Human feces is the most efficient as far as poo to weight ratio, it is 6x more effective than small animal poo, and the ratio gets worse as you go up in poo size. Use a whip to gather poo quickly from around your tames.
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!