It's it the avocado flesh itself that's toxic or just the skin and pits? I've heard both and also that someone's chickens also had no ill affects fron eating the flesh of avocados from a neighbour's tree which used to drop them into his yard. They wouldn't eat the skins or pits though.

I hope you'll keep us updated with how you go. It would be great if you could manage to forgo the commercial feed completely.