So Lush, So Green, and Oh So Poisonous

You better not feed yew to the ewe (and other livestock)

In memory of livestock that met “Their Maker” because they ate yew.

It’s that time of year when the yew (pronounced like the letter “U”) is likely in need of a trim to look best as a landscaping plant. Yews have been used as a common landscaping shrub or small tree for decades. They have closely spaced, glossy, rather tough, dark green, linear pointed-end leaves that are 1.5 – 2 inches long.  Hard-to-see male and female flowers are found on separate plants and form fleshy red to yellow fruits that contain a single seed.

Many plants have poisonous compounds that can cause all kinds of concerns, and even death, if consumed. The interactions that I have had with veterinarians, suggest that the yew is right at or near the top of plants that cause livestock death. A disheartening scenario is when yew trimmings are thrown over the fence by the livestock owner or neighbor thinking that the trimmings would make a great snack for the livestock. Fresh or dry trimmings, it doesn’t matter. The result will be the same – death.

The following information about yew is from the Purdue University toxic plant exhibit website Toxic Plants (purdue.edu). The live plant exhibit is located at the Southern Indiana Purdue Agricultural Center and next to the Heeke Animal Disease Diagnostic Laboratory. Information about 21 different plants that are known to be potentially poisonous are found at the live plant exhibit and at the website.

Time of Most Concern:

• When clippings are placed in pastures, when livestock get out of pasture and find yews in landscapes, or when the older leaves are consumed
• All seasons of the year

Compound that Causes Concern:

• Perhaps an alkaloid; taxine

• Separated into two fractions, taxine A and taxine B. – Taxine B is present in the greatest amount

• Alkaloid does not act as a cardiac glycoside but depresses conduction of depolarization through the heart
• Taxine and other diterpenoid alkaloids contain a slow-to-act gastrointestinal irritating oil

Part of Plant Most Toxic:

• Older leaves
• Seed if chewed

Amount Needed to be Consumed for Clinical Signs / Death:

• Green foliage is readily consumed and fatal at:
  • Monogastrics – 0.1% of an animal’s body weight
    • 1 lb plant material in a 1,000 lb horse
  • Ruminants – 0.5% of the animal’s body weight
    • 5 lbs plant material in a 1,000 lb cow

Inform friends and neighbors about the danger of yew. Don’t feed the trimmings to livestock!