Since you were helping care for them, maybe post what he was feeding them? Diet can change meat flavor a lot.
What about the
water, was that highly mineral/metallic?
Do you know if he was giving them supplements?
Another and likely possibility is the butchering of the animal. Often times that can change the flavor drastically depending on how it is done. A metallic flavor sounds sort of like too much blood in the carcass. That can give it an iron flavor.
Or of
course if the dispatch was botched and the animal stressed it could be an adrenaline taint. Though it doesn't sound like that to me. Though it has been a long time since I have had adrenaline tainted meat, so could be wrong there.
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