Grass like a tree, stores nutrients all winter, it is the Spring grass that is our best medicine, the spring butter is proof of this, it can be seen by the color and taste as well as the benefits. So those that eat the grass is getting far more than eating the cow that ate the grass first.
When I was a kid my parents told me the grass and just about all the wild berries were poison. Now I know most all the flowers can be our food and much in the woods can be eaten.