I just want to add a few comments on some of the things you wrote
 
>I have never had a ferret that WON'T play with a mouse
 
I've never given my ferrets live prey but have seen them catch and kill
2 rats and a mouse that made the mistake of coming into the house.  Never
did they play with the rodent prior to killing it.  The speed of the
dispatch was amazing.  One canine to the base of the skull and it was all
over.
 
>The problem arises in getting an adult ferret to eat any kind of BARF or
>live diet.  I won't go into that headache.
 
BARF is not a suitable diet for ferrets.  It is ground, so no good for
preventing periodontal disease.  Some contains vegetables which a ferret
needs as much as it need carbs - not at all.
 
Small whole prey is an excellent diet for ferrets with raw meaty parts of
prey with occasional offal coming a close second.  Provides all of the
nutrients needed without the excess carbs and prevents dental problems -
in fact, can remove a moderate tartar build-up!
 
Changing ferrets to a good diet need not be a nightmare.  For people
who'd like to see their ferrets' eating habits change, the folks at
Natural Ferrets can guide you through each stage.
 
>...and that an active mind is a contributing factor in the longevity of
>a ferret.
 
I couldn't agree more.  Another reason why I think that ferrets should
not be confined to a cage.
 
>...an even older geezer, as today [the 28th] I have to endure another
>addition of a year to my age...."
 
Happy Birthday!
 
>My question is (And I *DON'T* know the answer!) how does one know that
>pre-killed' mice are killed humanely?  How are they killed?  Vacuum
>chamber, electric shock, freezing, or even the use of some sort of
>lethal gas, which, of course, questions how good the pre-killed mice
>would be for any animal, if this is the means of displacement!"
 
Mice & chicks from reputable suppliers are killed by carbon dioxide gas.
It is not a poison but replaces the oxygen in the air.  The animals lapse
into unconsciousness within seconds, without feeling short of air, and
die soon afterwards, making them safe for other animals to eat.
 
Cheers
Shirley
[Posted in FML issue 5197]