Diagnosing the Cause of Late-Term Abortions

By : Russ Daly, DVM, DACVPM, Professor, SDSU Extension Veterinarian, State Public Health Veterinarian, SDSU Veterinary & Biomedical Sciences Department, Courtesy of iGrow.org


Reproduction drives our livestock industries. Animal health and nutrition interventions are meaningless if those animals are never born in the first place. Efficiency in reproduction can make or break a beef operation.

All the way from conception to birth, we depend on a lot of things to go right, whether we are talking about natural or artificial breeding programs. Reproductive failure can present itself in many ways; the most dramatic of which is abortions (miscarriages) of the late-term (older) fetus.

It’s difficult to pinpoint exactly what went wrong with many of those cases. All livestock producers expect a certain degree of late-term abortions or stillbirths. It’s generally accepted that any cattle operation will have 1-2% of “normal” pregnancy loss after a month or two of gestation.

What causes these problems? January and February is when many abortion cases are submitted to the SDSU veterinary diagnostic laboratory. In about half of these cases (across all diagnostic labs) no abnormalities are detected. There are many reasons for this. In addition to the fact that infectious agents often aren’t detectable anymore by the time the fetus is expelled, stillborn calves caused by prolonged labor will usually not exhibit lab abnormalities. Twin pregnancies are notorious for stillbirths as well.

In the rest of the cases, something abnormal is found. A frequent finding is inflammation in the placenta that may or may not be traced to a specific germ. The placenta in a pregnant animal is the gateway from the mother’s blood supply (carrying nutrients and oxygen, but possibly bacteria and viruses) to the fetus. If something affects that critical tissue, then the fetus may become starved for oxygen and die. For that reason, the placenta should be included along with fetal tissues when submitted to the lab.

When germs are found, they are often more environmental than contagious in nature. For example, Bacillus is a bacteria common to pasture and cattle lots. Every cow is exposed to this germ every day, but only a few experience problems. Molds are much the same way, and are commonly encountered in hay or other feedstuffs. Sometimes infectious agents such as IBR, BVD, or leptospirosis are identified, for which effective vaccines are available.

So what should cattle producers do when these late-term abortions are encountered, and what can be done to prevent them? The answer starts with your local veterinarian. They know what’s going on in your particular area and what gives the best chance of a diagnosis.

First, consider submitting the aborted fetus and placenta to a veterinary diagnostic lab. Once one or two abortions have been observed, it’s generally time to get a diagnosis. Do your best to get placenta from the cow as well as the fetus for your vet to send in, along with a good history of events. Have a good discussion about the results with your veterinarian. Even if an environmental cause, such as mold or Bacillus, is identified, there may be interventions that could help – especially examining the quality of feed sources.

Lastly, look to ensure you have a good pre-breeding vaccination program for next year. Focus on preparing heifers well in advance of the breeding season, and get guidance from your veterinarian. Using vaccines before the breeding season is best from a timing standpoint.

With reproduction, focusing on what we can control and diagnose is the key to helping avoid reproductive loss within our livestock. For more information please feel free to contact SDSU Extension Veterinarian Russ Daly.

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