Photo by Sue Weaver
I love to eat oak leaves! Yum!
You know how much we goats love yummy acorns, but did you know oak leaves are us goats’ favorite summer treat? That worried Mom for a long time because many toxic-plant lists say oak is poisonous.
Every day when the does and wethers go out to browse, they rush down the ridge to nibble leaves and twigs from oak sprouts (what Ozark people call little oak saplings) that pop up in our pastures each year. Dad buzzes them off with the tractor and bush hog, but they grow back up by next spring. Uzzi and I make a beeline for the oaks in our yard after storms. The wind brings down lots of yummy leaves!
Mom started searching for oak information online. Did you know there are more than 600 species of oak around the world? In some countries people cut oak boughs for animal feed. She learned that in a British research paper by the Natural Resources Institute called “Use of Trees by Livestock.” The “Quercus” chapter (quercus is Latin for oak) says cattle, sheep, goats, horses, and pigs all eat oak leaves and acorns. Wild animals like deer and elk like them, too.
Oak toxicity happens when we consume too high a proportion of oak leaves or acorns in our diets. That’s because oak contains a compound called phenol, which includes tannins. This compound is toxic in large amounts. The leaves and acorns from some species contain more tannins than others. Green acorns contain 1½ to 3 times more tannins than ripe acorns and new spring leaves and winter buds have more phenol in them than mature oak leaves.
Studies show that pigs and goats show the greatest tolerance to oak toxicity and cattle and buffalo the least; sheep and horses fall midway between. In all species, young animals are more susceptible to oak poisoning than grown-ups, like Uzzi and me.
In Europe, leaves and twigs from some species, like holm oak trees found in the Mediterranean region, are used as a protein supplement for goats. In India and Nepal, dried oak is a major source of livestock feed.
The trick, Mom learned, is feeding oak in moderation as a very small part of our diet (think: as a treat) and in choosing mature leaves and acorns over early spring growth and unripe acorns. Red and black oak varieties contain the most tannins; white oak varieties contain the least. If you’re not sure, break open a mature acorn and taste the nut. If it’s so bitter that it makes your mouth pucker, it’s chock full of tannins; if it’s sweet, there are fewer tannins. Many species of acorns can be eaten raw by animals and humans, but others require that the tannins be leached from the nut.
Don’t let any kind of livestock except for swine eat their fill of yummy acorns. Some horses, for example, obsess on acorns and pig out; this can lead to painful, crippling laminitis. And cows that consume oak leaves and acorns for more than 75 percent of their diet are prone to potentially fatal oak poisoning. Even as much as half their diet from oak leaves and acorns leads to oak poisoning symptoms. According to the University of Arkansas, symptoms include lack of appetite, constipation, diarrhea (which may contain blood) and kidney failure.
The bottom line: Mom is bringing Uzzi and me two big branches of mature oak leaves every day. Yay, we love it! And Mom isn’t worried about us getting poisoned any more.