If you go to http://www.herringlab.com/photos/ you will see a ferret
struvite stone in the 4th column, 4th row.  Struvite stones
(MgNH4PO4-2H2O) are the ones from too much vegetable matter in the diet
with which the urinary pH goes too alkaline.  It has cystine stones
(SCH2CH(NH2)-COOH)2, but I don't recall offhand that it shows ferret
cystine stones among them.  You can see what they can look like from
Brenda's site, though, where she posted photos of the ones that took her
little one from her.  Cystine stones are the ones that call for a person
to reduce the protein intake and are associated with urine that is too
acidic.  I have heard of three or 4 stone types in ferrets so far, but
the other types are very rare.  One involved a rare liver problem and I
got the treating vet in touch with two vet urolith specialists (having
corresponded with several when Hilly was so very ill so at the time I
could call up their contact info easily) but never heard how that ferret
resolved.
 
You know, the fact of the matter is that the disagreements here don't
matter, and who wants cystine stones to not occur doesn't matter.  No
one who finds that his or her desire based upon discussion -- i.e. solely
for the sake of argument -- that there are not cystine stones in ferrets
has anywhere near as much to lose as people whose ferrets have already
died, or already suffered kidney damage, or already had to have major
surgery just to survive due to cystine stones.  What is the "pain" of
"losing" something as frivolous as a disagreement compared to that sort
of loss?  You want to know pain?  Those of us who have encountered these
stones know it, and mine is nothing compared to those who lost their
little darlings.
 
And no one here could ever wish more that there are not cystine stones
than someone who has buried a ferret due to cystine stones.
 
Does that mean that others should not try high protein diets.  No, of
course, it doesn't.
 
Some of them are pretty well thrown together and say squat on their sites
about the important details like how much of their protein comes from
animal sources and how much from plant sources, or what their fatty acid
details are -- and frankly I think that anyone should be wary in that
type of situation.  BTW, according to my stored notes from veterinary
nutritional experts one pet food trick used by some places when the
amount of vegetable protein sources is increased in food for members of
Carnivora is to decrease the amount of fat.  Unlike humans, members of
carnivora have a tendency toward getting fat on foods with more vegetable
protein -- they eat and eat -- so the manufacturers who want to save
money by making worse food (cheaper for them so more profit) decrease
fat to not be as associated with obesity.
 
Other manufacturers will have involved careful development.  For
instance, I know that years of extremely careful work went into the
development of the exemplary Pretty Bird food.  If we didn't have two
ferrets who get cystine stones we'd be inclined toward that particular
food.  It was not thrown together for a fast buck just to join what may
or may not be either a fad or a way to protect ferrets from insulinoma.
Instead there were years and years or trials and perfecting that went
into developing that food.  If you are going to feed high protein that
is the food I would personally recommend.  You can get all the important
types of details from them, too, and their website is not
self-contradictory.  I have found them to be honest and forthright.  For
them I have high respect.
 
If we were in the position where we would again consider feeding a high
protein food what would I do differently?  I would know that discomfort,
urinary spotting, and constipation (from pressure against the colon) are
all possible signs of a serious urinary cystine stone problem in a ferret
who personally can't handle high protein levels safely.  If I were
feeding such a food I WOULD GET URINARY pH STRIPS AND CHECK THE FERRETS'
URINES pretty regularly!  That is a biggie for increasing safety on this
score since you will often see acidic urine in the vulnerable ferrets
when they are in a high protein diet, and IT IS REALLY, REALLY CHEAP TO
DO.  Have your vet or vet tech show you tricks for getting urine.  If the
urine pH was low I would get to the vet right away to image the urinary
tract and to test, and I would immediately stop feeding that individual
a high protein diet.  See the section just above the blood values in
http://miamiferret.org/fhc/ physiology.htm
 
The thing about a high protein diet is that if an intriguing hypothesis
pans out (at this point it is highly hypothetical but that doesn't mean
that it will or will not pan out -- it just means that it is too early to
know, just as it is too early to know many important details of cystine
stones in ferrets) then it might be possible to decrease insulinoma
rates.  One thing which complicates measuring that is that there is no
baseline measurement of insulinoma rates.
 
Personally, in 24 years with ferrets the insulinoma rate in our family
has been low (so has the adrenal growth rate here but at least now we
have some decent data indicating that our care in almost always providing
a lot of places with complete darkness may account for seeing so few
adrenal growths in our ferrets -- in fact the ones that did occur
happened soon after we for some reason did not or could not provide as
much complete darkness such as the year when I could barely walk).  Why
has the insulinoma rate been low in our family?  It beats me.  I haven't
got a clue (but have had good reasons to discount some hypotheses people
have sent me over the years).  All that I know is that if you also
combine them with the ones here who had lymphoma/lymphosarcoma in the
pancreas and the one who had carcinoma in the pancreas (just in case
there might also have been insulinoma present) our family rate still is
barely 20%, and one of those came to us at an advanced age.  So, for us,
there is not as much emotional pressure to try high protein diets as
would be felt by someone who had a lot of ferrets with insulinoma.
 
Insulinoma can also be a heartbreaker, so I fully understand exactly
why people want to try high protein, low carb diets in hopes that they
might decrease the rate of insulinoma.
 
What I think will eventually happen is that we all will wind up with diet
options that are optimized for specific needs when ferret individuals are
fed alone -- and maybe some base foods to give when all are eating
together so that we can do some dietary shaping for individual needs.
[Posted in FML issue 4904]