Plants in the Bible generally represent facts, knowledge that can be gleaned from the world. Plants that can serve animals as food represent facts that have the potential to be put to use, ones that can lead to something good. A pasture, then, is an area that offers a great deal of this sort of useful, life-building knowledge. "Pasture" is often used as a verb in the Bible as well; to pasture animals means teaching people facts that can help them do what is good in life.
Jeremiah 51:20-23
20
You are my battle axe and weapons of war: and with you will I break in pieces the nations; and with you will I destroy kingdoms;
21
and with you will I break in pieces the horse and his rider;
22
and with you will I break in pieces the chariot and him who rides therein; and with you will I break in pieces man and woman; and with you will I break in pieces the old man and the youth; and with you will I break in pieces the young man and the virgin;
23
and with you will I break in pieces the shepherd and his flock; and with you will I break in pieces the farmer and his yoke [of oxen]; and with you will I break in pieces governors and deputies.
