Core dry for cats?

[catmom5]

A bit of a complicated situation here ~ five cats, one who had ARF in November.  She has since had surgery for bacterial peritonitis, possibly because of one kidney that was badly diseased.  Anyway, when she came home from the hospital (live near a major vet teaching hospital) the vet put her on Eukanuba Rx because of IBD, ARF.  I had been giving my other cats California Natural Chicken/Rice dry, but lately they have not been eating very enthusiastically.
Decided to try the Wellness Core because it's grain free and the phosphorus is actually lower (dry weight calculations) than either the Cal Nat or Eukanuba (which I HATE feeding).  Also have noticed a bit more water consumption, not sure whether it really is or whether I'm just paying more attention.  It's hard to tell because I have fountains for them.
Anyway, has anyone had any experience with Core Dry?  I like the ingredients, don't like that they use MF, but I'm running out of good options here.  My cats will only eat FF wet and that's not even a choice!
Any thoughts?
Thanks

[catmom5]

The Wellness goes back to the store ~ phosphorus is WAY TOO high for my ARF girl. 

[Sharon L.]

Higher phosphorus/magnesium and calories levels are something that all the grain free varieties seem to have in common. I feed my kitties far less of the Wellness than I did of other foods because of the calorie issue so I'm hoping that even with the higher phosphorus/magnetism levels they are getting a comparably lower or equal amount than what they ate in the past.

Sharon

[jenny]

I found a link to a study that found high levels of magnesium were pretty much washed out of the cats system when they ate food with a moisture level of 80 %.  Most canned foods are around 78 %, including Wellness.  Even so, Wellness is at very good levels of .02 - .025 for their foods.

Regarding the numbers for phosphorus, I also have them converted to dry matter so you can compare between brands. Turkey for example is 1.04 % on a dry matter basis, and with Janet & Binky's calculator I came up with  200 mg/100 kcal using the 'as fed' information from Wellness (i.e. not gauranteed analysis).

[catmom5]

Phosphorus levels should be kept below 1 if at all possible. (That's dry matter basis)