Starting with the food label: not as helpful as you’d think
Many people find analyzing cat food confusing – and often the first time they really think about what’s in their cat’s food is after diagnosis of some disease like kidney disease or diabetes, which is stressful enough to deal with on top of having to figure out how to compare percentages!
How much protein is in my cat’s food? How much phosphorus? Carbohydrates? Most people start with the food label, which unfortunately is not as helpful as you might think and may be misleading. For foods made for sale in the US (and also sold in other countries), the label will list a guaranteed analysis – an FDA requirement mostly, that gives you a few percentages like protein…but rarely (if your cat has kidney disease) the phosphorus content and never the carb content. For some of this stuff, you need to get more information from the manufacturer. (Sometimes on their website.)
But even with the things that are on the label like the protein (and sometimes phosphorus): the percentages in a guaranteed analysis first of all are minimums and maximums. If I want to know how much protein is in a food, telling me it’s “at least” 8% protein doesn’t mean it isn’t 9% or more! What is more helpful (read within) is a typical analysis – an average content in the food. That’s something else you to get from the manufacturer or find on their website.
The second issue with the percentages in a guaranteed analysis or on any food label is that they are always “as fed” – which means “as you feed it” – including the water. Water doesn’t contain protein (or phosphorus, etc.) but does make up about 75% of most wet food…yet that 8% includes the water. It dilutes it. And every food has a different moisture (water) content, so no two foods will be diluted in the same way. You might look at two foods, one with 8% protein “as fed” and the other 9% and think, “The 9% must be higher!” but it may not be. Or you compare a bag of dry food with a protein of 30% “as fed” to a can that’s 9% and think, “Wow, the dry food is a lot higher!’ But…probably not. There’s almost no water in the dry food to dilute it – so it just looks higher.
This all confuses the heck out of most people when they start looking at food labels!
Don’t worry – we’ll get into all of this below. Keep reading!
The main thing to remember, though, is: if you are worried about limiting your cat’s intake of something like phosphorus (for kidney disease), you want find a food from which your cat will consume the least phosphorus which may not be the same as “food that seems lowest in phosphorus.” That may sound both obvious and confusing – but it’s not quite the same thing. Here’s the difference: you might have two cans of food that have exactly the same amount of phosphorus each can, but…because foods differ in their calorie content, your cat may need to eat more of one than the other. We’ll learn below how to compare foods in a way that takes that into account, so you can just compare two foods and say “my cat will consume less phosphorus from this one.”
What do I really need to know to analyze/compare pet foods?
If you are new to analyzing foods and really confused about terminology, you might skip this section for now until you learn more. All the terms will explained further down. This section is for readers who are already at least semi-familiar with some of this stuff. This is how I look at foods myself.
In an ideal world, I’d want a nutrient profile that uses a calorie basis (ME Profile for protein, fat carbs…and mg/100kcal for minerals) …or a dry matter basis. Either one works, though I prefer a calorie basis. “As fed” is not sufficient without doing some math.
And I want a “typical analysis” (averages) – not “guaranteed analysis” (minimums/maximums).
If all I get are “as fed” percentages, then I’ve got some math to do. If I have the moisture, I can easily calculate the dry matter basis using this DMB calculator. If I the Metabolizable Energy (ME) in kcals/kg (calories per kg) I can calculate the calorie basis (mg/100kcal) for the minerals like phosphorus e.g. using this mg/100kcal calculator.
I can calculate the ME Profile if I have typical analysis percentages for protein, fat, and carbs (either “as fed” or dry matter basis – either will work) – using this ME calculator. If I don’t have carbs but have fiber, ash, and moisture percentages, I can estimate carbs (and calculate the ME Profile) using the same ME calculator.
What if all I have is the guaranteed analysis – minimums and maximums only? Then I really can’t get a good carb estimate – just a rough guess (so I’ll be looking at the food ingredients for plant ingredients to try to guess if the food is very high in carbs or not). I can get a rough idea about protein and fat. I can guestimate that for foods sold in the US, minerals like phosphorus are no more than 50% higher maximum than the minimum…so about 25% higher than minimum to estimate a typical/average percentage. But really…I want a typical analysis! Sometimes you get a guaranteed analysis for the protein, fat, and moisture but a typical analysis for the minerals. Again, every company has a different way of doing this!
What is Dry Matter Basis?
As we said above, food labels show percentages on an “as fed” basis which doesn’t help us compare cat foods, since each food has a different moisture content that dilutes the nutrients. Your cat may consume more protein from one cat food that is “8% protein” than another that is also “8% protein” if they have different moisture contents. So how do you know which one provides more protein?
