animal flaps function the same as regular doors, except they allow pen animals to enter and leave. You could also use a regular door in addition to those. try checking food settings in a pen marker and allow all animals to eat everything, maybe there are some restrictions, also animals that are not kept in pens won't eat food in pen,. this rimworld how to make a pen guide will show you how to feed animals in a pen and how to make a big enough rimworld pen zone. support me by checking. i recommend you plant dandelions in the pens of animals. Not only does it look aesthetically quite pleasing, dandelions are really good at providing raw plant food.
