For her hypothesis to be accurate there are three different scenarios:

1. Different pieces of a kibble brand would have to emphasize different
nutrients, and mixing with others would have to somehow change the
proportion of those pieces (which does not make sense since they would
be in the same proportion to each other, just with others mixed in).
Do you know of any (or many?) ferret food brands which actually mix
pieces that emphasize different nutrients in different pieces? If her
hypothesis is correct then picky eaters who refuse certain pieces of a
kibble would also have nutritional problems even when fed just one type
of kibble and for those ferrets it probably would make sense to go to
kibbles that have the range of nutrients in each piece.

2. Specialty foods which use different proportions (like senior foods,
or kit foods, or kidney disease foods) mixed with other foods would
result in a nutritional profile that was between the two food types.
For some this may be good but for others it might defeat the purpose,
though the specialty foods might need to be introduced this way.

3. A good food mixed with a crummy one would be better than the bad
one but not as good as the good one.

For ferrets there can be several reasons to blend foods:

A. Ferrets are hard to introduce to new foods so blending gives options
for when it is hard or impossible to get the preferred food.

B. It allows transitioning to new foods, or inclusion of multiple foods
in the diet.

C. If a ferret needs a special diet for health reasons, like when
feeding ferrets who are prone to cystine uroliths a diet of no more
than 35% protein it gives more control.

D. It gives variety and sensory stimulation.

If you would like to read nutritional information from an actual expert
I suggest this site by someone who has doctorates in both veterinary
medicine and veterinary nutrition:

http://www.petdiets.com/

Oh, and it pays for people to have this ref handy, too:

http://www.accessdata.fda.gov/scripts/newpetfoodrecalls/

and if feeding homemade or nearly so then also these:

http://www.fsis.usda.gov/FSIS_Recalls/index.asp

http://www.fda.gov/Safety/Recalls/default.htm

http://www.fda.gov/downloads/AnimalVeterinary/GuidanceComplianceEnforcement/GuidanceforIndustry/UCM052662.pdf

http://www.fda.gov/AnimalVeterinary/NewsEvents/FDAVeterinarianNewsletter/ucm093853.htm

(but remember with that that ferrets do well on more Vitamin A than had
first been realized) and that this is useful ref in many ways:

http://jn.nutrition.org/content/137/8/1916.long

There are certainly there are many others. Danee DeVore had an
interesting article in Ferrets Magazine in the past, for example.

If you go to

http://www.smallanimalchannel.com/ferrets-magazine/default.aspx

and put 

ferret food

in the search box you will find multiple things that you can read.

For some food dangers use these:

http://www.smallanimalchannel.com/ferrets/ferret-health/poison-prevention.aspx

http://www.aspca.org/pet-care/poison-control/

and if you look long enough maybe Danee's article is there, too.
Personally, I'd like to see the veterinary article on raisin poisoning
in ferrets which had been in print form on the site, too, but so far
have not found it there.

Sukie (not a vet)

Recommended ferret health links:
http://pets.groups.yahoo.com/group/ferrethealth/
http://ferrethealth.org/archive/
http://www.afip.org/ferrets/index.html
http://www.miamiferret.org/
http://www.ferrethealth.msu.edu/
http://www.ferretcongress.org/
http://www.trifl.org/index.shtml
http://homepage.mac.com/sukie/sukiesferretlinks.html
all ferret topics:
http://listserv.ferretmailinglist.org/archives/ferret-search.html

"All hail the procrastinators for they shall rule the world tomorrow."
(2010, Steve Crandall)
On change for its own sake: "You can go really fast if you just jump
off the cliff." (2010, Steve Crandall)

[Posted in FML 7116]