Chins and Rabbits can just be fed woad leaves. And spiders can be fed raw bird meat. They don't eat enough for even IM to not keep them topped up if you have access to Oo'glog.
The only reason to do chickens over chins is if you're an IM I guess, or if you need the achievement, but they can just be fed fruits or veggies with a higher buy limit too.
Or buy sunchoke or flytrap seeds. Or literally any type seed - they eat once per animal per hour. Even in an entire 24 hours, your small pens will only go through 192 seeds each. Even at the 100 limit seeds, you can buy 600 each a day.
Would be nice for them to up the limits but it's not strictly necessary.