Make a circle of Lystros. Put beetle(s) inside circle. Pet Lystros, feed beetle(s), store fertilizer in Lystro inventory. 300 per Lystro, no cage/fences needed. (Set follow to lowest and whistle one at a time to arrange Lystros.)
Get yourselves a Phiomia as well! Feed it stimberries and you'll have plenty of medium feces to throw in the dung beetle. Fill it up, and come back and watch more fertilizer than you can imagine. I'll never use compost bins again!