A guaranteed analysis needs to be written on all (pet) food products, this is a legal requirement in most -if not all- countries. When comparing different feeds, one must pay attention to comparing apples to apples and oranges to oranges. Guaranteed analyses mentioned on dry feeds such as flakes or pellets, will be completely different to those mentioned on frozen or canned feeds. This is because the guaranteed amounts are declared or expressed on an ‘as packaged’, ‘as fed’ or ‘as is’ basis. Dry foods (flakes, pellets & freeze-dried), semi-moist (canned and live) and moist feeds (frozen) have very different moisture contents and as such their nutrient levels (for example of proteins, fat, fiber, ash etc.) will be entirely different. So before comparing these nutrient levels one must compare these by expressing them on the same moisture content.

Example

Let us take 2 hypothetical products, e.g. one frozen product and one flake product, with each product showing a guaranteed analysis as labeled in the following table.

AS LABELED
Nutrient	Frozen Product	Flake Product
Crude Protein	Min.     4.5 %	Min.  43.0 %
Crude Fat	Min.    0.4 %	Min.    3.0 %
Crude Fiber	Max.    0.5 %	Max.   3.0 %
Ash	Max.   0.8 %	Max. 10.0 %
Moisture	Max. 93.0 %	Max.   8.0 %

What do these numbers actually mean? Well, would one go through the trouble of taking 100 g of the frozen product and sending it to a certified lab (certified to analyze the nutritional composition of foods), the lab would measure at least 4.5 g of proteins in 100 g of the frozen product, so 4.5%. Would one send out 100 g of the flake product, the lab would say the flakes to contain a minimum of 43 g of proteins per 100 g, so 43%.

At first sight it looks like the flake product has a vastly higher protein content (namely 43.0%) compared to that of the frozen product (4.5%); it is almost 10 times higher! What is the cause of this large difference? Answer: the moisture level. The frozen product has a moisture level of 93.0% (which is why it is classified as a moist product) versus 8.0% for the flake, which is why that product is classified as a dry product. Should one want to compare the relative protein level of both products (as well as those of the other nutrients), these levels will need to be expressed on an equal dry weight basis (so on the same moisture level of 0%). In this example this will be 7% for the frozen product as the amount of dry weight equals 100% minus the labeled moisture level (so dry weight = 100% – 93.0% = 7%) and 92% for the flake product (dry weight = 100% - 8.0% = 92%). We then divide the weight of proteins (4.5 g) by the amount of dry weight (7 g) and arrive at 0.6429 or ±64.3%, meaning that 64.3% of the dry weight in the frozen product consists of proteins. When making the calculations for both products we arrive at the results depicted in the following table.

EXPRESSED AS % OF DRY WEIGHT
Nutrient	Frozen Product	Flake Product
Crude Protein	Min.  64.3 %	Min.  43.0 %
Crude Fat	Min.    5.7 %	Min.    3.0 %
Crude Fiber	Max.   7.2 %	Max.   3.0 %
Ash	Max.   11.5 %	Max. 10.0 %
Sum	88.7 %	59.0 %

When comparing both products on the same moisture basis, the frozen product turns out to contain almost 50% more proteins as compared to the flake product, namely 64.3% versus 43.0%! What is causing this? Again, the answer is not difficult to find. When adding up the amounts of protein, fat, fiber, and ash, we arrive at 88.7% for the frozen product but only 59.0% for the flake product. Why don’t these numbers add up to 100% for each product? The reason is that carbohydrates are not included in the labeling, should the percentage of carbohydrates be included the sum of the labeled nutrient amounts would add up to close to or around 100%; see following table.

EXPRESSED AS % OF DRY WEIGHT
Nutrient	Frozen Product	Flake Product
Crude Protein	Min.  64.3 %	Min.  43.0 %
Crude Fat	Min.    5.7 %	Min.    3.0 %
Crude Fiber	Max.   7.1 %	Max.   3.0 %
Ash	Max. 11.5 %	Max. 10.0 %
Carbohydrates	Min.  11.4 %	Min.  41.0 %
Sum	100 %	100 %

So why does the flake product contain a substantially higher amount of carbohy-drates? Because bulking agents or fillers (e.g. soy meal, fishmeal, soy flour, wheat flour, oat flour, rice flour etc.) are commonly used in the industry both for technical as well as cost-control reasons when manufacturing flakes or pellets. These commercially available protein sources are rich in protein but are also quite rich in carbohydrates, as nearly all are derived from plants or plant parts (except for fishmeal of course). The adding of plant-based fillers increases the amount of carbohydrates so percentage wise, the amounts of proteins, fat, fiber, and ash will decrease.

Generally said, most cold-water fish and all carnivorous fish are not well able in metabolizing complex carbohydrates as they don’t have the required enzymes for utilizing the carbohydrates derived from terrestrial plants. Omnivorous and herbivorous fish on the other hand are better equipped to handle complex carbohydrates, which is natural when considering that aquatic plants form a part of the diet of these fish. So unless one is feeding this particular flake product to either omnivorous of herbivorous fish, fish would not be able to utilize around 40% of the nutrients available in this product.

High Moisture Content

Some people might have a problem with the high moisture content, thinking: why should I pay for water? Well, because the guaranteed analysis on a food or feed only tells a part of the story. For example, the USDA has found raw apples with skin to have an average moisture content of around 85.5% and a dry matter content of around 14.5%[1]. Most of this dry matter existed of carbohydrates, namely 13.8%. This high level of carbohydrates is caused mainly by the presence of the sugars fructose, glucose and sucrose. So, are apples not nutritious because they have a high moisture content? Of course not, apples contain other compounds such as minerals, vitamins, and antioxidants such as carotene, cryptoxanthin etc. which our body requires.

Or take boiled and drained carrots, which were found to have an average moisture content of just over 90%. Carrots remain a nutritious vegetable even when having a moisture content of 90% after having been boiled. A food or feed having a high moisture content is not necessarily a bad thing as discussed in the next paragraph.

Nutrient Density

This brings us to the concept of nutrient density. Basically said, this term refers to the amount of nutrients a food or feed contains per weight unit. A nutrient is any compound a living being requires for maintaining its metabolism, its ability to grow, to repair damage, and to reproduce. Note that this is not related with the term energy density, which means the weight of calories a certain food has per volume or weight unit. Fruit and vegetables have a high nutrient density, but a low energy density. A bowl of sugar or a glass of corn oil has a low nutrient density, but a high energy density.

We do not use fillers in our line of frozen single ingredient foods, although we do use some gums as a thickener in nearly all our single ingredient items.