Tips for managing ewe mastitis during lambing

Mastitis in ewes costs the UK sheep industry more than £120m a year in direct and indirect costs, according to AHDB.

It is a primary cause of premature culling, loss of udder function, and reduction in milk yield. In worst case scenarios, it can lead to death.

Infection is particularly common in high-yielding breeds such as Poll Dorset and Suffolk, but all breeds are at risk if management during pregnancy and at lambing is sub-optimal.

See also: Tips for feeding and managing ewes for lambing success

AHDB’s Bethan John and Nerys Wright, who co-manage the Challenge Sheep project, advise on managing mastitis, as well as the signs and symptoms to look out for.

1. Hygiene in the lambing shed

According to Dr John, more than 30 bacterial species can cause mastitis in ewes – most commonly E coli and Staphylococcus aureus.

Practising good hygiene in the lambing shed is paramount.

Practically, this means keeping bedding clean and dry, and avoiding high stocking densities, which can otherwise provide a perfect environment for bacteria to thrive and increase the risk of infection in ewes.

Infection can also be spread through hands and contaminated clothing, so this should be avoided by washing hands regularly and wearing gloves.

When stripping ewes to check for mastitis, milk should be collected in a container, rather than onto bedding, to prevent contaminating the environment further.

2. Nutrition

High incidences of mastitis within flocks could be down to poor nutrition and, specifically, a lack of protein. This is thought to be one of the causes of acute mastitis during lambing and lactation.

Protein is the key building block in mammary tissue, and the level of protein fed in the last six to eight weeks of pregnancy can have a huge impact on milk production during lactation.

If milk production is sub-optimal due to insufficient protein, lambs will be hungry and return to the ewe more often to feed.

This can cause damage and trauma to the teats, which then provides the perfect habitat for environmental mastitis-causing bacteria to enter.

Checking protein levels in both the pregnancy and lactation rations ahead of lambing can help to minimise risk. Waiting until lambing to increase protein levels will often be too little, too late, says Dr Wright.

3. Body condition score

A body condition score below 3 at lambing (for lowland ewes) increases the likelihood of both clinical and subclinical mastitis, with thinner ewes at risk of not producing enough milk for their lambs.

If condition is on the poorer side, it is worth reviewing the ration with a nutritionist, as more protein and energy during pregnancy and lactation may be needed. Supplementation may also be beneficial for thinner or older ewes.

4. Teat and udder assessments

Shape and positioning of the udder and teats can influence mastitis incidences.

Teats placed on the outside of the udder, at a 45deg angle, are preferable to encourage suckling and minimise teat trauma, which reduces cases of mastitis. Ewes with poor conformation should be considered for culling.

Longer-term, genomic selection can help farmers to breed for better udder and teat conformation to reduce risk.

Heritability for chronic mastitis is estimated at about 10%, meaning it is highly heritable. Any mastitis-prone ewes should be removed from the herd and culled to improve flock health and productivity.

Causes, signs and symptoms of mastitis in ewes

What causes it?

Mastitis is caused mainly by bacteria but it can also be a symptom of a viral infection such as maedi visna.

A ewe has two lines of defence against mastitis: a physical barrier against bacteria within the teat, and her immune system.

Bacterial origins of mastitis can breach the physical barrier when the teat sphincter is open after suckling. It can often stay open for up to two hours after feeding.

Cells within the lining of the sphincter release keratin to prevent bacteria going up the teat.

However, if there is any damage or injury to either the inner lining or the sphincter itself, this is an opportunity for bacteria to enter.

Practically, these injuries might occur due to catching during shearing, or if lambs are nibbling and butting the teats, explains Bethan John of AHDB’s Sheep Challenge project.

If the ewe’s immunity is compromised in any way, this may also put her at greater risk of falling victim to mastitis.

What are the clinical signs?

Clinical cases can be divided into two categories – acute and chronic.

Acute is where the onset is rapid, and farmers are likely to see heat and swelling in the udder.

Ewes might also be hind-lame, unable to lie down, and – importantly at lambing time – unwilling to suckle.

Milk texture may also be affected, and can range from very watery to clotted with pus secretions visible.

If lambs appear to be very hungry, even after feeding, this might also be a sign of acute infection. In severe cases, ewes may get “black udder”, where the tissue becomes necrotic and can fall off.

Chronic mastitis is a longer-term challenge, and ewes which have had acute mastitis in the past are 12 times more likely to go on to suffer from intramammary abscesses, or masses. 

These masses are highly infectious and can damage parts of the udder not previously infected by the mastitis.

Subclinical signs include decreased milk yields and subsequent poor lamb growth. Somatic cell count testing may highlight the presence of infection, in the same way subclinical cases are detected in dairy cows.

What are the treatment options?

Injectable treatments including antibiotics and anti-inflammatories should be given as soon as a case of mastitis is diagnosed.

Typical treatment options include tilmicosin, amoxycillin and oxytetracycline.

The most effective option should be decided in consultation with a vet to ensure strategic treatment and best recovery of ewes.

Challenge Sheep update: Mastitis trends

The Challenge Sheep project began in 2017 with the aim of developing a best practice guide for managing replacement ewes during their first productive year.

The project also monitors factors on farm which cause ewes to leave the flock.

Insights from the five years of data collected so far show that 24% of the 7,000 ewes involved in the project have been culled or have died due to a known cause. 

Of that 24%, 21% of deaths/culling was due to mastitis.

“This is the single biggest known cause of why ewes are leaving the flock in the project so far,” explains Nerys Wright, who co-manages the project at AHDB.

The next stage of the project will include digging deeper into the variation in incidences between farms.

For more on mastitis management and Challenge Sheep, AHDB’s Bethan John and Dawn Bowness, from Clevedale Veterinary Practice, will be speaking at the webinar “Is ewe mastitis costing your business?” on Monday 20 February. Register your interest online.