Stacie wrote:

"Casein is a milk protein which is present in all milk, including human
milk.
It's not so much that "casein" is a problem for people, but *foreign* milk
proteins -from the milk of another species, that is. So, if the question is
whether goat's milk can be harmful to or intolerated by humans, the answer
is yes, it can be."

In my experience, the issue of the unsuitability of "foreign" protein is
raised with respect to non-native (not the right term I'm sure but you
understand) milk but not with respect to animal flesh itself. This has long
puzzled me - is anyone clear about why the protein in "foreign" animal flesh
might be less problematic?

David