There are two much better ways to compare foods than “as fed” percentages. The most common of the two is called Dry Matter Basis. (The other way is a “calorie basis” – explained later.)
Dry matter is the part of the food that would remain if you could remove all of the moisture from it – the dry matter includes the meat, any plant ingredients, vitamin and mineral supplements, etc. The dry matter is the part we care about – where not just the calories come from but also minerals like phosphorus; they don’t come from the water. (Water and moisture are the same thing.)
If a food is 80% moisture, it is 20% dry matter. (The total adds up to 100%.) When you are looking at things like protein, phosphorus, etc. it is helpful to compare the percentage in the dry matter with the water factored out. (What percentage of that 20% is protein? or phosphorus? etc.) Then you can compare foods of all different moisture amounts the same way – even compare a wet food to a dry food. (Even dry food has some moisture in it – not much, typically 8% to 10%.)
Calculating the dry matter basis of any food is a simple math problem, if you have the moisture content also. There is no need to do the math yourself if you use a dry matter basis calculator like this one. All you have to do is plug in the two percentages – e.g. if protein is 8% and moisture is 80%, plug those into the calculator and you get 40% dry matter basis. If the protein on another food is 8% and moisture is 85%, you get 53.33% DMB, so your cat will consume more protein from that one than from the one with 80% moisture. 53.3% is higher than 40%, obviously.
(If you really need to know the math to calculate % DMB, it is explained on the calculator page for Dry Matter Basis.)
If you look at a food list, the dry matter basis may already be calculated for you, so you don’t have to calculate anything in that case. Just make sure it says “dry matter basis” on the list.
Examples: Dry Matter Basis vs. As Fed
Just to persuade you that comparing foods on an “as fed” basis is not useful, here are some examples using dry matter basis instead.
Example 1:
Food A and Food B both have a protein of 8% “as fed.” But Food A has a moisture of 78% while Food B has a moisture of 82%. Which one is “higher” in protein?
Let’s say both foods are the same can size – 100 grams (to make the math easier). Each can contains 8 grams of protein (0.08 x 100 = 8 grams). So, aren’t they both the same? Yes, it’s true each can contains the same amount of protein (8 grams)…but your cat has to eat more of Food B, because there is less dry matter in it – fewer nutrients. Maybe your cat needs to eat one and a quarter cans every day of Food B but only one can of Food A – so that’s 10 grams of protein every day if you feed Food B instead of just 8 grams if you feed Food A.
This is obvious if you calculate the dry matter basis: for Food A, with 78% moisture, it is 36.36% DMB, while Food B with 82% moisture, has a protein of 44.44% DMB. You know Food A is lower – because 36.36% is lower than 44.44%.
Example 2:
Food C has a phosphorus of 0.12% “as fed” but 85% moisture. Food D has a phosphorus of 0.16% “as fed” but 78% moisture. Which one is higher in phosphorus?
Using the % DMB calculator, we find that Food C has a phosphorus of 0.8% DMB, while Food D has a phosphorus of only 0.73% DMB. So Food C is higher in phosphorus…even though “as fed” it looks lower. (Your cat has to eat more of Food C, since it has more moisture and less dry matter in it than Food D.)
Example 3:
A wet food is 78% moisture with 10% protein “as fed.” A dry food is 10% moisture with 30% protein “as fed.” Which one is higher in protein?
The wet food is 45.45% protein on a DMB according to our calculator. The dry food is 33.33% DMB. So..the wet food is much higher in protein.
Analyzing foods using a calorie basis
Wait a moment – you just convinced me that dry matter basis is the best way to analyze cat foods, because “as fed” is not good enough. Now you’re telling me there’s another way???
If you stick to dry matter basis, that’s fine with me – much more useful than “as fed!” But…DMB has a limitation. It is based on the weight of the food – the amount you feed. It removes water from the comparison of two foods. But it doesn’t account for differences in calories between two foods you are comparing. Some foods are more calorie-dense than others, meaning that your cat has to eat less of a calorie-dense food than one that is less dense, even if you feed the same amount (ounces, grams, cans, whatever). If you have to feed one can of a calorie-dense food, maybe you’ll need to feed one and a quarter cans of one that is less calorie-dense. And that affects how much or little of something your cat consumes.
