Until they are adult all baby animal feedings give around 1-3 coin and 1 xp, except mule and horse which give 1 energy and 1 xp.
Found this chart by xRaptor on the Forums
*Please let me know if you have more info on these animals as this is a work in progress :)
You can collect a bonus from the chicken coop once per day, and what it does is click on all your chickens for you.
Make sure all your chickens are ready before you collect that bonus!
Adult chickens give you 3xp when you collect so it's pretty valuable to use this! You have to click FAST if you want to get those bonuses, although you could try using a popup screen to stop them from fading, maybe turn in a collection right before you collect and publish once you're done getting the bonuses.