The food data tables
have quickly become one of the most popular parts of this website.
The tables list many American
and British cat foods
in order of their phosphorus, protein, sodium and fat content.
These data are calculated on the basis of
dry matter analysis. I
know many people are very confused about why the data in the tables differ so much from
the percentages shown on the cans or on manufacturers' websites.
I also know many people
think they can just rush out and buy the first food on the list that their
cat will eat but unfortunately it's not that simple.
Please read below to understand why
the food data tables are calculated in this way and how best to use them.
Please read this
page before contacting me to tell my data are incorrect - chances are you
have misunderstood how I calculate the data. Yes, I know the information on the
cans is not the same.
If you wish to go
straight to the links to the tables, click
here.
Unfortunately there
are a number of different ways of assessing food content, which can make
choosing a cat food a very confusing exercise. All these methods have their pros
and cons.
Most US manufacturers
provide their food data in the form of
Guaranteed Analysis
(GA). You may also see references to As Fed data.
Most UK manufacturers
provide their food data in the form of Typical Analysis.
This page explains
the differences between the different methods and why I use dry matter analysis.
Guaranteed
Analysis - Used in the USA
Virtually all US
cat food manufacturers provide their food data as Guaranteed Analysis (GA).
This is to comply with AAFCO (Association of American Feed
Control Officials) guidelines. AAFCO is responsible for overseeing pet
food production in the USA, and its guidelines cover the production, labelling,
and sale of pet foods.
Unfortunately,
guaranteed analysis is of only limited use when trying to compare foods for
CKD cats. This is because guaranteed analysis only provides maximum and minimum values,
and the only ones which are compulsory are protein and fat (minimums), and fibre and moisture (maximums). If phosphorus is
shown (and it is not compulsory), it is usually given as a minimum. This makes it very hard
to assess whether a food is suitable for a CKD cat, for whom you
need to know the exact amount or at the very least the maximum amount of
phosphorus in particular. The minimum is potentially very misleading. For example, I could
tell you "I have a minimum income of US$25,000" when in fact my
income was US$250,000. I wouldn't have lied; on the other hand I
wouldn't have given you meaningful information either.
Here's an
example of how this affects foods. Let's say we are looking at a food with the
following GA figures:
moisture: max 80%
phosphorus: min 0.20%
If we assume these values are correct, this gives us a
dry matter analysis figure (see below) of 1% for
phosphorus.
Now let's say the actual figures are:
moisture: 79.0%
phosphorus: 0.25%
This gives us a DMA figure of 1.19% for phosphorus, so very different from the
figures we came up with if we used GA figures.
Because of this,
and because so many manufacturers are unable to provide information on a Dry
Matter Analysis basis (in fact, a fair number don't even seem to realise there
is a difference), there are quite a few foods missing from the tables. We
are continuing to liaise with the manufacturers regarding the missing data.
Typical
Analysis - Used in Europe
Virtually all
European cat food manufacturers provide their food data as Typical Analysis.
This is to comply with
EU legislation. Regulation
183/2005/EC on Feed Hygiene covers the safety of all feed, including pet food,
in Europe.
The UK Food Standards Agency has more
information about the legal requirements for pet food. In the UK, over 90% of pet food manufacturers are also members of
the Pet Food
Manufacturers Association, and comply with its guidelines.
Unfortunately,
typical analysis is of only limited use when trying to compare foods for CKD cats. This is because,
although it is more reliable than Guaranteed Analysis,
it does not allow for the moisture content in the food.
What we really need is
dry matter analysis (DMA).
Dry Matter Analysis - Used on This Website
Cat foods vary in
how much moisture they contain, which makes it difficult to
compare them to each other. It is very hard, for example, to compare a tinned
cat food to a dry cat food because the former naturally contains much more
water; and this affects all the percentages of the different nutrients. Dry matter analysis is
a way of comparing foods by assuming all the moisture content has been removed: this makes
it easier to compare different products. Whenever this site mentions levels of
the various components of foods, it is talking about them on the basis of dry
matter analysis, which is not necessarily the same as what it says on the can.
Let's take an
example. Let's say:
you give your cat a
food with 80% moisture, a typical level for many tinned foods;
the food apparently
has phosphorus of 0.25%;
your cat eats 100g
of the food.
It therefore
appears that your cat is eating 0.25g of phosphorus (100g x 0.25%).