The thing that messes up dry matter basis is differences in fat content. Fat is much more calorie-dense than protein or carbs, about 2x more calorie-dense than either. If you have two foods that are both say 0.7% DMB phosphorus, but one is much higher in fat than the other, your cat needs to eat much less of the fatty food and so will consume less phosphorus. If the two foods are roughly the same fat content, then % DMB is still a good way to compare them.
Nutrients and Minerals as grams per 1000 calories (or mg/100kcal – mg per 100 calories)
Instead of a percentage of the dry matter, a calorie basis uses a ratio of weight to calories – grams per 1000 calories (or for minerals, when the amounts are small, mg per 100 calories). A typical renal diet for example is roughly about 0.4% to 0.5% phosphorus on a dry matter basis…or roughly 100 mg/100kcal (100 mg for every 100 calories fed).
The key idea here is: your cat needs to consume about the same calories every day, whether it’s from a high fat, calorie-dense food or a low fat food. The weight or amount you feed isn’t as important – it’s the calories (given as kcals on the food label). If two foods both have a phosphorus of 0.7% DMB but one is 130 mg/100kcal while the other is 160 mg/100kcal, your cat will consume less phosphorus from the one that’s only 130. So why not feed that one, if your cat will eat both? If you relied solely on % DMB, you wouldn’t be able to tell the difference.
Metabolizable Energy (ME) Profile: Percentage of calories from protein, fat, and carbs
As with minerals like phosphorus, you can look at protein, fat, and carbs by calories. You will sometimes see them expressed as g/1000kcal (grams per 1000 calories). Minerals often use mg/100kcal instead just because the amounts are much smaller…but they are the same thing with different units.
Another method to look at protein, fat, and carbs on a calorie basis is called Metabolizable Energy (ME) Profile. Since all of the calories in cat food come from protein, fat, and carbs – all adding up to 100% – you can compare foods based on the percentage of calories. This is an elegant way compare foods and my favorite method.
E.g. a food that is 30% of calories from protein is lower (when your cat consumes it) than one that is 40% of calories from protein, as you would expect. So if your goal is to limit protein intake, aim for a food lower in protein as a percentage of calories.
One confusing thing to some about % of calories is that it is not the same thing as % dry matter basis! A food that is 30% of calories from protein is not the same as a food being 30% dry matter basis. (30% of calories from protein is probably 35% to 45% DMB – you can’t convert directly from one to the other).
So why would I use ME Profile – % of calories – instead of % DMB Because different fat content in foods throws off the % DMB comparison. If two foods are both about 30% of calories from protein but one is 35% DMB while the other 45% DMB and you are trying to limit the protein, which one would you feed? If you feed the same number of daily calories from either food, then your cat consumes the same amount of protein from both.
Or if you have two foods that are both about 38% DMB protein but one is 26% of calories while the other is 33% of calories…you might think your cat consumes the same protein from either…but he doesn’t, if you feed the same number of daily calories.
You wouldn’t know there was a difference if you looked at just the % DMB.
Some manufacturers provide their nutritional data only on calorie basis, not on a dry matter basis at all. (Every companies likes to do things differently!) So you will probably want to get an idea of what a calorie basis means if you don’t find the DMB listed on a manufacturer’s website.
If two foods have about the same fat content, then % DMB is still an accurate way to compare something like protein (or carbs). It’s the different fat content between foods that throws off the comparison. If you use a calorie basis like ME Profile, the difference is obvious.
Calculating the ME Profile is much harder than calculating % DMB for protein, cat, or carbs – you need all three of those to calculate the ME Profile, and you can’t find carbs on a food label. You can use this calculator to calculate ME Profile if you have the protein, fat, and carbs. It’s easy to calculate % DMB for protein if you have only the food label, because you also have the moisture there.
You might stick to % DMB if you find that less confusing than ME Profile or a calorie basis. But if the calorie basis has already been calculated for you (e.g. on a food list or on the manufacturer’s website), it’s a better way to compare foods, in my opinion, since it corresponds better to how much of something your cat actually eats.
Guaranteed Analysis vs. Typical Analysis
Guaranteed Analysis is what you find on a food label. In the US, it’s required to be on the food label. Sometimes it’s the only information you have for food.
Unfortunately, guaranteed analysis – minimums and maximums – is not that accurate or useful. And it’s usually missing things like phosphorus anyway. It gives you a rough idea of what’s in the food – that’s it. The percentages are always “as fed” meaning they are diluted by the water in the food, and since every cat food has a different moisture content, it’s impossible to compare “as fed” percentages easily.
