In this article:
- What are the most common causes of bovine abortion?
- How should results be interpreted?
- When should producers begin to investigate abortions in their herd?
- How does tracking pregnancy status improve abortion case evaluation?
- Why is immediate specimen submission so important?
- What specimen should be submitted for an abortion investigation?
- What happens once specimens arrive at TVMDL?
- How does TVMDL support veterinarians and producers facing bovine abortion?
Bovine abortion often leads to significant biological and economic consequences for cattle operations. With today’s high cattle values and the increasing cost of replacement heifers, these losses can quickly become financially devastating.
Pregnancy loss may also indicate underlying infectious disease, which can affect the entire health of a herd. For these reasons, prompt investigation and a comprehensive diagnostic evaluation are essential.
This article summarizes key insights from veterinary professionals discussing bovine abortion, including why abortions occur, how cases are investigated, and what steps veterinarians and producers can take to protect herd health.
What are the most common causes of bovine abortion?
When abortions occur, it is very instinctual to point to an infectious etiology. However, the cause of most bovine abortions is unknown.
Even with modern diagnostics, identifying the exact cause can be difficult. However, several infectious and non-infectious agents are known to contribute to bovine abortion.
Infectious causes
Infectious agents are often the focus of diagnostic workups because they can spread within a herd, and most can be identified with diagnostic testing of appropriate samples.
Bacterial agents
- Brucella abortus
- Leptospira species
- Campylobacter species
- Listeria monocytogenes
Viral agents
- Bovine Herpesvirus type 1 (BHV-1) causes Infectious bovine rhinotracheitis (IBR)
- Bovine viral diarrhea virus (BVDV)
Protozoal agents
- Neospora caninum
Other infectious causes
- Fungal infections
- Mycotoxins associated with poorly stored or moldy feed
Non-infectious causes
Abortions may also result from non-infectious causes, such as:
- Nutritional deficiencies
- Mineral imbalances
- Trauma
- Environmental stress
- Toxin exposure
- Genetic abnormalities
How should results be interpreted?
A positive identification of a pathogen in the fetus or a significant antibody response in the dam may confirm the cause of abortion.
Some infectious causes of abortion have regulatory implications. For example, detection of brucellosis may require state or federal reporting.
In other cases, results may sometimes be inconclusive. When this happens, veterinarians may examine patterns within herds, such as:
- Multiple aborted fetuses with similar lesions
- Rising antibody levels among cows
- Clusters of abortions within a specific time frame
These patterns can still help guide herd-level management decisions even if a single causative agent is not confirmed.
When should producers begin to investigate abortions in their herd?
The decision to initiate an abortion investigation often depends on the individual operation and its goals, but most veterinarians recommend investigating when abortion rates reach 2–3% of pregnancies or higher.
Even seemingly sporadic cases can signal the start of a larger issue.
Producers should contact their veterinarian if they observe:
- Abortions occurring in clusters
- Multiple aborted fetuses or placentas
- Other cattle showing signs of illness such as:
- Fever
- Diarrhea
- Vaginal discharge
- Foul or fetid odor
Early communication with a veterinarian is critical because quick action can help limit the spread of infectious disease and increase the chances of identifying a cause.
How does tracking pregnancy status improve abortion case evaluation?
It is highly recommended to work with a veterinarian to perform routine pregnancy checks, as this provides a reliable way to monitor reproductive performances and establish a clear baseline within the herd. Having this information in place makes it much easier to recognize when fetal loss is occurring and to distinguish true abortion events from cows that were not confirmed to be pregnant. With consistent monitoring, producers and veterinarians can more quickly identify changes, respond earlier, and make more informed decisions when concerns arise.
Why is prompt specimen submission so important?
The fresher the samples, the higher the testing quality. As time passes and tissues decompose, important lesions may disintegrate, and diagnostic clues may be lost. In addition, unrefrigerated samples can allow bacterial overgrowth, which may obscure the true cause of abortion. Prompt sample submission allows for the preservation of tissue integrity and the most advantageous microscopic evaluation.
What specimen should be submitted for an abortion investigation?
For the most complete diagnostic workup, veterinarians typically recommend submitting:
- The entire fetus (chilled, not frozen)
- Placenta, if available
- Maternal blood (serum)
Importantly, aborted tissues can carry infectious agents that pose risks to both humans and animals, so proper protective equipment, such as gloves, should be used, birthing material should be cleaned and removed from the pasture or barn, and access to the area should be limited.
Additionally, clinical history should also be included in the overall submission. Key information that should be provided may include:
- Herd size
- Number of affected animals
- Vaccination history
- Feeding and management practices
- Recenenvironmental changes or herd additions
What happens once specimens arrive at TVMDL?
Once samples arrive at TVMDL, they are processed through a structured diagnostic approach designed to identify the cause of abortion as accurately and efficiently as possible. This process may involve several steps.
Gross examination and necropsy
Veterinary pathologists often begin with a necropsy of the fetus, carefully examining tissues for abnormalities that may suggest a cause of death. During the necropsy, tissues are collected for further testing.
One particularly valuable sample is abomasal fluid, which represents the contents of the fetal stomach. Because the fetus swallows amniotic fluid while in utero, abomasal fluid can provide insight into the intrauterine environment prior to abortion. This makes it especially useful for detecting infectious agents or other abnormalities that may have contributed to fetal loss.
Histopathology
Formalin-fixed tissues are examined microscopically to identify lesions associated with infection, inflammation, or developmental abnormalities.
Microbiology and pathogen detection
Several other tests may be performed, including:
- Bacterial culture
- Fungal culture
- PCR testing for pathogens such as:
- Neospora
- BVD virus
- Leptospira
- Bovine herpesvirus-1
- Virus isolation
Serology
Blood samples from the dam may be tested for antibodies against specific pathogens, including:
- Brucella
- Leptospira
- Neospora
- BVD virus
How does TVMDL support veterinarians and producers facing bovine abortion?
TVMDL supports veterinarians and producers facing bovine abortion by providing timely diagnostics and expert consultation.
TVMDL also collaborates with state animal health authorities to help control disease outbreaks and protect livestock populations.
With excellent service and care, TVMDL helps producers find answers and protect the long-term health and productivity of their herds, protecting health and minimizing financial losses.
Clients seeking detailed guidance on reproductive diagnostics can visit tvmdl.tamu.edu or call the College Station laboratory at 888.646.5623 or the Canyon laboratory at 888.646.5624 to consult with a veterinary professional.