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Gangrenous mastitis
Gangrenous mastitis is the most serious form of udder infections. Bacteria producing toxins destroy the blood circulation in the area within a few hours: it cools, takes on a bluish tint then black, and the tissue dies. The toxins pass into...
What is it?
Gangrenous mastitis is the most serious form of udder infections. Bacteria producing toxins destroy the blood circulation in the area within a few hours: it cools, takes on a bluish tint then black, and the tissue dies.
The toxins pass into the blood and poison the entire body. The cow can die in one to two days, sometimes even before the udder is really black.
It most often occurs at the very beginning of lactation, in the days following calving, but also in lactating cows and in ewes and goats.
Key point
Veterinary emergency: the cow can die in one to two days. A cold, blue or black neighborhood with a slaughtered cow requires an immediate call.
Commonly observed signs
These signs are neither exhaustive nor specific. Only a veterinarian can establish a diagnosis.
Related signs — each one links to its page:
A quarter suddenly very swollen, hard, extremely painful to the touch.
The skin in the neighborhood changes color: first dark red, then purplish, bluish, finally black. The quarter becomes cold to the touch while the cow has a fever: this is a characteristic and alarming sign.
The milk is profoundly abnormal: reddish or brownish liquid, sometimes serous and malodorous, mixed with debris; it may become impossible to extract.
High fever at first, often followed by a drop in temperature, a sign of seriousness.
Deep depression, total refusal of food, cessation of rumination.
Rapid dehydration, sunken eyes, abnormal mucous membranes, rapid breathing.
The cow limps or refuses to place the limb on the affected side because the udder is so painful.
In advanced forms, the cow remains lying down and never gets up.
Later, a clear dividing line appears between the healthy skin and the dead part, which gradually peels off, leaving a wound.
When to consult without delay
This list does not replace veterinary advice. It gathers situations that justify a prompt consultation.
Causes and risk factors
The infection is caused by bacteria capable of producing toxins that destroy the blood vessels in the udder. Some are germs from the skin and udder, others come from litter and the environment.
The toxins cut off circulation in the area: deprived of blood, the tissue dies, which explains the cooling and blackening.
The same toxins pass into the general circulation and cause the shock state which threatens the life of the cow.
Teat injuries, stings, bites and cracks are common entry points.
The period immediately following calving is the most at risk, as the cow's defenses are then at their lowest.
Start of lactation, especially the first days after calving.
Teat injuries, cracks or trampling; calf bites in lactating cows.
Soiled and damp litter, dirty housing, high density of animals.
Insufficient milking hygiene and lack of teat disinfection.
Poorly adjusted milking machine which damages the end of the teat.
Poorly managed dry-off, unprotected udder during the dry period.
Cows that have already had mastitis, hanging udder, teats close to the ground.
Heat and humidity, which accelerate the multiplication of bacteria.
Diagnosis and care
Diagnosis is the veterinarian's responsibility, based on clinical examination and laboratory tests. Care is decided case by case.
Call the veterinarian immediately, without waiting until the next morning. Every hour counts.
In the meantime, isolate the cow in a clean, dry and shaded place, provide her with clean water and do not move her more than necessary.
Do not treat yourself or inject anything into the breast: this delays treatment and confuses the examination.
The veterinarian assesses the general condition – temperature, circulation, hydration – because it is he who determines the prognosis, even more than the appearance of the area.
He examines the udder, palpates it, assesses the extent of the affected tissue and the limit of the dead zone.
A sample of milk or liquid from the quarter can be taken to identify the bacteria and tailor treatment.
Treatment
The treatment is veterinary, hospital in principle, and it aims first to save the cow, then only the quarter - which is most often lost.
It combines general antibiotic treatment, anti-inflammatories for pain and shock, and massive rehydration by infusion.
Milking or frequent emptying of the affected area is practiced when possible, to evacuate toxins.
Depending on the evolution, the veterinarian can make incisions to drain the dead area, remove the destroyed tissues, or decide on surgical intervention on the area.
Local wound care following the shedding of dead tissue lasts weeks and must be carried out according to the veterinarian's instructions.
When the cow is too affected and suffers without hope of recovery, euthanasia is considered: it is a decision that is made with the veterinarian, while respecting the well-being of the animal.
After any treatment, the waiting period for milk and meat set by the veterinarian must be strictly respected, including for milk from healthy quarters.
Treatment depends on the cause and the animal's condition: it must be determined by a veterinarian. No self-medication.
Prevention
Milking hygiene and properly managed drying off remain the heart of prevention, as with all mastitis.
Disinfect the teats after each milking and treat the slightest crack or injury without delay.
Maintain abundant, dry and clean bedding, especially in the calving box and for freshly calved cows.
Monitor the cows' udder very closely in the days following calving: feel, look, draw out the first jets every day.
In lactating cows, regularly check the udder, which is looked at much less than that of dairy cows.
Have the milking machine checked and replace worn sleeves.
Protect the udder from drying off according to the plan established with your veterinarian, and keep dry cows in clean housing.
Fight against flies in summer: they cause lesions on the teats.
Promptly isolate and treat any visible mastitis before it escalates.
Possible complications
Cow dies in one to two days from shock due to toxins.
Permanent loss of the neighborhood, which will never produce milk again.
Falling off of dead tissue leaving a large open wound, which takes a long time to heal and is exposed to infections and flies.
Secondary infections and spread to other organs.
Significant weight loss and lasting drop in production for the entire lactation.
Frequent culling of surviving cows.
When to see a veterinarian
A quarter is suddenly swollen, hard and very painful: call immediately.
The skin of the udder becomes purplish, bluish or black.
The neighborhood is cold while the cow has a fever.
The milk looks like a red or brown liquid, smelly, or no longer comes out.
The cow no longer eats, no longer ruminates, is depressed or refuses to get up.
She limps or refuses to pose on her bottom because of the pain in her udder.
Any mastitis in a freshly calved cow that is accompanied by fever and depression should be seen immediately.
Prognosis
The vital prognosis is guarded and depends directly on the speed of the intervention: treated in the first hours, some of the cows survive.
The affected quarter is almost always lost permanently, even in cows that recover.
Cows that survive often have a wound that takes weeks to heal and produce significantly less during the current lactation.
A cow in shock, lying down and unable to get up at the time of examination has a poor prognosis despite treatment.
Frequently asked questions
Why is the neighborhood cold when the cow has a fever?
Because the toxins have blocked the blood circulation in the area: deprived of blood, it cools and dies, while the rest of the body reacts with fever. This is a very suggestive sign of gangrenous mastitis and a reason for immediate appeal.
Will the neighborhood produce milk after healing?
No, in almost all cases. Destroyed tissue does not regenerate. The objective of the treatment is to save the cow and preserve the other quarters.
Can I sell milk from healthy neighborhoods?
Not during treatment. The drugs pass into all of the cow's milk: all of its production must be discarded until the end of the waiting period set by the veterinarian.
Can this happen to a nursing cow that is never milked?
Yes, and it is even a risky situation because the udder is less often observed. A lactating cow that is limping, isolated or whose calf is suckling poorly should have its udder checked without delay.
References
FAO — Organisation des Nations unies pour l'alimentation et l'agriculture
Content reviewed by the TunisieVet editorial team · Updated 09 August 2026
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