Can Pine Needles Cause Abortions in Cows?
It’s best to keep pregnant cattle fenced out of pine trees during the second and third trimesters.
February 6, 2025
Pine needle abortion can cause significant losses for producers, but simple strategies can reduce the risk. [Photo by Adobe Stock Photo.]
by Bethany Johnston, University of Nebraska–Lincoln
Can pine needles cause abortions in cows? The short answer is “yes.”
Pine needle abortion can cause significant losses for producers, but simple strategies can reduce the risk. Check and repair fences around ponderosa pine trees to prevent losses in your herd, especially during the second and third trimesters. By excluding pregnant cows, you can avoid devastating losses.
Here are two real-life examples of producers who experienced premature calf losses.
Example 1: The Prairie Blizzard. Four lone pine trees were all that remained from the pioneers who tried to settle on the prairie. During a recent blizzard that dropped more than a foot of snow, it took several days for ranchers to reach their pregnant cows with hay. With drifts underfoot, the cows were tall enough to reach up and eat the pine needles out of the trees during the blizzard. A week later, half the cows prematurely lost their calves.
Example 2: The Old Farmstead. A neighbor purchased an old farmstead, which included a pasture where a shelterbelt of trees surrounded the buildings — pine and cottonwood trees. The buildings and wire fence that kept the cows out of the old shelterbelt had fallen down in disrepair, so the neighbor pulled the fence. His bred heifers wintered there, and more out of curiosity than anything, nibbled on the pine needles. Several heifers aborted that winter.
Both producers lost calves to pine needle abortions, as the cows and heifers “slinked” or calved too early, and the fetuses died.
Why do pine needles cause abortions in cows?
Since the 1920s, cattlemen wondered if ponderosa pine needles were causing abortions in their herds. From the 1980s to 1990s, researchers were able to determine that ponderosa pine needles did indeed cause abortions in pregnant beef cows.
Compounds in the Pinus ponderosa (or ponderosa pine tree) needles interfere with blood flow to the uterus and fetus, leading to premature births or fetal death.
Compounds in the Pinus ponderosa (or ponderosa pine tree) needles interfere with blood flow to the uterus and fetus, leading to premature births or fetal death.
Both green or dried needles from ponderosa pine trees, if ingested by pregnant cows, can be harmful. Cows would need to eat 3-5 pounds (lb.) of needles for several days to trigger an abortion. The later the trimester, the more susceptible cows are to pine needle abortion. In the third trimester, especially the last 30-60 days, cows can be more susceptible to pine needle abortion than early in the pregnancy. Low temperatures also seemed to increase pine needle consumption.
What animals are not affected by eating pine needles?
Cows that are not pregnant, steers and bulls are not affected if needles are ingested. Neither are pregnant elk, sheep or goats.
How to prevent pine needle abortions
What are solutions to avoid pine needle abortion? The simplest solution is to fence out ponderosa pine trees so that cattle cannot reach the needles to ingest them.
Another strategy is to adjust the calving season, so cows are calving in the summer or late fall, when they are less likely to eat pine needles in their second or third trimester.
Resources
- Management Strategies to Reduce Embryonic Loss
- Pine Needle Abortion — What We Know As Well As How To Predict/Prevent The Problem
- Ingestion of Ponderosa Pine Needles by Cattle
- Reproductive Toxicology: Pine Needles and Plant Estrogens
Angus Beef Bulletin EXTRA, Vol. 17, No. 2-A
Topics: Health
Publication: Angus Beef Bulletin
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