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Pine needles harmful to cows?

Question: If cows eat pine needles, will it hurt them or cause a problem?

In general, yes pine needles can be a problem if cows consume them. Pine needles occur across much of the cow country in the western United States. However, there are some things that producers can do to protect their herds.

Pine needle toxins fall in the category of what is referred to as abortifacient and reproductive toxins. This means that they can cause abortions and upset the reproductive cycle of cows. In spring-calving cows, abortions usually occur in late fall or early spring (third trimester). The toxin that is involved with causing the abortions is isocupressic acid. It is important to note that the risk of pine needle poisoning increases after snow, wind, cold, changes in feeding conditions, and that both dry and green needles can cause abortion. In other words, if the cows get short on feed, they are more likely to forage on whatever they can find to satisfy their hunger and they may resort to eating pine needles.

There is also increased risk near logging operations, windfalls, dried fallen needles, and discarded Christmas trees. Lodgepole pine and common juniper also contain isocupressic acid. Therefore, it is important to take precautions when cattle have access to these species as well.

Abortions usually occur between 48 hours and 2 weeks after consumption of pine needles. It is interesting to note that the dose of toxin that causes abortion is variable with some cows being more sensitive than others. Abortions may range from just a few cows in the herd to 100%. Cows may show no other signs but the abortion of the calf. In cases where calves are aborted very late in pregnancy, they will likely be weak, and survival is low.

Several signs of pine needle toxicity are weak contractions, uterine hemorrhage, and incomplete dilation of the cervix. In addition, retained placentas are common with pine needle toxicity. Following abortion, cows may develop lesions, endometritis and septicemia, increased body temperature, and death if not treated.

Prevention of pine needle poisoning is quite straight-forward: Reduce exposure to pine trees, fallen needles, and slash piles during the third trimester of pregnancy. In addition, provide supplemental feed in cold weather or when snow covers dormant forage. The main point is don’t put hungry, pregnant cows in areas with lots of pine needles. Like with many other toxic plants, cows will avoid them if they have plenty of wholesome feed.

Adapted from:

There you have it, the story of pine needle toxicity in beef cows. Bottom line: Never turn hungry cows into areas with pine needles. Please let me know if I can assist you with your cattle feeding programs.

— Don Llewellyn

is the WSU Lincoln County Extension Director in Davenport. He can be emailed at


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