How We Can Manage and Learn from Bovine Pregnancy Loss

Discover essential strategies for managing pregnancy loss in dairy herds, including understanding causes, diagnostics, and prevention to improve overall herd health.

By Dr. Greg Goodell, Owner, The Dairy Authority, LLC

The loss of a pregnancy is never good news on the dairy. But when it happens, it’s important to do our best to investigate the cause. Was it an isolated incident, or a bellwether for a broader disease issue in the herd?

Recording abortions and monitoring that data also is critical to track changes over time. Is the herd experiencing a growing number of abortions, or even an “abortion storm?” If so, diagnostic work and management changes are needed to get ahead of the problem.

When we talk about abortions, it’s important to first define what an abortion truly is. The loss of a pregnancy is broken into three categories based on fetal age:

  • Early embryonic death (EED) – Loss of the conceptus before day 42 of gestation. 
  • Abortion -- Loss of the fetus between days 42 and 260 of gestation. 
  • Premature delivery – Loss of the fetus after 260 days of gestation.

The “normal” range for total pregnancy loss on dairies is around 5-15% of all conceptions, although a good share of those are due to EED. A typical, visible abortion rate is about 2.5%, but this figure also can be highly variable.

A herd’s timing and method of pregnancy diagnosis can influence the detection of EED. It is reported to occur in about 10-15% of pregnancies between 28 and 45 days, but that rate can vary widely depending on whether a dairy’s pregnancy checks commence at 28 days versus 35, for example. 

Whether a dairy diagnoses pregnancy via rectal palpation, ultrasound, or chemical methods (blood or milk) also has a bearing on these numbers, as does the use of embryo transfer and ovum pick-up.

Unfortunately, many dairy management software programs record EED as an “abortion” despite the fact that they are not the same thing, and likely have different causes. EED can be triggered by heat stress, nutritional deficiencies, chromosomal abnormalities, postpartum uterine condition, and/or hormone imbalances, among other issues.

True abortions fall into two categories; (1) infectious; and (2) non-infectious. Infectious abortions are more typically caused by agents like bovine viral diarrhea virus (BVDV), neospora, listeria, leptospirosis, aspergillus, bovine herpesvirus, campylobacter, salmonella, and tritrichomonas (in bull-bred herds). Non-infectious abortions are a result of genetic factors, toxic agents (mold, plants, etc.), health events (toxic mastitis) and environmental factors such as heat or severe weather patterns.

If possible, create customized reports within your dairy software system to separately track EED and true abortions monthly. The abortion category should include data from “invisible abortions” – cows that were confirmed pregnant but found open or in heat later, even though their fetal loss was not physically observed.

This type of herd surveillance is the most important thing you can do to detect and remedy issues that are interfering with reproductive and pregnancy success in your herd. And while no one likes abortions, they may be an early, telltale indicator of diseases that put your herd at risk of other, severe health and production setbacks.

When you do discover an aborted fetus, this creates an important opportunity to pinpoint and address the causative issue. Your herd practitioner from The Dairy Authority can coach you on the protocol for submitting an abortion kit, which will be completely evaluated at our in-house laboratory. The elements for a full abortion diagnostic work-up include:

  • Blood samples from the dam, taken 17-21 days apart. This allows us to perform paired serological testing to see if the dam has gone through a change in antibody titers related to specific diseases.
  • Fresh tissue from the fetus, which will be evaluated with tissue cultures from various parts of the anatomy.
  • Fixed fetal tissue, preserved in formalin, which will be used to conduct microscopic evaluation of tissues to look for abnormal disease signs (histopathology).
  • Placenta for culture and histopathology.
  • Vaccination history of the dam.

While not all abortion diagnostic work-ups are conclusive, submitting these samples and information can make it up to five times more possible for us to achieve a diagnosis of the abortion’s cause. 

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