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Mastitis in one or more mammary glands is caused by a variety of bacteria or it may be secondary to other diseases. It is a common condition that occurs sporadically in individual sows or sometimes as herd outbreaks. It starts around farrowing and becomes clinically evident up to 12 hours later. It can arise because bacteria have gained entry to one or more mammary glands for the first time, or it may be a flare-up of a long-standing sub-clinical latent infection. The route of entry of the bacteria is probably the teat orifice but it may be from the blood stream or by injection on piglets' teeth. It also commonly occurs at weaning time.

The bacteria that cause mastitis in the sow can be grouped into three broad categories: coliform bacteria, staphylococci and streptococci, and miscellaneous bacteria.

Coliform mastitis - Coliform bacteria are related to E. coli, the commonest being E. coli itself and klebsiella. They produce a severe acute mastitis which results in reduced milk yield, a very ill sow and poor "doing" piglets. Marked discoloration of the skin over the udder and dark blueing of surrounding skin, ears and tail is a feature.

Herd problems can develop because the organisms are present in faeces and may also be in sows' urine. Consequently, they may be everywhere in a piggery. Coliform mastitis may thus be regarded as environmental in origin.

Staphylococcal and streptococcal mastitis - These are usually less acute and less severe than coliform mastitis. They tend to occur sporadically in individual sows in one or more glands and usually do not make the sow ill. The exception is an acute severe staphylococcal infection usually in a single gland which becomes swollen, hard and discoloured and makes the sow toxic.

Unlike coliform bacteria the source of these organisms is not usually the contaminated environment but the skin and possibly orifices of the sow herself. There is some evidence to suggest that as in the dairy cow and sheep some of these bacteria may persist sub-clinically in the udder and then flare up at or after farrowing

Miscellaneous bacteria - These include organisms such as pseudomonas which can produce a serious mastitis and toxaemia and which are often resistant to antibiotic treatment. Fortunately such infections are rare.


  • Hungry.
  • Thin.
  • Squealing due to lack of milk.

Acute disease

  • Inappetence at farrowing or before if mastitis is already developing.
  • Obviously ill will not suckle.
  • Fever.
  • Mucous membrane of her eyes are brick red.
  • Affected glands swollen, red colour and painful.
  • Discoloration of the ears and the whole of the udder, but particularly over the affected glands.
  • Blue skin.
Chronic disease (Usually seen in dry sows):
  • Mammary tissue is infiltrated with hard lumps that are usually not painful when palpated.
  • They may ulcerate to the surface and become a potential source of infection to other sows.
Weaners & Growers
  • N/A

Causes / Contributing factors

  • The continual use of farrowing houses.
  • Poor farrowing pen hygiene, bad drainage, inadequate and poor quality bedding.
  • The use of saw dust or shavings for bedding that become soaked in water or urine.
  • A warm temperature for the organisms to multiply.
  • Worn pitted farrowing house floors.
  • Wet farrowing house floors.
  • Contaminated drinking water.
  • Adverse temperatures, draughts and poor ventilation in the farrowing houses.
  • A build up of faeces behind the sows.
  • Klebsiella in the water system.


The clinical signs are usually sufficient to diagnose mastitis. However if there is a herd problem with a number of sows affected, you should examine all animals clinically at farrowing and again at weaning, to determine the starting point of the mastitis. A sample of the secretions from the infected quarters should be submitted to a laboratory for examination. This is carried out by wiping the teat end with cotton wool soaked in surgical spirit, injecting the sow with 0.5ml of oxytocin and once there is a good flow squirt the milk on to a sterile swab. The swab should be immersed in a transport medium. It is very important that mastitis is diagnosed early and that prompt treatment is given.

Further Reading

Click on the links below to find out more about this disease, including treatment, management control and prevention information. The top link is the main article on this disease.