So here's the thing. By mistake, and it's not the first time, i fed one batterfly with not only one unity of food but with ALL (Gave all 70 I had at once).
This could be easily solved if by default the option would be one and not all.
Batterflies will now only consume enough to get 100c worth of food at any 1 feeding, giving you 3 guano. This would be 20 planks, or 10 meat, or 2 cold tacos, or 1 awesome stew.
If you were trying to feed 3 planks at a time, this still ends up wasting 55 planks, but at least you don't loose 250.