In TS4, the Cowplants gets hungry about every 12 hours. If it isn't fed, it will put out the cake. The Sims will try to eat the cake if they are hungry. They will get eaten and spit out. They will have a "Drained" moodlet for two days. The Cowplant will have a large udder, and need to be milked before it will put out the cake again if it is hungry. When your Sim milks it, they will get a glass of "milk" "flavored" with whatever emotion the Sim who got eaten. If a Sim drinks the milk, they will get that emotion. If the drained Sim tries to eat the cake again before their moodlet is gone, they will get eaten, and will die. The quickest way to remove the Drained moodlet is to simply drink the "glass of emotion", and they will get that emotion instead of being Drained. Your Cowplant will die if it gets too hungry, usually some time after 12 hours. I have never had a Sim die if they had low needs, unless they were also Drained. Their hygiene will be low after being eaten, but that is because they were eaten, and it's icky inside a Cowplant. :p