Once again, it is forbidden to own chomets. Feeding the chomets to an animal you do not own for the pleasure of doing so,
may possibly be called having benefit from the chomets.
but you can’t buy it in the first place, so feeding it to the animals may be a SECOND averah. I know you mean well, unlike some of the posters here, but you are just clouding a very simple issue.”
Ok, so let’s look at it from a strictly practical POV. Do you really want to risk getting grains of chametz on your clothing and hands on Pesach, even if it does NOT belong to you (and if it doesn’t, then by what right do you feed it to an animal that likewise does not belong to you?), and further risk bringing it into your Pesachdig home?
We are not allowed to buy chametz that was unsold by its Jewish owner (chometz she-avar alav haPesach) even after Pesach. So why do you think it would be permissible to use mamesh chametz ON Pesach, even if it belonged to a non-Jew? (If my logic is faulty, sorry, it just is coming into my head this way – too many cleaning fumes, I guess).
Bottom line – I wouldn’t want to take the chance of bringing even a dot of chametz into my home. Unless you are covered from head to toe in a disposable burka, it is very possible you will have chametz on your person SOMEWHERE.