What is the ruling on slaughtering donkeys to feed animals in the zoo?

It is not permissible to kill animals needlessly, except for those that are harmful, or whose killing or slaughter for food has been permitted by the Shariah.

It has been narrated that killing ants, shrikes, and frogs is prohibited. It has also been narrated that whoever kills a sparrow needlessly will be questioned about it on the Day of Judgment.

It is not permissible to slaughter animals to feed other animals if there is no valid purpose or recognized benefit in doing so, especially if an alternative food source is available.