Why vegan? Why not feed them eggs and breast milk? Even cow milk? Cows don't care if you get milk from them. They make unlimited amount of milk as long as they are stroked.
Most eggs are not fertilized; birds (hens, ducks, etc) lay eggs even if they're not fertilized. What happens to them? The eggs rot. Totally a waste of perfectly edible food rich in many nutrients. If you feed birds with flaxseed, they produce eggs with more omega-3 which improves brain function.
There's no cruelty in it whatsoever.
