My dog, to whom I owe great hakarat hatov, has been diagnosed with both IBS-irritable bowel syndrome and chronic kidney failure. The vet says if she eats other than what I give her (special dog food that is chametz and kitniot snacks) it will accelerate her kidney failure and shorten her life. She will also have diarrhea.
Also I had planned on making the kitniot snacks for Pesach in a chametz pot because I have to use a blender. I do not have a kitniot blender for Pesach. My Rav is not capable of answering these 2 questions of what to do about the chametz dog food and whether I am allowed to make the kitniot snack before Pesach with chametz equipment. I live in Ramat Beit Shemesh. I am not dati leumi but not Israeli charedi either.
Of course, you cannot give the dog chametz food on Pesach. There is no problem in giving the dog kitniyot food. You can use the chametz blender for preparing the kiyniyot food. You can use the chametz blender before Peasch for this purpose, provided that the blender is clean and no actual chametz is present.
Good luck with the dog, and chag kasher vesameach!