Fish flavored canned catfoods and magnesium

Prompted by a previous thread on feeding fish to cats I have determined to
once and for all understand the magnesium levels in canned cat foods and how
it relates to FLUTD, especially with regards to male cats.

I understand that human grade fish is far too high in magnesium to consider
feeding, so ask that we confine ourselves to discussing only canned fish
flavored catfoods. I am also assuming that we all know that getting our cats to drink enough water is crucial.

There is a common maxim saying "fish no more than once per week" as
excessive magnesium plays a part in the formation of the most common
uroliths, struvite.
But frighteningly- this site (which I really love) says "The incidence of calcium oxalate urolithiasis in cats has increased while struvite urolithiasis has decreased during the past several years. It is theorized that the widespread feeding of acidifying diets that contain low levels of magnesium may be a contributing factor to this trend."

So too little magnesium is as detrimental as too much- got it.

Can I feed California Natural "Deep Water Fish" flavor with a magnesium
content of 0.30% more than once a week? Felidae Chicken/Lamb/Turkey/Fish at 0.25% ? All the Merrick brand canned foods are 0.25% magnesium- Cowboy Cookout (beef), Ocean Breeze, Pot Pie- all of them. Even the Fancy Feast fish flavors now advertise "low magnesium", which according to
this article means "With respect to dietary magnesium levels, the FDA's 'cut-off' criteria to support a "low magnesium" claim are: less than 0.12% on a dry matter basis".

I am trying to develop a rotation of canned food flavors that 1)all three of
my cats will eat, and 2) provide optimum nutrition without fostering high
urine pH. I have purchased 29 different brands and flavors of canned cat
foods in the past two weeks, and am charting which cats will eat which
flavors- I had to create a spreadsheet to keep track of it all.

So..... my question is:
Can I use any of my chosen fish flavored formulations daily, or must I
limit the fish flavored varieties to only once per week even though they contain lowered levels of magnesium?
Isn't 0.25% magnesium the same regardless of whether it is fish or chicken, and I can stop worrying about the fish once per week thing?


If you have made it this far, thank you. If you can offer any comments or
recommed reading I truly appreciate the time it takes you to do so.

And yes- I always overthing everything

As long as you're feeding a cat food that is formulated to be low in magnesium you can stop worrying about it. That level of low magnesium 0.25% is the same whether it's chicken or fish as long as the label reads it. You might want to be concerned about mercury levels. Some pet food companies will test their fish to make sure there are no detectable levels of mercury before putting the food on the market and they get their supply from oceans that have far less mercury than other areas. But you may want to look into this and ask questions before deciding on a food. However I have not heard of nor seen any news reports about cats getting ill from mercury poisoning so there must be some pretty good quality control. But for the sake of good nutrition and a varied diet, I would definitely vary the meats that are in cat food, chicken, turkey, duck, beef, lamb and so on.

I think in part it depends on whether or not you know if your cat(s) are already showing signs of crystal formation, and if so, which type.

This article http://www.peteducation.com/article....articleid=2729 is well written, and you'll notice that when discussing magnesium levels and calcium oxalate stones, it says that magnesium should not be reduced (nor supplemented). A moderate level of magnesium is best.

My feeling is 1) there are human grade fish cat foods out there, so I do not agree with your point that human grade would contain too much magnesium, 2) magnesium levels are magnesium levels - be they from a fish based, or poultry etc. based canned food.

Moderation, variation of proteins/foods fed, perhaps doing urine ph testing to see what your cat is doing, considering frequency of feeding (again, see article I gave the link to and it's discussion of meal frequency and the acidity or alkalinity of urine), increasing cats water intake, all are factors to consider.

My 2 cents,

I of course agree with Pat ... but my vet said no fish or no more than one can a week with fish for my Kandie ... And her utis stay away as long as I keep her on that diet...

Sure there are human grade fish cat foods.

I think the poster is talking about canned tuna for human consumption, which is not intended for cats to eat.

Originally Posted by moggiegirl

Sure there are human grade fish cat foods.

I think the poster is talking about canned tuna for human consumption, which is not intended for cats to eat.

Click to expand...

Well I made the point because they said "human grade fish". There is human grade fish canned cat food...that is my point.

Originally Posted by moggiegirl

I think the poster is talking about canned tuna for human consumption, which is not intended for cats to eat.

Click to expand...