A Typical Analysis, on the other hand, is much more precise and useful. Instead of minimums and maximums, the percentages are “average” or typical percentages, more representative of what’s actually in the food. A food may be 9% (minimum) protein, but is probably higher, maybe much higher, in a typical lot of food.
Typical analysis is never on a food label. You have to get it from the food manufacturer. Sometimes it is on their website. It’s worth getting if you can get it!!! Often you must contact them to ask for it. Many companies will provide typical analysis if you ask – sometimes they called it a “nutrient profile.” Sometimes a nutrient profile shows the guaranteed analysis for protein, fat, and moisture (indicated by the words “min” and “max”) but typical analysis for the minerals like phosphorus. If in doubt, ask them which it is. (Hint: guaranteed analysis numbers are often rounded to round numbers – so if the protein is 9%, fat is 5%, moisture is 78%…it’s more likely guaranteed, whereas if they are not rounded – like 9.2%, 5.13%, moisture 77.2%…then it’s more likely to be a typical analysis.)
While guaranteed analysis always uses “as fed” percentages, a typical analysis can use any basis – “as fed,” dry matter basis, or sometimes a calorie basis. Unfortunately, every food maker likes to use their own method of showing nutrients, so comparing foods between manufacturers may not be easy.
Every food maker has a nutrient profile with typical analysis for their foods – they had to create one for any food that is claiming to meet an AAFCO nutrient profile…but some choose not to share it with consumers or not all of it. To see an example of what an AAFCO nutrient profile looks like, check out the Wellness US website – this company provides a full page nutrient profile that looks like what they submitted to AAFCO, with more details about the food than I’ve ever seen from any other food company. (Maybe more than you want to know…and unfortunately, they don’t provide concise charts summarizing all of their foods in one place, like say Weruva does.)
So why can’t you compare the guaranteed analysis (minimums/maximums) from one food to the typical analysis (averages) of another food? Because you need to compare things on the same basis! It’s like trying to compare the temperature in Phoenix to the temperature in Tuscon. If we know that the temperature in Phoenix was 70 degrees at 5am but the average daily temperature in Tucson was 85 degrees…how can you compare them? You need the information on the same basis: either both minimums or both averages to compare them. You can’t meaningfully compare one type to the other.
It’s important to remember that meat is not a uniform ingredient! If you buy meat at the grocery store, the cuts are a little different each time, right? Sometimes it’s a little more lean or fatty than other times. Same with the meat used in cat food. And that means the protein, fat, phosphorus, etc. will never be exactly the same between different lots of food. So a “typical analysis” is an average. If the protein was 9.74% “as fed” in the typical analysis, sometimes it will be 9.5%. Sometimes it will be 9.9%.
And this is why some manufacturers don’t even bother providing a typical analysis to consumers. All they can guarantee is a minimum – why should they tell you anything else? But…most people prefer a typical analysis, and many manufacturers provide one.
Here are a few random examples of a few real cat foods (which shall remain nameless but are called Food A, Food B, and Food C) comparing their guaranteed analysis to their typical analysis, since these companies provide both. See how different they are? They are not always this far off but certainly could be.
| Food | Guaranteed Analysis | Typical Analysis |
| Food A | Phosphorus 0.15% (minimum) | 0.19% |
| Food B | Protein 8% (minimum) | 9.47% |
| Food C | Moisture 85% (maximum) Protein 7% (minimum) Fat 3% (minimum) |
Moisture 76.3% Protein 10.5% Fat 9.54% |
Check out Food C: the fat is three times higher in the typical analysis than the guaranteed analysis!
Estimating Typical/Average when you have only Guaranteed Analysis / Minimum Percentages
It’s always better to get a typical analysis for any food you are looking at, but what if you don’t have it? You can’t directly compare two foods if you have a typical/average percentage for one food but only the minimum for another.
For minerals (e.g. phosphorus, calcium, sodium), I’ve been told by several US pet food manufacturers that their maximum mineral content will never be more than 50% above their minimum. Using this rule, we can at least guess at an average mineral content if all we have is the minimum percentage. If the maximum would be no more than 50% above the minimum, then we can guess that 25% higher would be an average.
For example, if the phosphorus is 1.0% (minimum), we can guess it would be no more than 1.5% (maximum) (50% higher than the minimum – 1 x 1.5). So an average (guess) would be 1.25 x 1% = 1.25%
“as fed.” Again, this is a guess. It’s always better to get a typical analysis directly from the manufacturer instead.
