“Grass” is the tongue in cheek smart aleck answer, but the real answer could take a Botanist to explain. Here’s something in between.

Depending on the area of the country they are raised, there are cool season grasses and/or warm season grasses. Some of the familiar cool grasses are bluegrass, fescue, ryegrass, orchard grass, and annual cropped grasses such as wheat, barley, and rye.

Some familiar warm season grasses are bermuda grass, switchgrass, buffalo grass, bluestems, and a host of other prairie grasses plus the cropped grasses such as corn, sorghum, and millet. Cows also love to eat the “weedy” grasses such as quackgrass and crabgrass.

A very important part of a cow’s diet is legumes which usually have higher protein content than grasses. Things such as alfalfa, clover, trefoil, lespedeza, peas, and beans fall in this category. Then there is the category of forbs, many of which are considered weeds. There are many of these such as kochia, pigweed, bindweed, but also turnips, radishes, carrots, kale, and many others. Cows will also eat the leaves and small stems of woody plants like shrubs and trees. In the winter, many cattle are fed hay or silage made from the above plants.