No Yews for Cows
"The plant is exceptionally toxic, with one mouthful able to kill a horse or cow within 5 minutes. Toxicity is compounded by the apparent palatability of yew. Many animals are poisoned accidently when yew trimmings are thrown into the pasture or when yew is planted as an ornamental within browsing reach..."
Full article about English Yew, Japanese Yew (Taxus baccata, Taxus cuspidata) and livestock poisoning.
Wreaths are typically not made from yews. Although they are a common shrub planted where deer browsing is light, they are most usually sheared into hedge or topiary forms. Why yews kill cows and not deer is one of Nature's cruel jokes, as you have to put yews on the Do Not Grow list because deer seem to prefer them to other foods in winter when there is no garden to devastate.