As a further example…if you want to calculate the dry matter basis too…let’s say a bag of kibble shows a phosphorus content of 0.7% (minimum). To guess at an average, multiply by 1.25 (25% higher), which gives you 0.875% (average/typical) “as fed.” If you want to convert that to dry matter basis (discussed more below), if the food is say 8% moisture, then the dry matter would be 92%, and dry matter basis of 0.875% would be 100 x (0.875 /92) = 0.9511 (or round it to 0.95%). So…if you thought 0.7% phosphorus wasn’t that high, it’s quite a bit higher at 0.95% Dry Matter Basis (typical) compared to a renal food that is say 0.5% Dry Matter Basis.
Analyzing and Comparing Foods: Examples
Example 1: comparing two cans of food, one with “as fed” and the other with % DMB
Let’s say you look a can of cat food. You will probably find a Guaranteed Analysis on the label – percentages of minimums and maximums. The phosphorus is usually not listed there – but sometimes it is. Let’s say the can says Phosphorus 0.25% (min). I want to compare it to a can of renal food that is 0.45% Dry Matter Basis on the company’s website. So isn’t 0.25% less – lower?
No, it’s not – this first food is actually very high in phosphorus. Let’s go over it.
First remember that 0.25% is an “as fed” percentage – anything on a food label is (guaranteed analysis is always “as fed.”). We need to factor out the water if we want to compare it to other foods.
Second…it’s minimum. We use averages (normally part of a typical analysis) to compare things, not minimums and maximums. If the renal food is 0.45% DMB typical/average, we can’t compare it directly to something that’s a minimum. We need the average! (Remember above when we said we can’t compare the temperature at 5am in Phoenix with the average temperature all day in Tucson? ) Ideally the company would have a typical analysis…but this company doesn’t. If you call them, they’ll just read you that 0.25% (minimum) that you see on the label. That’s it. You have to guess at the average.
I follow the “25% above minimum” guideline (for minerals, for foods sold in the US) to guess at an average – not ideal but unless the company has a typical analysis. We can find out what’s 25% higher than 0.25% by multiplying it by 1.25…and that gives us 0.312% (average).
But…that’s still “as fed!” We need to factor out the water and calculate the dry matter basis to compare it to the renal food. You can use this Dry Matter Basis calculator.
Checking the label, I see it’s 78% moisture. My handy Dry Matter Basis calculator tells me that 0.312% “as fed” with 78% moisture is 1.42% DMB. (Spoiler alert: that’s pretty high – 3X higher than a renal food that’s 0.45% DMB.)
What about a calorie basis? I can figure the mg/100kcal for this food if I have the Metabolizable Energy (ME) – and I see it on the label, as 1,220 kcal/kg. I plug that along with 0.312% “as fed” (typical/average) into my mg/100kcal calculator (or divide 0.312% by 1220 and multiple the result by one million) and you get 256mg/100kcal. That’s still high but looks better than the % DMB (a renal food is about 100mg/100kcal, so 256 is about 2.5X higher).
Example 2: Random can food, comparing sources of data
Here’s another canned food: phosphorus on the label’s Guaranteed Analysis says 0.15% (minimum). Moisture is 80%. ME is 1,042 kcal/kg.
I wish I had more than the Guaranteed Analysis. But if that’s all I have at the moment…using the same techniques above, I can guess at the average phosphorus form the minimum (0.187% “as fed”) and we get 0.94% DMB…and 179 mg/100kcal.
But..wait! I contacted the company, and it turns out they have a typical analysis! They tell me these are the typical percentages, so I don’t have to guess:
Phosphorus 0.19% (as fed), moisture 79.05%. (So our guess of 0.187% was pretty close, right? That rounds up to 0.19%.) But the typical moisture is a little lower. With 79.05% and 0.19% “as fed” we get 0.91% DMB. Using that same ME of 1,042 kcal/kg, we get the mg/100kcal as 182mg/100kcal. These are basically the same as our guesses! So our “25% higher” guess was pretty good in this case. (This one is fairly low in phosphorus though still not nearly as low as a renal diet which is about 100mg/100kcal…but still far lower than something like Fancy Feast.
Example 3: compare the protein in two different canned foods
I have two cans of food from the same manufacturer. Here is the Guaranteed Analysis for each – I want to know the Typical Analysis if I can get it…but let’s start with the guaranteed and see how useful it is to compare foods based on that. (These are real foods and their actual percentages from the manufacturer, in case you are wondering.)
| Can W1 | Can W2 |
| Protein (min) 8.0% Fat (min) 1.2% Moisture (max) 87.5% ME 683 kcal/kg |
Protein (min) 10.0% Fat (min) 5.0% Moisture (max) 82.0% ME 1225 kcal/kg |
This is just the guaranteed analysis that you see on the cans. I can tell only limited information from it – but I can observe a few things:
- Can W1 is a much lower calorie food than Can W2. W1 has a far lower Metabolizable Energy – 683 vs 1225, almost half the calories! (ME is in calories per kilogram of food). At least, it is lower in calories in terms of what you pay for.
