Guaranteed Analysis Explained

Pick up a can of wet cat food with 10% protein on the label and a bag of dry kibble showing 32%. It looks like an easy comparison. The kibble has more than three times the protein. Except it does not. Once you strip out the water, the wet food can carry 45% protein on a dry matter basis versus the kibble's 36%. The label made the kibble look better. The numbers told the opposite story.

That inversion is the most useful thing to understand about guaranteed analysis. It is not a ranking tool. It is a snapshot of nutrient minimums and maximums, taken at a specific moisture level, using measurement methods that are nearly two centuries old. Used carefully, it tells you something. Used uncritically, it misleads.

What an Australian cat food label is actually required to show

In Australia, cat food labelling is governed by Australian Standard AS 5812:2023, which covers the manufacturing and marketing of pet food for cats and dogs. Under that standard, a manufacturer is required to declare, at minimum, crude protein, crude fat, and metabolisable energy. Moisture, crude fibre, and ash are not required unless the brand makes a specific health claim that brings them into scope.

There is also a choice in how those values are presented. A brand can list them as guaranteed figures (a minimum, a maximum, or both) or as typical or average composition. A guaranteed minimum protein of 9% means the product will not fall below that figure. It does not mean the product contains exactly 9%, or that 9% is representative of what is actually in the can.

This is a looser requirement than the US system, where the Association of American Feed Control Officials mandates a fixed panel of four values (minimum crude protein, minimum crude fat, maximum crude fibre, maximum moisture) in guaranteed format. AS 5812 references AAFCO or FEDIAF nutrient profiles as the benchmark for complete and balanced claims, but the label format itself is more flexible.

A voluntary standard in a largely unregulated market

The complication is that AS 5812 is a voluntary standard. PFIAA-certified manufacturers are independently audited against it each year by AUS-MEAT, and PFIAA's own figures indicate its members account for around 70% of cat food sold in Australia. But a brand operating outside PFIAA membership faces no equivalent obligation.

There is no federal regulator with clear jurisdiction over general pet food. Food Standards Australia New Zealand covers human food. The Australian Pesticides and Veterinary Medicines Authority covers veterinary medicines. The ACCC can act on misleading conduct under Australian Consumer Law but cannot make AS 5812 a product safety standard. That gap has been in front of government for years. A 2018 Senate inquiry recommended mandatory regulation. As of 2026, the cost-benefit report commissioned to inform that decision had still not been released publicly. South Australia introduced a pet food labelling bill in its upper house in 2024, which would be the first enforceable labelling law in the country if it passes.

PFIAA itself supports mandatory regulation. So does the RSPCA and the Australian Veterinary Association. Both sides agree the standard is sound. The argument is whether it should be mandatory.

What “crude” actually means

Each figure on a guaranteed analysis panel carries the word crude. Crude protein, crude fat, crude fibre. That word is analytical, not evaluative. It describes the measurement method, not the quality of the nutrient.

Crude protein is measured by detecting total nitrogen in the sample and multiplying by a conversion factor of 6.25. The assumption is that most nitrogen in food comes from protein, and that protein is approximately 16% nitrogen. The problem is that the method counts all nitrogen, including non-protein nitrogen from free amino acids, urea, creatine, and other compounds. It also says nothing about amino acid profile, digestibility, or whether heat processing has damaged lysine or other heat-sensitive amino acids. A food with a high crude protein figure could theoretically be delivering less usable protein than a food with a lower figure.

Crude fat is extracted using a solvent and weighed. The standard method can under-report fat in processed foods because it misses some phospholipids and matrix-bound lipids. Acid hydrolysis before extraction gives a more complete result for cooked and retorted products, which is why some regulatory bodies specify it for heat-processed pet food. Whether a given product's fat figure was measured by ether extraction or acid hydrolysis is almost never disclosed on the label.

Crude fibre is the residue that survives sequential boiling in dilute acid and alkali. That process dissolves most soluble fibres, hemicelluloses, pectins, and gums. Published research comparing crude fibre to total dietary fibre in commercial pet foods found that total dietary fibre is typically two to four times higher than the crude fibre figure. For a cat owner trying to understand fermentable fibre content or gastrointestinal effects, crude fibre is a poor proxy.

The moisture problem, and the dry matter fix

The most consequential limitation of the guaranteed analysis is that every figure is expressed on an as-fed basis. That means the moisture content of the food is included in the denominator. A wet food with 78% moisture and a dry food with 10% moisture are expressing their nutrients against very different denominators. Comparing them as-fed is mathematically meaningless.

The correction is called dry matter basis. You subtract the moisture content from 100 to get the dry matter percentage, then divide the nutrient figure by that number and multiply by 100.