However, the food
is 80% water. So of the 100g your cat has just eaten, 80g (80%) of it was
simply water, and only 20% was actual food, or dry matter. So the amount of
phosphorus is actually higher - in percentage terms - than it first appeared,
i.e. your cat has eaten 0.25% divided by (100%-80%) or 1.25% phosphorus.
Another way of
looking at it is to say that your cat food initially had 1.25% phosphorus.
Then the manufacturers added 80% water. There is still the same total amount
of phosphorus in the food, but at first the percentage appears lower because
of the diluting effect of the water. So in order to understand exactly how
much phosphorus your cat is eating, you need to discount the water in the
food.
There are other
ways of calculating the values in cat foods. One which some manufacturers like
to use is Metabolisable Energy (ME). This can be useful, because it gives you
some idea of how calorie dense a food is. The main reason I use Dry Matter
Analysis is because that is the format which leading vets use when making
recommendations for target nutrient intake.
Calculating
Dry Matter Analysis Yourself
You shouldn't often
need to calculate dry
matter yourself because I've already done it for many foods. If you do
want to do it yourself, you need to know the amount of moisture in the food and the
amount of whatever you are measuring (often this will be phosphorus), and then
you need to crunch the numbers a little.
Let's assume you
have a food with a moisture content of 76% and a phosphorus content of 0.2% on
an As Fed basis. This is the formula:
The dry matter in a
food is always 100 - (% moisture in the food). So in this example, with 76% moisture,
100-76% leaves 24% dry matter.
You then have to divide the phosphorus content by the dry matter.
In this case, you would divide 0.2 phosphorus by 24% dry matter, which gives 0.833% phosphorus content of this food on a
Dry Matter Analysis basis.
Remember, using the data from cans of food in
the USA for this exercise is often unreliable because the data on the cans
tend to be maximums or minimums rather than actual data.
Please don't just
rush out and buy the first food at the top of the list! There are a number of
issues to consider when choosing the best food for your cat's particular
needs.
The tables
simply provide information on the amount of the various components of the
foods. This is only half the story. There is also the question of the quality of
different cat foods, particularly what constitutes a
high quality protein and which ingredients are the best. You can read more about these issues on the
Which Foods to Feed and
Nutritional Requirements pages. If you want to
check the actual ingredients in a food, either visit the manufacturer's own
website (there are links to lists of US and UK manufacturers and their website addresses
here) or
visit a site such as
Pet Food Direct which tells you the
ingredients of the foods it sells. If you'd like to discuss the various foods
and ask what has worked for other people, join
Tanya's CRF Support Group.
You also need to
consider the calories in a food.
I am often asked if I could add calorie details to the
food data tables. I do plan to do this, but in the meantime you can find the
calorie content of some US foods
here (canned)
and
here (dry). If the food you are interested in
is not included there, check the manufacturer's website. Generally speaking,
lower fat foods have fewer calories, as do gravy foods.
AAFCO Minimum
Levels
US commercial adult
foods certified as complete must meet the AAFCO guidelines
for adult maintenance foods. These are the minimum levels permitted by AAFCO
(fibre is the only component which has a maximum level):
Dietary Component
Minimum Level (% on a DMA Basis)
Phosphorus
0.50
Protein
26.00
Sodium
0.20
Fat
9.00
Phosphorus
If your cat's
phosphorus level in blood tests is too high, this will make your cat feel ill
and may make the CKD progress faster.
In order to reduce
these risks, your goal is to have your cat's serum level of phosphorus (i.e.
what your vet tests in bloodwork) no higher than 4, although many people do
not try to actively control their cat's phosphorus levels with phosphorus
binders until the level is closer to 6.
The easiest and
most effective way to control phosphorus levels is by feeding foods low in
phosphorus.
Ideally you want to
feed a food with a phosphorus level
under 0.5% according to Dr Scott Brown in
Management of feline chronic renal failure
(1998) Waltham Focus8 (3). No commercial adult food which meets
AAFCO guidelines will meet this requirement because the minimum phosphorus
level required by AAFCO is 0.5%.
If your cat won't
eat the prescription foods, you still need your cat to eat. Since the minimum
level of phosphorus in a non-prescription food is 0.5%, you are not going to
find a commercial food with phosphorus below 0.5% like most prescription
foods, but you may be able to find a food in the table which has a low
level of phosphorus which your cat will eat. The table lists foods in order of
phosphorus content so you can clearly see which foods might be worth
considering.
In order to keep
your cat eating, you may have to have a less ambitious goal, at least to start
with, of, say, feeding a food with less than 0.75% or less than 1%
phosphorus.