- Can W2 appears to be a much higher fat food – I can tell that by comparing the fat to the protein. In W1, the protein is almost 8X higher than the fat; in W2, it’s only 2X higher. Still, without a typical analysis, this is only a rough guess.
- Based on the crude numbers in the guaranteed analysis, the protein of W1 is 64% DMB while W2 has a protein of 55.56% DMB, so a little lower. But this is a crude estimate based on the guaranteed analysis – those are just minimums.
- It’s impossible to calculate the ME Profile based on just this information. (If say you wanted to compare protein that way – which I would prefer myself.)
But wait! This company happens to provide a typical analysis for both of these foods as well – so we can compare them much more accurately. Here is the typical analysis, and it includes carbs:
| Can W1 | Can W2 |
| Protein: 9.47% Fat: 1.9% Carbs: 3.68% Moisture: 84.5% ME: 683 kcal/kg |
Protein: 14.2% Fat: 10.1% Carbs: 0.25% Moisture: 73.7% ME: 1225 kcal/kg |
W1 is not far off from its guaranteed analysis, right? The protein comes out to be 61.1% DMB, a little less than the 64% guessed via guaranteed analysis.
But W2 is way off from the guaranteed analysis! The moisture is far less (73.7% instead of 82%). The protein in this one comes out to be 54% DMB.
From that we can see that W2 is indeed quite a bit lower in protein than W1, based on the % DMB.
But…these foods have a very different calorie density. W2 is pretty high in fat, much higher than W1. This will throw off our comparison if we stick to % DMB. Let’s calculate the ME Profile (% of calories from protein, fat, and carbs) for each – we can since we have a carbs number from the typical analysis. Here’s what you get:
| W1 ME Profile vs. DMB | W2 ME Profile vs. DMB |
| Protein: 61.1% DMB ME Profile (calorie distribution) Protein: 54% Fat: 26% Carbs: 21% |
Protein: 54% DMB ME Profile (calorie distribution) Protein: 37% Fat: 63% Carbs: 1% |
Wow, look at that! W2 is much lower in protein than W1 – 37% of calories vs. 54% in W1. That’s because W2 is really high in fat and W1 is low in fat – and fat is really packed with calories (and generally, good for cats; pancreatitis risk for cats is not substantiated by research FYI). We knew from comparing the % DMB that the protein was a little lower in W2, but really, your cat is going to consume a lot less protein from W2 than W1. And your cat will need to eat fewer cans of W2, since it is so much more calorie-dense.
(Plus, W1 is really high in carbs at 21% of calories. Not a good food for a diabetic cat! But W2 is great, only 1% of calories from carbs.)
But if you looked at the food labels and didn’t know any better…you’d think W1 (Protein 8% minimum) must be lower than W2 (Protein 10% minimum), but that’s quite the opposite of the fact. That’s why it’s important to look at these detailed analyses! Don’t go by the food labels!!! Or…if you don’t want to calculate all of this stuff, find a food list that already has all the math done for you, and compare the percentages there!
More examples
Example: which food is higher in protein?
Food A is 9% protein “as fed” with 82% moisture. and Food B is 10% protein “as fed” with 78% moisture – which is higher?
On a dry matter basis (use this % DMB calculator), Food A is 50% DMB. Food B is 45.45% DMB. If I have no other information, I will assume Food A is higher in protein. But…if the two foods have a very different fat content, maybe not. if I can calculate the ME Profile (use this ME Profile calculator), I can better compare them. To calculate the ME Profile, I need more information – namely, fat and carbs percentages, and I can’t get carbs from a food label. I need to get it from a manufacturer’s nutrient profile (a typical analysis, not a guaranteed analysis) to be the most accurate.
Let’s say Food A is 9% protein, 5% fat and 5.2% carbs…and Food B is 10% protein, 8% fat, and 1.4% carbs (“as fed” – but you can use % DMB too to calculate the ME profile). (Those are real percentages from real foods by the way.) Using the ME calculator above, for Food A I get an ME Profile (calorie distribution, total = 100%) of 34% protein, 46% fat, and 20% carbs. For Food B, I get Protein 33% protein, 63% fat, and 5%.
