Shalom Rabbi, could you please say what is the source in halacha that states that it is forbidden to feed our animals chametz on Pesach?
One is not allowed to own chametz that can be eaten by an animal, i.e. a dog. Dog food is included, as by definition it can be eaten by a dog. (Shulchan Aruch O:CH 442:2 and Mishna Berura 442:10.
In addition, one is not allowed to feed chametz to an animal, even if the animal does not belong to themselves. (Shulchan Aruch O:CH 448:6, Mishna Berura ibid:28, and Sha’ar Hatzion ibid:76)
All the best