Ewe mastitis: Facts, symptoms and how to prevent it

Sheep farmers are being urged to focus on mastitis prevention strategies to reduce a problem thought to affect around a fifth of ewes in the UK.

Laura Green of the University of Warwick, who is leading an EBLEX-funded mastitis study, says the productive life of ewes would increase if mastitis and intramammary infections could be reduced.

Ewes that are affected have reduced or no production value in future years and the growth rate of their lambs is suppressed.

Prevention, insists Professor Green, needs to be a priority ahead of treatment. “Mastitis is a much bigger problem in a ewe than it is in a cow because treatments are not as successful. Using figures we have gained from other studies, I would estimate that about 12% of the national flock could be culled annually.”

The two-year EBLEX study involves 10 commercial and pedigree flocks in England, Scotland and Wales. Prof Green hopes the conclusions will provide the answers needed to reduce the incidence of mastitis.


The research project has been triggered by the concerns of producers about the disease, which according to recent evidence is already having a serious impact within the industry.

“Mastitis is a big problem and one of the reasons is that it is so unpredictable. One year, 1% of a flock might be affected and the following year it will be 5% and why this happens is largely unknown.”

Older and thin ewes are more likely to have a high SCC, as are those with poor udder and teat conformation.

In suckler sheep, mastitis can result in:

  • Permanent damage to the udder
  • Death of the ewe in severe cases
  • Culling of ewes at weaning because they will be challenged to rear twin lambs.
  • A reduction in lamb growth rates – those reared by ewes with a high somatic cell count (SCC) have been found to grow more slowly than the offspring of ewes with a lower SCC. The number of somatic cells increases in response to pathogenic bacteria such as Staphylococcus aureus, a cause of mastitis.


Symptoms and spread

Because sheep are handled much less frequently than dairy animals, farmers are often not aware that ewes have mastitis until they detect lumps in the udder at weaning or pre-tupping.

“Farmers don’t always remove all the ewes in the flock with lumps and bumps where we know there’s sub-clinical infection. We are looking to see if these ewes go on to develop clinical mastitis or are a source of infection,” says Prof Green.

Ewes can carry the bacteria which cause mastitis and it can be spread by lambs suckling. The principal bacteria is Staph aureus, but there are also environmental causes, such as E coli.

Where mastitis is seen early in lactation it is often due to Mannheimia, also known as Pasteurella. This can either come from ewes themselves or lambs may pass it to ewes when suckling.

Hygiene in and around the lambing shed is vitally important. Prof Green says feedback from farmers points to more mastitis cases when ewes are lambed inside, due largely to bedding being contaminated or ewes lambing in close proximity to each other and passing on infection.

Ewe mastitis facts

  • The bacteria which are known to cause mastitis in sheep are Staph aureus, E coli. and Mannheimia, also known as Pasteurella.
  • Mastitis usually occurs after lambing. With clinical mastitis the udder becomes swollen and warm, sometimes painful to the touch. Ewes become feverish, go off their feed and become depressed. They may refuse to allow their lambs to nurse.
  • Ewes with sub-clinical mastitis usually appear quite healthy but their milk supply is reduced and they develop lumps in their udders. Ewes need to be watched carefully to pick out these cases and prevent the potential damage.
  • Mastitis can be controlled with good management and sanitation. Bedding should be clean and dry and animals should not be overcrowded. There should be good drainage around the shed and lots.

She urges farmers not to skimp on bedding. “Everyone is tempted to save on bedding, but having analysed responses as part of this study there is a pattern emerging that farmers who bed up less frequently than once a day have more cases of mastitis.

“The message is that bedding needs to be clean and dry – particularly dry – as the bacteria thrive on wet straw.” There is also a higher risk of infection in warmer conditions.

Group yards housing ewes before lambing should be bedded regularly to ensure ewe udders are kept as clean as possible. Once ewes have lambed and are moved into individual pens these must also be kept clean.

Pens should be cleaned out between each ewe and a suitable disinfectant used before restocking. This will remove most of the organisms responsible for causing mastitis and should therefore be done as often as possible.

Body condition

Good body condition at lambing is also a useful preventative measure. Ewes with a good body condition score lactate better, meaning less butting from their lambs and reduced trauma to the udder.

“Butting can be quite harmful to the udder, it could be that it pushes sub-clinical infection into a clinical situation, and it does increase the risk of mastitis,” says Prof Green.

By monitoring ewe condition regularly, grazing and feed can be adjusted accordingly. Ewes should be grouped by condition score at weaning with the best grazing given to the leanest group.

Eight weeks on good grazing should raise body condition by one score with younger ewes tending to recover body condition faster than older animals.

The EBLEX study will also consider the contribution udder and teat shape have in reducing mastitis. “If we can define what the best shape is for feeding, this could well help to reduce mastitis rates,” says Prof Green.

Management at drying off is also important. Feet and udders must be routinely checked at drying off.


Ewes which show signs of mastitis should be treated with antibiotics. “Farmers should liaise with their vets on what is the most appropriate antibiotic for their situation,” she says.

She suggests collecting milk samples from affected ewes and freezing it so that if necessary they can be used to identify the main bacteria involved and the correct treatment to use. “A farm might be using certain antibiotics frequently and, because they are widely used, ewes may become resistant.”