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Dangers of bovine leukosis are heavy on a herd

John Langdon for Progressive Cattle Published on 23 October 2020

Bovine leukosis is a very common enzootic infection in beef cattle, caused by the virus bovine leukemia virus, that can be transmitted between cattle by means of infected blood – mostly through infected needles, eartagging/tattoo equipment, dehorners, A.I. sleeves and some insects.

Once the virus enters into the animal’s bloodstream, the animal becomes infected and will be infected for the duration of its life. Some calves out of infected dams have been infected. Most reported cases of infection in calves are due to consumption of infected milk or colostrum. In mature cattle, the infection will sometimes cause cancer, can then be detrimental to the animal and can (in many cases, once the cancer has developed) lead to what can often appear to be an unexplainable death.

Sometimes tumors are visible; other times, they are not. Tumors can sprout up in about any place in the animal’s body. And symptoms can vary widely upon location of tumors. In cases I have observed, the cancer manifested itself in the animal’s spinal region and may have been the cause of the animal going down and not being able to get back up. Only a couple of days later, the animals had deceased.

Keep in mind, the infection has rarely been observed to cause cancer, death or any other noticeable deleterious effects when the animals’ plane of nutrition is adequate, when parasite load is minimized, when body condition is sufficient for cow maintenance and reproduction, and when aged cows are cared for properly and/or culled.

How to test for bovine leukosis

For live or deceased animals, you can draw a good blood sample with needle and syringe. Fill up one to two 10-millilter test tubes and take them to your local veterinarian. A test can then be done which will yield conclusive results for you within a few days. For deceased animals, the blood test works, although a necropsy is the most conclusive. I recommend you give your veterinarian a call for the most specific instructions.

If some of your herd turns out to be bovine leukosis-positive

If some percentage of your herd is positive for bovine leukosis, you will need a working strategy in place for long-term (and short-term) management. For the short term, remember that the infection has rarely been observed to cause cancer, death or any other noticeable deleterious effects when the animals’ plane of nutrition is adequate (feed your cattle adequately), when parasite load is minimized (deworm, delice, etc.), when body condition is sufficient for cow maintenance and reproduction, and when aged cows are cared for properly and/or culled.

Nevertheless, from a long-term perspective, separating bovine leukosis-positive animals from negative animals will eventually be necessary to prevent further spread. Furthermore, culling the positive animals will need to be done. Replace them with healthy breeding stock. This is a worthy investment.

The idea of trying to sell animals positive for bovine leukosis is not a good policy, in any type of market. Also, marketing tumored animals to slaughter will likely be condemned. Additionally, it becomes much more challenging to sell bovine leukosis-positive animals for production and reproduction the higher up the marketing chain you are aiming to sell in (seedstock, bull studs, etc.).

Conclusion

Manage well in the short term as you plan to improve for the long term. Test your herd for bovine leukosis. Knowledge is power. Truth is useful. Separate the negative group from the positive group. In the short term, you can manage the positive group in an adequate health management program of your making, selling them off and buying healthy replacements to put in with the negative group to slowly rebuild a completely bovine leukosis-free/negative healthy herd, over time. I recommend using a sterilized needle for each animal, no reuse of A.I. sleeves (use a new one for each female) and sterilizing any equipment of risk between uses.  end mark

John Langdon
  • John Langdon

  • Livestock Specialist
  • SE Central Missouri
  • University of Missouri Extension
  • Email John Langdon

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