Pets and Hametz

Question

If the definition of hametz is rauy le-akhilat kelev, it would seem that if there is hametz in dog food, it is absolutely forbidden. And yet with regard to the pet food discussed you said that it was no no good for people but OK for animals, but that since this was a sensitive topic you were reluctant to explain it. I am missing something here, because if it's OK for animals, and you can keep it in your possession on Pesah, then it isn't hametz. But since the dog food contained oat groats and brewers dried yeast I wonder how it is not hametz and what halakhic leniencies you were reluctant to explain before Pesah.