake bite. Note if there is an abscess in the area due to the snake's dirty mouth.

The next step is opening the oral cavity, neck and chest to expose the respiratory tract. Look for abnormalities such as:

  • Ulcers on the tongue, oral and nasal cavities and trachea: IBR is a highly infectious disease that can leave such ulcers. IBR travels through a herd very fast, and it is important to vaccinate for the disease to prevent widespread illness.
  • Ulcers or dark spots on the esophagus: These ulcers can indicate Bovine Viral Diarrhea.
  • Swelling or edema in the esophagus or trachea.
  • Condition and color of the lung: The lung should be light pink. A diseased lung is meaty, heavy and wet. An animal suffering from chronic pneumonia will have lungs similar in color to the liver, usually beginning in the lower and/or front part of the lung tissue. According to Devin, a good way to test the condition of the lung is to put the lung in water. If it floats, it is a normal lung; if it sinks, it is abnormal.

After opening the lung, the vet will look at the condition of the tissue. Lung worms leave the lung bright red and irritated. The worms may even be observed in the airways. Lung worms most often occur in the winter or spring, and the animal may show symptoms of pneumonia, such as coughing.

  • The heart muscle: Lesions in the heart wall may indicate a secondary haemophilus infection. A normal heart is thick on the left side -- the side that pumps blood throughout the body. A fibrin-filled pericardial sack -- the sack surrounding the heart -- is a symptom of a hardware cow.
  • Abnormalities of the liver: Look for flukes in the bile ducts. Black streaks in the liver tissue indicates deer flukes.

Analysis of the digestive tract can also be helpful. If toxic plants are suspected, the vet will collect samples from the rumen and other parts of the digestive tract to be analyzed in the lab.

Thickening of the digestive tract: This could indicate Johne's Disease. Johne's Disease is spread vertically, from the mother's feces to the calf as he nurses. Cattle infected with the disease will suffer from chronic diarrhea and ultimately will waste away. According to Devin, Johne's Disease is moving to the forefront of the animal health industry as a significant threat to cattle.

Due to the possibility of fatal pathogens, such as anthrax and rabies, or other diseases, such as tuberculosis, being passed on to humans with direct contact of these tissues, conducting a necropsy should be left up to a veterinarian, Devin suggests.

In addition to gross necropsy, tissue samples can be examined under the microscope. Bacteria can be identified, and tissue sensitivity tests can be run to determine future therapies.

"Once we have a targeted idea of what antibiotic the bacteria is sensitive to, a choice can be made on the best management approach. In a pasture situation, an injection with a three-day therapy is preferred, where as cattle in a hospital pen could be doctored every day," Devin explains.

Through a combination of gross and tissue necropsy, plus providing a veterinarian with a thorough history of the animal, cause of death and prevention measures can likely be determined.
 








  

   
   

   


   

   		
  
   



  

    



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