Should I let my animals consume any part of the yew plant?

Horses, Sheep January 04, 2012 Print Friendly and PDF

No. This is a deadly poison. Because of the extreme toxicity of the yew plant and yew parts, under no circumstance should livestock animals (horses and other livestock) be allowed access. Yew can be toxic to horses at a very low rate. For a 1,000-pound horse this could be less than one ounce. All parts of the plant are toxic. A few licks of the leaves or needles could kill. The first notice that you have a problem would be a dead horse. Horses, which do seem to have some desire to consume the yew plant, may drop dead immediately after consumption. The toxin affects the central nervous system, and the cause of death is essentially massive cardiac failure. One of the toxins is an alkaloid called taxine. The plants contain a variety of other potential toxins including cyanogenic glycosides and ephedrine. It is toxic to ruminants, but probably at higher levels than for horses. Most yew varieties also contain taxol. Taxol has been used as an anti-cancer chemotherapy drug. Interestingly, although toxic to domestic ruminants, the yew is not toxic to wild ruminants such as moose and deer. Please see the following links for more information:

Cornell University Poisonous Plants Database

USDA ARS Poisonous Plant Research Laboratory