General description

There are many different types of cancer (malignant tumour) that can affect livestock, however most are rare. In Australia, the most common sheep cancers affect the skin and eyes, and are caused by the sun's ultraviolet radiation irritating exposed areas of the skin. But cancer can have other causes and affect other organs too.

If malignant tumours are found in animals slaughtered at abattoirs, all or part of the carcass may be rejected.


  • Sheep that have been badly mulesed, or had their tails docked too short are predisposed to cancers.
  • Sun damage to bare areas of unpigmented skin plays a large role.

Clinical signs

  • Skin cancers begin as red, sun-damaged patches.
  • As the tumour grows it may cause severe irritation and distress to the animal


  • Diagnosis is confirmed after microscopic identification of the tumour tissue.


  • A veterinarian can successfully treat early stages of some cancers by surgically removing the affected area and/or treating it with cryosurgery (freezing) or radiation.


  • Leaving skin on top of the tail during the mulesing operation and permitting tail length to extend to the tip of the vulva will offer some protection.