Actually, the Nutro one I used was their Natural Choice Line - which actually further proves what I was saying.  It's not only a specialty store brand, it's the "premium" version!

 

They have to add the vit-mn premixes, especially in kibble because these almost universally use "meals" in their formulations (canned depend on fresh or frozen meat sources mostly).  The Meals like "Chicken meal" have already been subjected to high temperutres in the rendering plant, causing the raw ingredients to lose nutrients.  Then the meal is further processed into petfood, subjecting it to more heat and thus causing it to lose even more nutrients.  So they need to "return" these nutrients in the form of vit-min premixes.  These are usually mixed according to the petfood manufacturers' proprietory formulations - and almost every Petfood manufacturer has its own philosophy on what constitutues an optimum diet for a dog or a cat.  Add to this the fact that other ingredients in any given diet affects the bioavailability of the nutrients in the food and you end up with...  a guessing game of how much to put back into the darned kibble!

The cat and dog nutrient profiles can also be problematic because both the NRC and AAFCO values have built-in overages to take into account the wide variety in cat and dog breeds, ages, life-styles (kitten, lactating, senior, working, sporting, toy, etc).   And it is difficult to put in maximum limits without more research. 

Salt is a necessary mineral, but the amounts found in some of the pfpsa tested foods is definitely excessive in my opinion.

The human requirement for sodium is 500mg per day - although according to Wikipedia the average well-seasoned diet contains about 5000mg of sodium.

According to Colorado State University the recommended sodium intake is 1,500mg daily with a recommended maximum of 2,300.

Sodium requirements for cats are even more confusing.  The recommended minimum daily intake is 40 to 60 mg/100g (400 to 600mg/kg) and yet kitten requirements are 1,500mg/day.  Seems high, no? (these numbers come from the NRC)

Confusing...

Also, there are studies showing that sodium intake not only does not have the same hypertension effects on dogs and cats as it does on humans, but sodium is also used to increase urinary output and decrease chances of crystals and stones.

However, cats with renal failure are advised to severely restrict sodium intake.  Could the high sodium intake we're seeing here be one of the causes of CRF?

6,444 mg/kg seems awfully high for a ten pound kitty.

Interesting, 5Pitas.  Disappointing response, to say the least.

European Union recommends a feline growth Ca:P ratio of 0.65-2.0 and a maintenance ratio of 0.65-1.5

I honestly don't know how to convert this.  Help?   

This website : http://cats.kenanderson.net/html/feline_nutrition.html

Says the following:

Proper bone development and maintenance requires a calcium to phosphorus ratio of O.9:1 to 1.2:1 for cats. Changes in this ratio can result in soft bones or in soft tissue calcification.

Wellness Indoor ratio = approximately 1:1, so it seems within range. 

Forgive me, I'm much more familiar with canine requirements.

Incidentally, the remainder of the ratios:

Nutro Natural Choice - 1.58:1
Indoor Natural Choice - 1.36:1
Nutro Max Cat Adult - 1.4:1
Purina Cat Chow - 1.15:1
Recalled Max Cat - 1.27:1

Now, that makes a bit more sense, no?  Once again, if the reference ratio is correct, Nutro appears to be higher than recommended.

Surprised?   

Can you explain, Cato?

Thanks, Cato.

Here is what I found.

"Growing Kittens Require Less Dietary Calcium Than Current Allowances
http://jn.nutrition.org/cgi/content/full/129/9/1698

These results indicate that the calcium requirement of growing kittens is not >6.0 g/kg diet, (calculated metabolizable energy ~20 kJ/g) and that kittens are not very sensitive to inverse Ca:P ratios up to 1:1.55.


Nutrient Requirement of Cats - National Research Council
http://books.google.ca/books?id=lXdN6yMaEJQC&pg=PA15&lpg=PA15&dq=nrc+calcium+ratio+feline&source=bl&ots=sUHCtfJLEF&sig=mQ7j1TcA99pv0wSvSjW66hlTO-U&hl=en&ei=0thDSo2MEcXJtge7oJCnAQ&sa=X&oi=book_result&ct=result&resnum=2

The ratio of calcium to phosphorus is important in both absorption and utilization of these minerals when one or both are near their requirement.  Scott and Scott (1967) have shown optimal utilization by the cat when dietary calcium:phosphorus ratios ranged between 0.9:1 to 1.1:1

After some more research I did find numbers that also pointed towards a range of 1.1:1 - 2:1 as acceptable, although the upper end of that ratio still seems high to me. 

In fact, given the findings above and the findings suggesting otherwise, it is my impression that this is yet another recommendation that has not been properly investigated.

I'm awfully sensitive to the Ca:P ratio, seeing the widespread incidences of crystals, stones, bladder infections and kidney failure.  Given that most of these companies do not conduct regular feeding trials, I'm a little wary of any number that seems excessive - particularly when you consider their "more is better" and "above all else - don't UNDER supplement" mantras.

Perhaps we should sound an organized call for more testing specifically on cats.  The Winn Feline Foundation is doing quite a bit of wonderful work... but it's not enough.  Why must this be so damn confusing??

I like your lake analogy, Cato.

I agree with you as well - when human nutrition is concerned, I'm very anti-nutritionism.  I'm a big believer in whole foods (not to mention local, and organic whenever possible). 

The same goes when homecooking and feeding raw to my own furkids. 

However, when dealing with processed foods... well, there's not much choice, is there?  There are several brands that are unable to claim "100% complete and balanced" because they don't meet AAFCO standards, and yet claim off-label to be a nutritionally satisfactory diet (Mulligan Stew comes to mind).  Problem with this is, if you have any long-term issues, they have clearly written on the label that their food is not meant to be a full meal and is to be fed on an intermittent basis only. 

How does one sludge through the muck?  (not to mention the BS).

Even when measuring blood values, there is cause for concern.  In the calcium:phosphorus issue, for example, an undersupplemented cat or dog will not show signs - even in their blood values - for quite some time.  Their bodies compensate by leaching calcium out of their own bones to maintain proper levels in the bloodstream.  Given their bone stores of minerals, a deficiency must be awfully long-term to cause a problem unless that deficiency is extremely severe - and even then the symptoms may be overlooked.

<sigh> 

Overall, I prefer to err on the side of caution.  In the meantime, we rotate as much as possible, feed a variety of home made items as well, and perform regular bloodwork. 

For now I would be happy to see more accurate labeling requirements.  As in, unique batch labels rather than "min" and "max" labeling.  At least this would force each company to test each lot - and provide us some recourse if the results don't equal the advertising.

BTW, the Winn Foundation has just funded a study on raw fed kittens re: nutrition and immunity benefits.  It's certainly a step in the right direction.   

The study was just announced - not sure about the timeline, I would guess at least a year.

http://www.winnfelinehealth.org/Pages/WinnGrants2009p2.html