Investigating Cattle and Sheep Abortions

Date published: 24 February 2026

Spring is fast approaching and soon the fields will be filled with lambs and calves playing through the grass.

Spring calving and lambing season is a busy time for farmers and vets alike. However, this time of the year is also an important time to assess the health of flocks and herds. One way of doing this is by looking at the lambing/calving percentage or the number of abortions/stillbirths.

Abortions and stillbirths have a range of causative agents including infectious diseases, mineral deficiencies, and trauma to or systemic conditions affecting the dam (e.g. pyrexia). Abortions may occur individually or could indicate the start of an abortion storm. Therefore, investigations of all incidents of abortion or a representative number of aborted foetuses (including their associated placentae) is recommended, as more than one agent may be involved.

Determining the cause of abortions and stillbirths is vital so that management steps can be taken on farm as soon as possible. For example, changing feed management if Listeria monocytogenes or Bacillus licheniformis are detected. Other steps may include immediately starting a vaccination program or vaccinating before the next breeding/calving/lambing season depending on the disease detected. It is important to consider that the submission of abortion material is as much to rule out common causes of abortion as to rule in others. If infectious causes are not detected this may indicate the cause of the abortion is metabolic or due to placental failure for example.

Abortions and stillbirths along with placenta and dam’s blood (if available) can be submitted to your local AFBI postmortem diagnostic laboratory, with one located in Omagh and another at Stormont. At AFBI foetal material can be tested for a variety of infectious causes of abortion. If you are unable to bring foetal material to the labs, please speak to your veterinarian as they may be able to collect the samples themselves. However, as the postmortem labs sample a large variety of tissues, complete on-farm sampling may not be possible and hence diagnosis on these cases may be compromised.

All cattle abortions, stillbirths, and calves dying within 24 hours of birth should be reported to DAERA, and if notifiable disease is suspected or detected, DAERA should be contacted immediately.

The submission of abortions, stillbirths, weak or deformed ruminant neonates is particularly important this spring with the first detection of Bluetongue virus (BTV) in Co. Down in November 2025. This virus which is spread by midges is teratogenic meaning it can pass across the placenta in an infected dam to infect the foetus. BTV can cause deformities of the joints (arthrogryposis) which are obvious, while other deformities may not be visible without assessing the brain of the foetus. Deformities can appear similar to those caused by other viruses including Schmallenberg and BVDV, which makes it impossible to differentiate the virus involved without further testing.

During the month of January, we have seen many different causes of abortion including an increased number of bovine abortions due to Leptospira, abortions due to BVDV, and other bacterial agents such as Trueperella pyogenes, Listeria monocytogenes, and Bacillus licheniformis. Ovine abortion agents including Toxoplasma gondii and Chlamydia abortus (enzootic ovine abortion) have also been identified.

If your farm is experiencing an issue with fertility or increased incidence of abortion this spring, it is important to speak to your vet to decide the next steps to determine the underlying cause. The only way of confirming the cause of an abortion is by carrying out testing on the foetus. To do this, it is best to send the foetus and its placenta to an AFBI postmortem lab. However, given the time constraints of the upcoming Spring season, vets can contact the labs to determine the best samples to take if they wish to complete on-farm sampling.