So it looks as though food can be created without additional killing, and if Harry is willing to eat duplicates of preserved food (I can’t see any reason why not), then the proportion of killing to the amount of food can be driven very low.
Particularly given that magical healing would allows the collection of initial ‘food prototypes’ with no long term damage! (Although it would probably rule out things like hearts.)
This is one of the few cases where canon is very clear about how magic works: Gamp’s Law of Elemental Transfiguration.
So it looks as though food can be created without additional killing, and if Harry is willing to eat duplicates of preserved food (I can’t see any reason why not), then the proportion of killing to the amount of food can be driven very low.
Particularly given that magical healing would allows the collection of initial ‘food prototypes’ with no long term damage! (Although it would probably rule out things like hearts.)