News & Advice

Black Mastitis

Aug 3, 2021 | Dairy, Dairy Animal Health & Welfare, Milk Quality

Jemma Guyton, Veterinarian, Anexa Vets Matamata

If you’re lucky, you’ll go through your whole farming career without seeing a case of black mastitis, but many of you will likely have seen it before. 

Black mastitis or gangrenous mastitis can be caused by many different bacteria not just from Staph aureus or E.coli. It occurs during times when a cow’s immune system is suppressed i.e., around calving or when cows are sick, weak, down or have low energy to fight infection. A suppressed immune system means the bug can really take hold and produce toxins, but the cow’s immune system is not strong enough to fight the infection. 

How does it usually appear and progress?

  • Rapid onset
  • Cows may appear lame on the affected side
  • Quarter initially swollen and hard
  • Blueish skin discolouration over the affected quarter
  • Affected teat usually becomes cold to the touch
  • Discoloured areas then become black and may ooze fluid or blisters may form
  • Milk from the quarter is usually dark or blood-stained
  • Toxic cows often depressed and toxic with fast, shallow breathing
  • Temperature may be below normal or high
  • Often cows go down and die

The prognosis for cows with gangrenous mastitis is poor. Euthanasia is often the preferred treatment, particularly if more than one quarter is affected.

If you decide treatment is unlikely to be successful, you must humanely euthanise the animal on farm. You cannot send a cow with black mastitis to pet food as she will not be accepted.


How is it treated?

Treatment of these cases is aimed at saving the cow’s life; the quarter will already be lost. Treatment usually includes:

  • Intravenous antibiotics
  • Intravenous anti-inflammatories
  • Oral fluids (with electrolytes) by stomach pump 

The use of intramammary tubes is of little value as the antibiotics can’t diffuse through the affected gland. Instead focus on systemic treatments with antibiotics.


If the cow survives, then what happens?

If you save the cow and choose to persist with her, the road ahead is long and not particularly pleasant. The affected quarter will eventually die off and slough, leaving a large core of udder tissue hanging out before it eventually falls off over a period of 1-2 months (sometimes longer). Once the core falls off, the body then does it’s best to heal and close over the wound, leaving a scared, often misshapen area on the udder.

To assist with healing, you can use antibiotic spray, udder cream or teat spray and spray the sloughing tissue. There is some evidence that zinc cream can also help with healing.


Can you prevent black mastitis?

No matter what, cows live in environments where there is always a risk of picking up mastitis bugs.  However, cows in good condition, that are well fed and transitioned, and not fighting disease will have better immune function, which helps them fight infections easier!


Here are some more tips and tricks specific to calving time:

  • Focus on the transition period and getting this right, so metabolic disease is minimised. Cows with metabolic disease have a much tougher time fighting infections as they are immunosuppressed. 
  • Check your springing and freshly calved cows for mastitis often! If you find a cow with a black quarter, it usually means that she has had mastitis for at least 3-4 days.
    • A lot can happen in 24 hours! If you milk colostrum cows or sick cows once a day, you are only able to closely observe cows and their udders once a day. This means mastitis can progress without intervention and can be the difference between life and death for a cow with black mastitis.
  • Calve your cows down on the cleanest possible area to limit the opportunity for bugs to enter teat canals.
  • Hygiene during milking is key! 


Anexa info flyers you might find helpful:

Hand hygiene poster (dry off).pdf

How to collect a milk sample.pdf

How to RMT Rapid mastitis test.pdf



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