Yes- I guess I chose the wrong words.
When I said "human grade" fish I meant fish bought in a human grocery store to prepare for human comsumption- whole fish- salmon, orange roughy, tilapia, etc.
Not a formulated catfood.

The cats in question get a broad range of foods,including a prepared raw diet and California Natural dry as a snack. They are all three nine month old neutered males with no health issues, and I hope to keep them that way. I do intend to keep offering as wide a variety as they will eat but they are showing a distinct preferance for fish flavored wet foods, and having heard the "fish once a week" thing I was concerned.

Originally Posted by Cearbhaill

Yes- I guess I chose the wrong words.
When I said "human grade" fish I meant fish bought in a human grocery store to prepare for human comsumption- whole fish- salmon, orange roughy, tilapia, etc.
Not a formulated catfood.

The cats in question get a broad range of foods,including a prepared raw diet and California Natural dry as a snack. They are all three nine month old neutered males with no health issues, and I hope to keep them that way. I do intend to keep offering as wide a variety as they will eat but they are showing a distinct preferance for fish flavored wet foods, and having heard the "fish once a week" thing I was concerned.

Click to expand...

Fish is fine barring trouble ./... my vet feeds her cats fish a number of days a week

You know why cats like fish so much? Just because it stinks. Cats rely very heavily on their sense of smell to be attracted to food. While cats definitely have preferences for certain smells and textures their sense of taste is actually quite poor compared to a human.

I think the once a week rule applies to foods that are made up exclusively or predominantly of fish. Like you can get canned tuna for feline consumption in which they add vitamins and minerals to the food to make it nutritionally complete and balanced according to AAFCO standards. But it's still not good to feed this food exclusively. It's just tuna after all. Or it may also apply to feeding fresh cooked fish as a treat.

I just love those thin bonito flakes, also called Kitty Kaviar. That stuff is like tuna flavored air. You can be generous with it and don't have to worry about it.

Pat, I am going to ask some questions regarding this quote, can you elighten me?

Originally Posted by Pat & Alix

I think in part it depends on whether or not you know if your cat(s) are already showing signs of crystal formation, and if so, which type.

This article http://www.peteducation.com/article....articleid=2729 is well written, and you'll notice that when discussing magnesium levels and calcium oxalate stones, it says that magnesium should not be reduced (nor supplemented). A moderate level of magnesium is best.

My feeling is 1) there are human grade fish cat foods out there, so I do not agree with your point that human grade would contain too much magnesium, 2) magnesium levels are magnesium levels - be they from a fish based, or poultry etc. based canned food.

Moderation, variation of proteins/foods fed, perhaps doing urine ph testing to see what your cat is doing, considering frequency of feeding (again, see article I gave the link to and it's discussion of meal frequency and the acidity or alkalinity of urine), increasing cats water intake, all are factors to consider.

My 2 cents,

Click to expand...

When looking at magnesium levels on cat food labels, what exactly is moderate? My Ophelia is on SD s/d because of crystals in her urine. I'm not sure which kind, but a member here said struvite because she is on s/d. I'll be sure to find out which type on Wednesday when I take a urine sample in.

The urine pH testing, how exactly is that done? By a vet or at home?

Sorry I hijacked your thread Cearbhaill.

.085% is generally considered low in a dry foods

.025% in a wet food

Originally Posted by white cat lover

Pat, I am going to ask some questions regarding this quote, can you elighten me?



When looking at magnesium levels on cat food labels, what exactly is moderate? My Ophelia is on SD s/d because of crystals in her urine. I'm not sure which kind, but a member here said struvite because she is on s/d. I'll be sure to find out which type on Wednesday when I take a urine sample in.

The urine pH testing, how exactly is that done? By a vet or at home?

Sorry I hijacked your thread Cearbhaill.

Click to expand...

Bother, I just lost my entire reply. Per the article I linked to, they quoted the fda as listing .12% by dry matter analysis as low magensium. I'd honestly ask my vet what they would consider moderate/mid range level to be.

You can buy urinary test strips that allow you to test the urine for ph (and protein, glucose and more depending on what you buy).

Since s/d is used to help treat struvite crystals (dietary approach is not effective in disolving calcium oxalate crystals), it's probably a safe bet that is what your vet feels you are dealing with.

Best wishes with the upcoming visit, and please keep posting on how things are going.