So…Food A is still higher in protein, on a calorie basis, but not much, right? Only 1% of calories higher in protein than Food B. To be honest, I would probably assume they are about the same…but because Food B much lower in carbs (since I don’t like high carb diets for cats), I’d want to food Food B anyway, if my cat would eat it…and since it’s much higher in fat (63% of calories from fat instead of only 46%), Food B is going to be much more calorie-dense. If I have picky cat who is thin and won’t each much, I have a better chance of getting her to eat more calories from Food B, assuming she likes it. She’ll have to eat less of Food B to get the same calories.
By the way – if you already know the ME profile (if it’s already given on the manufacturer’s website)…just start with that. If you already have the 34% of calories and 33% of calories from the two foods, just compare those: 34% is higher but barely. Same thing with dry matter basis: if I already know one is 50% DMB and the other is 45.45% DMB, you can assume 50% is higher – no need to calculate the % DMB all over again if you already have it to compare.
Example: which food is higher in phosphorus?
Food C has a phosphorus of 0.16% “as fed” with 80% moisture, and ME is 800 kcal/kg according to the food label. Food D has a phosphorus of 0.18% “as fed” with 77% moisture with ME of 1,100 kcal/kg. Which is higher?
I can’t say Food C is higher based on these “as fed” percentages, because I know they are diluted by the moisture – I need to use dry matter basis or a calorie basis (mg/100kcal – mg of phosphorus per 100 calories) to compare. Let’s compare them both ways.
According to the % DMB calculator, Food C has a phosphorus of 0.80% DMB and Food D has a phosphorus of 0.78% DMB. So on a Dry Matter Basis, Food D is actually very slightly lower in phosphorus. 0.78% DMB is less than 0.80% DMB, slightly.
What about on a calorie basis, mg/100kcal? (If you feed 100 calories of either food, from which food does your cat consume the least phosphorus?) We can calculate those too using the mg/100kcal calculator. Plug in the 0.16% and 800 kcal/kg for Food C and we get 200 mg/100kcal ; plug in the 0.18% and 1,100 kcal/kg for Food D and we get 164 mg/100kcal. So…Food D is more than just slightly lower than Food C, on a calorie basis: 164 is less than 200.
Common Terms and Definitions
Nutrient Profile
Table of nutrients, minerals, vitamins, etc. Basically – rows of numbers or percentages. There is no standard, so every pet food company might use a different format for “nutrient profile.” Some use “as fed” percentages. Some use dry matter basis. (And sometimes, a nutrient profile is a “typical analysis” (averages), other times it’s “guaranteed analysis” (minimums/maximums). Some use a calorie basis. Some use more than one! That makes it hard to compare between different brands. Just try to understand what the company is actually using.
Calories
A measure of energy from food. (Listed on a food label as “kcals.”) Calories come from three things in food: protein, fat, and carbs. Fat is more calorie-dense than the other two – contributes about 2x more calories by weight than protein or carbs. So high-fat foods are much more calorie-dense than low fat foods.
Protein and fat are always listed on the food label. Carbs almost never appear on a food label and have to be estimated separately.
Calories are a closed circle or “zero sum” if you will. More fat means less protein and/or less carbs. All the calories from the the sources of energy add up to 100% of the calories in the food.
Guaranteed Analysis
FDA requirement (in the US) – minimum and maximum percentages. Gives you a rough idea of what’s in the food but not precise enough to help you figure out things like, “Is this food low in protein?” Moisture is different in every food, and all percentages in a guaranteed analysis are on an “as fed” basis, so trying compare protein or fat by guaranteed analysis might be pointless.
Typical Analysis
Nutrient profile of average/typical values and percentages, not minimums and maximums. More accurate and much more useful than an guaranteed analysis! Typical analysis may be given “as fed” or on a dry matter basis or calorie basis…or any/all of the above. Have to get this from the manufacturer (sometimes on their website). Never on a food label.
“As Fed” basis
Percentages diluted by the water in the food “as you feed it.” Not useful for comparing foods in terms of which one your pet would consume the least/most of, of some nutrient. But useful (essential) for calculating dry matter basis and calorie basis percentages if you don’t already have them. Guaranteed analysis on a food label is always shown “as fed,” never on a dry matter basis.
Sometimes called “as received.”
