Tracking down cause of sudden death in cattle herds is vital

Dead animals are a sight no producer wishes to see. The sudden death in a previously thriving cattle herd can be devastating and frustrating.

But it’s important to have a close second look at the case and determine the cause of death, or to at least rule out certain possibilities to help with future prevention and management decisions.

The first step to investigating sudden death is to characterize facts of the situation — these details will narrow down potential causes.

Important questions should address several factors:

  • What age groups are affected?
  • What clinical signs occurred before death?
  • How many animals are affected?
  • What is the timeline of the deaths?

The second step is to carry out a clinical examination of the surviving herd and have autopsy examinations conducted on the deceased animals. There may be mild or subtle clinical disease in the living animals that could provide a clue to the diagnosis. The pattern of lesions discovered during an autopsy may point to a particular cause or quickly rule out others.

When an individual animal suddenly dies, it could be due to a number of reasons. With their complex stomach and intestines, cattle are prone to bloat and twisted guts, both of which may quickly kill an animal. Lightning strikes are always a possibility during the summer thunderstorm season. Rupture of major blood vessels can also lead to a sudden death.

On the other hand, herd outbreaks suggest more sinister causes. Lucky for us, the great cattle plagues of yore are no longer an issue. Vaccines and import regulations have virtually eliminated the major deadly contagious diseases of cattle in Canada. Historically, some of those infectious agents could also sweep through a herd causing massive mortality.

In summer, anthrax should always be considered on the Prairies. Outbreaks of this bacterial infection caused by Bacillus anthracis occur following flooding, drought or other phenomena that disturbs the soil. Affected cattle are usually found dead with unclotted blood draining from the nose and other orifices.

Die-offs from algal blooms can also cause high mortality in cattle herds. With hot temperatures, blue-green algae can overgrow in livestock water sources. The algal toxins cause rapid death by damaging the liver; dead cattle are often found near the scummy water source.

Blackleg, the vicious bacterial infection that leads to muscle damage and kills animals with deadly toxins, is also a consideration. This is a concern in herds that are not up-to-date on their clostridial vaccines.

Finally, poisoning is another way several animals could suddenly die. Any number of toxins are deadly to cattle, ranging from human-made chemicals to toxic plants. The key to investigating poisonings is to try to identify the most likely poison or toxin that the animal may have encountered.

Autopsy results in acute toxicities are often subtle and not specific to any one poison or disease.

Finding the potential culprit may take some boots on the ground to explore the pasture and enclosures. But this work is crucial to an investigation. Toxin testing is much more fruitful if the type of poison is narrowed down. Otherwise, it can be like searching for the proverbial needle in a haystack. And these types of tests can quickly become prohibitively expensive.

When trying to determine the cause of death in these situations, laboratory support is important. If possible, multiple animals should be autopsied to establish the pattern of disease. Testing takes time, so the sooner the samples are collected and submitted, the faster the results will be available. Most labs are closed or have limited capacity on weekends, which is another consideration.

In other words, don’t wait until Friday afternoon to call your vet to investigate sudden death in the herd.

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