I was asked:
>Something that makes no sense to me is ferrets suffering from a diet
>too high in protein. Ferrets are obligate carnivores - how can too
>much protein in general be an issue?

I put the math in below but am adding this paragraph as a summary and
a "prepeat" having written the rest first, if I may coin a word, In
summary, obligate carnivores are called that because their bodies can
not do things like some amino acid conversions we do so they need
animal food sources. The sources I have read have obligate carnivores
who are also hypercarnivores typically eating about (or in a few cases
"at least" depending on species) 70% animal food sources by Calories. I
recall a figure that mice and a number of other animal bodies ingested
are 50% Calories protein plus or minus several percent. 50% is half.
Half of the 70% from animal sources for obligate hypercarnivores is 35%
protein minimum. So, many of the high protein foods which give over 35%
protein are already well into the high side with an attempt to give
what would be eaten if ONLY animal sources were consumed. That is for
hypercarnivores. Not all obligate carnivores may be hypercarnivores
(though most might be), but all obligate carnivores do have much higher
demands for animal sources of food than the rest of us. Fudge words are
there due to gaps in research which may be filled later, especially
with more intestinal microbiome and genetic work.

The tendency to form cystine stones is a genetic variation which makes
the kidneys unable to deal with four of the amino acids. So, they are
VULNERABLE to too high levels of protein. Notice that the ones we had
who survived cystine stones and lived full lives MET the 35% animal
protein levels but did not go enough above to trigger their problem.
When that is not sufficient for some ferrets then adding meds rather
than taking diets much lower is probably preferable.

Now you have had the summary of obligate carnivore and the summary of
the cystine stone variation so can read further OR skip to the final
two short paragraphs. In the paragraphs between I give some details.

Amino acids are the building blocks of protein.

The term "obligate carnivore" is one that can cause confusion. It does
NOT mean that only animal foods can be eaten, or even that only animal
foods can be digested, and in fact even polecats will ingest some
non-animal source things.

What it means is that animal source foods MUST be part of the diet
because of certain nutrients like some amino acid needs which can not
be met for that species by other sources and can not be produced by
their own bodies. Obligate carnivores tend to have more essential amino
acids than we do, as I recall, because their bodies can not convert as
many amino acids as well as we do.

Animals which are the most dependent obligate carnivores -- like the
big cats -- typically need about 70% of their diet to be from animal
sources and are called hypercarnivores. Note that is NOT 70% protein.
Many whole animals are about half protein by weight, not just mice,
if memory serves me. I will have to look this stuff up and post refs
later but will definitely need an eye rest between.

It might be that many ferrets may do fine on less than 50% protein and
in our experience is that often has been the case.

So, 50% (animal cadaver percentage which is protein) of 70% (the
percentage of animal source food by obligate carnivores in the wild)
gets you 35% protein on such wild diets which I seem to recall is where
the 35% in the original ferret foods comes from. It probably should be
seen as a safe minimum for animal protein sources for them until more
is known. Safe maximum for ferrets is yet another question that remains
unreasearched.

We have regularly had eight and nine PLUS year old ferrets who always
lived on on 35% animal protein. That percentage was what was normally
provided back before fancies were bred much.

Ferrets have apparently had more genetic burdens since fancies became
popular and were bred more. Does that change food needs or cause more
variation among ferrets for food needs? No one knows.

We have had ferrets in our family for over 30 years, I guess 33 now,
and in the past it was absolutely normal to have ferrets last and
average of seven and a half years so many people had had ferrets who
were 8, 9, 10, and sometimes older, many of which were still quite
active. There were no high protein kibble foods back then unless
homemade or home provided.

Oh, and an important note for those providing chicks or newborn mice
from pet stores: those have different mineral content percentages than
adult anImals, most noticeably being too low in calcium.

But, again, before so many ferrets included fancy ancestors or were
fancies themselves there apparently were fewer genetic burdens, and
reports on the early internet and in the interest groups in its
predecessors had very few mentions of symptoms of some current medical
problems often discussed (like heart disease, insulinoma and adrenal
disease), but what seemed like a far higher percentages of some others
(like lymphoma and ruptured spleens), as well as pretty much no one
saying that anything under late sixth year old is old for ferrets. Some
of that impression could be selective memory, some could be changes in
medical care as is certainly the case for decrease in ruptured spleens,
but some may represent genetic population changes in pet ferrets
between then and now, population genetic shifts through breeding
selections. In fact, you can look through the Ferret Mailing List
Archives and find that reports of adrenal disease and adrenal symptoms
before the ages of five or six years apparently increased substantially
in rate over time. Many who have been around a long while have noticed
that.

Plant sources of much protein are NOT right for ferrets in too large
amounts for other reasons. For example, we know that pretty much any
ferret with too much of their dietary protein sourced from plant
sources will get a different type of urinary stone, struvite stones.
Those are the most common urinary stones found in pet ferrets, and
also can be caused by infections.

Again: 70% of the diet from animal sources does NOT mean that their
diets are 70% protein. Whole animals are NOT all protein. A mouse,
for example is something like 50% protein. I can not recall the exact
actual average percentage but seem to recall it is something like a
few percentage points below or above half protein, which is why high
protein kibbles aim for that range, but that assumes nothing other
than animals is eaten, which is usually not accurate for animals who
are hypercarnivores in the wild.

50% of 70% is 35%

She added this excellent point: > They aren't 100% positive it is the
peas but they are researching it and are >starting to believe peas are
the cause.

It would be interesting if they find out if the mechanism postulated by
that British biochemist is accurate, that is the hypothesis in which
the combination facilitated by high sulphur intake of high methionine
intake might bioconvert to cystine. If so then there are OTHER foods
and OTHER food combinations which may need to be avoided in ferret
diets because the same two potential problem ingredients would be in
too high amounts. The MECHANISM which may be involved REALLY needs to
be researched and explained. Looking at just peas would give only a
suggestion but then the same problem could happen with other sources of
the problem ingredients, no matter what the mechanism is. Looking ONLY
at peas as a possible problem would be only a starting point, albeit,
one that can help. Knowing the mechanism involved would be the gold
standard.

[Posted in FML 7972]