Dry Matter Basis
Percentage of something in the “dry matter” part of the food (if you remove the water, the “dry matter” is what is left – e.g. if a food has 80% moisture, then it has 20% dry matter (100% – 80% = 20%). All the nutrients and minerals come from the dry matter, not from the water. So we want to know how much of say protein or phosphorus is in the dry matter, without the water diluting it. Much more useful than “as fed” for comparing foods! Can be easily calculated using the moisture and the “as fed” percentage.
Calorie Basis
Percentages (or ratios) with water factored out, based on calories fed, alternative to using dry matter basis (which is based on weight, not calories)
Minerals are usually expressed as mg/100kcal (mg of minerals per 100 calories) or g/1000kcal (grams per 1000 calories). Protein, fat, and carbs can be expressed in g/1000kcal, but are often expressed using a nifty shorthand called Metabolizable Energy (ME) Profile instead.
Can be more complicated to calculate than the dry matter basis, but some (including yours truly) prefer using a calorie basis since it seems to correspond better to how much of a nutrient or mineral a cat actually eats.
Metabolizable Energy (ME)
The “energy” of the food; calculated from a formula based on the protein, fat, and carb contents of the food. Usually expressed as kcal/kg (calories per kg), sometimes as kcal/oz. The higher the ME, the higher in calories the food is. The ME is diluted by the moisture in the food. That’s why foods wet foods (roughly 75% water) have a lower ME. than dry foods which have almost no moisture in them If two foods have the same moisture, then the one with a higher ME is higher in calories.
For example, a wet food that has an ME of 1,200 kcal/kg (1,200 calories per kg of food) would be more calorie-dense than one that that has an ME of 1,000 kcal/kg.
A dry food that has an ME of 4,000 kcal/kg would be more calorie-dense than one that is only 3,800 kcal/kg. Since dry food has very little moisture, the ME numbers are much higher than in wet foods.
ME Profile
Metabolizable Energy Profile. The calorie distribution from protein, fat, and carbs, the three things (percentages) that contribute all the calories to the food. Also called “percentage of calories” from protein (or fat, or carbs). The three percentages must add up to 100%. E.g. if protein is 40% and fat is 50%, then carbs must be 10%. You can’t have an ME Profile that is 60% protein and 50% fat and 20% carbs – those add up to more than 100%.
These percentages are not the same as dry matter basis! 30% of calories from protein does not mean 30% dry matter basis!!! And, there is no simple way to convert between dry matter basis and ME profile. A food that is 30% of calories from protein might be anywhere from 40% to 50% protein on a dry matter basis.
ME Profile is relatively easy to calculate if you have accurate percentages for protein, fat and carbs i.e. typical analysis. Carbs are sometimes the tricky one to get, since they are not always provided or easy to estimate.
mg/100kcal
mg (milligram) per 100 calories – that is, something is 100 mg/100kcal phosphorus has 100 mg of phosphorus for every 100 calories you feed.
Usually used for minerals like phosphorus, calcium, sodium, etc. as an alternative to dry matter basis. Some believe a calorie basis like mg/100kcal corresponds better to how much of the mineral your cat actually consumes vs. dry matter basis.
Easy to calculate the mg/100kcal if you have the “as fed” percentage of the mineral and the Metabolizable Energy. For example, if a food has a phosphorus of 0.2% “as fed” and a ME of 1,000 kcal/kg, just divide 0.2 by 1000 …and multiply by 1,000,000 (one million) to get the right units. (the answer is 200mg/100kcal). You can use this calculator for mg/100kcal as well.
g/1000kcal
Grams per 1000 calories – same as mg/100kcal but with different units. E.g. something that is 3 g/1000kcal (3 grams per 1000 calories) is the same as 300 mg/100kcal. Just move the decimal point two places. Sometimes it is expressed one way or the other but is the same thing, like 16 ounces being the same as 1 pound. Food companies all like to do things differently than their competitors.
Easy to convert between mg/100kcal and g/1000kcal or vice versa – move the decimal point two places.
kcals
Kcals are calories for our purposes. Purists may quibble with this and explain why they aren’t always calories…but yeah, they are, for our purposes.
g/100g
Grams per 100 gram – basically the same as a percentage. A food that has 0.2 grams per 100 gram phosphorus is just 0.2% phosphorus. Why can’t they just write it as a percentage in the first place?
g/kg
Grams per kilogram – or grams per 1,000 grams. The same as g/100g with the decimal point moved one place to the right. Why write it this way??? Who knows. But, it’s pretty easy to convert.
E.g. if a food is 1.7 g/kg…that’s the same as 0.17 g/100g…or just 0.17%.