But your ultimate
goal should be to feed the lowest phosphorus food that your cat will eat.
Whichever food you
opt for, always introduce a new food gradually (mix it with the food you've
been using previously and gradually increase the percentage of the new food) so
as to reduce the risk of tummy upsets.
Protein
The need for lower
protein food for CKD cats is much debated, and may not be necessary for cats
in the early stages of CKD. See
Nutritional Requirements for more information.
However,
since BUN levels are influenced by diet, it does often help the cat feel
better if you restrict protein intake, particularly as the CKD progresses and
BUN rises.
Most prescription
foods have protein levels of between 25 and 30%, usually around 28%.
When choosing a
commercial food from the lists, therefore, I would not only look at the
phosphorus level but also consider the protein level. That is to say, if for
example I have two foods with the same phosphorus level to choose from and my
cat will eat both of them, and one food has 32% protein while the other has
50% protein, I would normally choose the lower protein food.
Ohio State University College of Veterinary Medicine states that protein
should never be reduced to less than 20% of calories (scroll down to the
slides labelled Conservative Medical Management of CKD: Protein
Restriction).
Sodium
Since CKD cats are
prone to high blood pressure, it is generally advisable to try to feed a food
low in sodium.
In fact, one study,
Effects of sodium chloride on selected parameters in
cats (2006) Kirk CA, Jewell DE, Lowry SR Veterinary
Therapeutics: Research in Applied Veterinary Medicine7(4)
pp333-346 found that there was actually no change in blood pressure in the
CKD cats in this study, but levels of BUN, creatinine and phosphorus were
higher in the cats eating a high sodium diet compared to those eating a low
sodium diet.
The sodium content of the prescription renal diets varies widely. The
minimum level permitted by AAFCO is 0.2%. It is unlikely that you need to go
much higher than this.
As with protein, I
would factor this into choosing a food. If for example I have two foods with
the same phosphorus level and a similar protein level to choose from and my
cat will eat both of them, and one food has 0.3% sodium while the other has 1%
sodium, I would normally choose the lower sodium food.
Fat
As with protein, cats need relatively high levels of fat compared to a human
or dog.
Fat does not result in a lot of waste products like protein, so processing
it is not a strain on the kidneys. In fact, in most CKD prescription foods,
the fat content is increased to compensate for the lower protein levels.
Therefore a diet relatively high in fat can help an older cat to maintain
his/her weight while placing less strain on the kidneys.
In other words, if you have a choice of two similar foods and you wish to
maintain or even increase your cat's weight, it is probably better to choose
the food with the higher fat content.
A small team from
Tanya's CRF Support Group
and the German CKD group, nierenkranke Katze,
has spent hours contacting the various manufacturers to obtain the correct
information, and I have then crunched the numbers where necessary. A huge
thank you to Amy, Anna, Anne, Cher, Elise, Elizabeth, Joy, June, Karen, Kim, Larry,
Lee, Leslie, Marion, Melinda and Nancy,
who I'm sure would never have signed up if they had known what tedious hard
graft this would be, but whose efforts are truly making a difference to CKD
cats' lives.
These analyses have
been compiled in good faith from the information provided to the team by the
manufacturers. Where possible, we have obtained the data in writing in order
to avoid any misunderstandings. The data may not necessarily match the
information on the cans, which show maximum values for moisture and phosphorus
rather than actual values.
Unfortunately food
formulations can change without warning, and therefore I cannot guarantee that
the data are still
accurate; no responsibility can be accepted. Several of the manufacturers have
asked me to emphasise that their non-prescription
foods are not intended for CKD cats.
Having asked
repeatedly, in November 2011 we finally accepted that we are never going to
obtain any data from Almo Nature, they simply do not appear to understand the
concept of dry matter analysis and tell us that their foods are basically just
the same as their ingredients, so if we look up, say, chicken, that should be
sufficient. The mind boggles. Personally I would not feed something made by a
manufacturer incapable of providing basic information about its own products.
For those juggling
more than one health condition, the table also
includes data for other
prescription foods. US
baby foods are also included
in the US canned food table since they can be very helpful in getting a CKD cat to eat. Although I don't recommend feeding
raw foods to CKD cats, since I know some people may already be feeding
them, data for these foods are included. Treats will be
added in due course.
IMPORTANT:
foods marked * in the table are NOT complete foods and should NOT be fed exclusively.
