After emptying his inventory space, Liam still always carried with him a lot of herbs, not just the essential ones.
Since he did not know when he might need what, he usually kept a stock of different items. Right now, he started taking out these things one after the other.
But he did not feed the herb to the egg because that would be impossible. The eggshell won't magically absorb the different herbs and such.
Luna would still need to consume the herbs on her own if these herbs were useful at all. Otherwise, the effect would not be there.
But that was not the only method. Liam knew another method.
In his slave days, the thing that he had spent most of his time on was plucking herbs in different places, maintaining the guild herb farms, watering them, and taking care of them.