For a wet food with 10% crude protein and 78% moisture, the dry matter is 22%. Protein on a dry matter basis: 10 divided by 22, multiplied by 100, equals 45.5%. For a dry food with 32% crude protein and 10% moisture, the dry matter is 90%. Protein on a dry matter basis: 32 divided by 90, multiplied by 100, equals 35.6%. The wet food is the higher-protein option. The label suggested otherwise.

The US Food and Drug Administration uses exactly this example in its consumer guidance, noting that without the dry matter conversion, a cat owner would mistakenly conclude the dry food has more protein when the opposite is true.

Dry matter basis is a minimum step for cross-format comparison. It is not the final word. Nutrient density expressed per 1,000 kilocalories of metabolisable energy is more precise, because it accounts for the fact that two foods with identical dry matter protein figures can deliver different amounts of protein to a cat eating to its calorie needs. Australian labels are required to list metabolisable energy under AS 5812, though it is sometimes buried or listed in kilojoules rather than kilocalories. Where energy content is available, the per-1,000-kcal calculation is worth doing.

KibbleGuide's dry matter basis calculator runs both conversions automatically.

What ash tells you, and what the low-ash myth gets wrong

Ash is what remains after a food sample is incinerated at around 550 degrees Celsius. It represents the total mineral content, predominantly calcium and phosphorus, which together typically account for 60 to 70% of the ash mass. Magnesium, potassium, sodium, and trace minerals make up the rest.

High ash content in a cat food generally reflects higher inclusion of meat meals and bone-derived ingredients. It is not inherently negative. A food with very low ash could be under-fortified with minerals, which is a more serious concern than elevated ash from natural ingredients.

The idea that low-ash food protects against urinary tract problems is a legacy marketing claim from the 1970s and 1980s that has since been revised. Research, including Zoran (2002) and subsequent WSAVA nutrition guidelines, established that struvite crystal formation is driven by urine pH, urine concentration, and the specific form of magnesium present, not total ash content. A cat owner managing urinary health is better served by asking a manufacturer for magnesium content per 1,000 kilocalories and looking at the food's effect on urine pH than by choosing on ash percentage alone.

What the guaranteed analysis leaves out

The figures on the panel do not capture the nutrients that matter most for a cat as an obligate carnivore.

Taurine is not listed on most Australian cat food labels. Cats cannot synthesise enough from precursors and require it preformed from animal tissue. Deficiency causes dilated cardiomyopathy and central retinal degeneration, both irreversible if not caught early. Arginine is not listed either. Research published in the late 1970s showed that a single meal without arginine can produce acute hyperammonaemia in cats, with potentially fatal results within hours. Arachidonic acid, preformed vitamin A, and vitamin D are all essential for cats and absent from most labels, because cats cannot adequately synthesise them from plant precursors the way many other mammals can.

The vitamins most at risk from heat processing are also invisible on most guaranteed analysis panels. A study published in the Journal of the American Veterinary Medical Association in 2014 tested 90 commercial canned cat foods labelled complete and balanced and found that 13% were below AAFCO's minimum thiamine requirement. None of those products would have been identified as deficient from reading the guaranteed analysis.

Calcium-to-phosphorus ratio, protein digestibility, amino acid profile, energy density, and ingredient origin are all absent. The guaranteed analysis is a starting point. It does not tell you whether the food is appropriate for a cat.

Where KibbleGuide sits

KibbleGuide does not score or rank products. We publish the ingredient list, the guaranteed analysis, and where data is available, the dry matter basis protein, fat, and ash figures for every product in the database. Those are the inputs. The decision is yours.

The guaranteed analysis is useful for what it is: a partial, as-fed snapshot of a small number of nutrients, measured by approximate methods, under a voluntary standard that most Australian manufacturers follow but are not required to. Used within those limits, it is a legitimate starting point for comparing products of the same format. Used to compare wet food to dry food without conversion, or treated as a complete nutritional picture, it misleads more than it informs.

The question worth adding to your label reading is what is not there. Moisture, if not listed. Energy density, if buried or omitted. Ash and fibre, if absent. Those gaps are themselves informative. A brand that publishes a full typical analysis alongside its guaranteed minimums and maximums is telling you something different about its transparency than one that publishes only the required fields.

Related reading

• Dry Matter Basis Calculator. Run the wet-vs-dry conversion for any two products in the database.
• Why Your Cat Cannot Just Eat Anything. The peer-reviewed research on feline nutrition that explains why taurine, arginine, and arachidonic acid are not optional.
• The Label Guide. How to read the ingredient list once you understand what the numbers behind it can and cannot tell you.

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