Regular readers will know that I have always maintained an uncomfortable position on the term “grass fed beef.” It’s not that I’m against it; I’m all for it and firmly believe that it is one of the healthiest and most environmentally responsible foods. But the word “grass” was an inadequate choice, because there is no environment in the world where cattle are only eating grass. They are herbivores, and they do best when they have a variety of leafy plants in their diets, grasses being just one constituent. But beyond leafy greens, we should recognize that cattle also need some stemmy, stalky, and woody plants.

This week I spent a few afternoons cutting dead and dying trees out of the hedgerows. Since the cattle were nearby, I tossed chunks of bark and branch tips over the fence for them. They stood around, happily munching on tree bark, and gossiping among themselves.

If I were a goat farmer (perish the thought!) I’d have even more to say about eating brush, branches, and vines. Of all domesticated livestock, the preferred diet of goats is the most biased toward woody plants. But cattle and sheep also thrive when they can nibble branch tips and chew the bark from trees. This is a subject requiring much more investigation because of the thousands of nutritional compounds found across the entire array of plant species in any landscape, but we know enough to state that the various plants in our farm all have value to the cattle as food or as medicine.

Probably the most well-studied of these compounds found in woody plants are tannins. This group covers a wide array of separate compounds, and as we learn more we’re finding that different tannins fill different nutritional roles, so I’m forced to generalize here. Tannins are the chemicals that make the mouth-puckering taste associated with acorns, dry red wine, and tea. Plants produce them as a defensive measure against insects and bacteria, so they seem to be in some sense anti-nutritional. But large plant eaters have digestive systems adapted to thriving on tannin-rich plants. The current state of research for cattle suggests the following three major benefits from tannin consumption:

1. Tannins help stabilize high-alkaloid grasses to make them more digestible for cattle. Our farm has some heavy stands of reed canarygrass, a wonderfully productive grass in the early season, but later in the year the alkaloid levels spike making it unpalatable to our cattle. However, if they are able to browse tannin-rich tree branch tips, they can continue to graze the reed canarygrass through the entire growing season.
2. Some proteins become degraded in cattle rumens (the first stomach) and aren’t able to be used by the time they pass into the intestine. Tannins can bind to these proteins, causing them to pass through the stomachs unscathed and on into the intestines for hindgut absorption.
3. Cattle have been observed to seek out high doses of tannins when they feel themselves sick or suffering from high levels of parasites.

I can’t pretend to know what specific benefits the cattle get from each particular plant on the farm. But I work from the assumption that more plant diversity is always a better thing, and that our livestock have sufficiently well-tuned feedback loops from their digestive systems to their brains to allow them to select their food. So my role as a farmer is to create an abundant edible foodscape on the farm, giving the cattle the richest, most varied diet possible. In the winter, when we’re feeding them stored pasture plants we mowed last summer, I’ll keep serving up bark and branches as side dishes.