Is your cat’s food any good?

An obligate carnivore

This is the first thing to keep in mind when reading a cat food label. A cat needs plenty of animal protein, because it also uses it as a source of energy and cannot save it when it runs short. It needs taurine, an amino acid it barely makes and whose lack damages the heart and the retina. And it does not need carbohydrates: it tolerates them to some extent, but makes worse use of them than a dog or a person. So the question is not only how much protein it contains, but where it comes from and how much filler comes with it.

Why everything on a dry matter basis

Because it is the only way to compare. A dry food has around eight per cent water and a tin, around eighty. A tin with ten per cent protein and a dry food with thirty-two may in fact contain almost the same, or the tin quite a lot more. To take water out of the equation, each figure is divided by the part that is not water: with eighty per cent moisture, that ten per cent protein is fifty on a dry matter basis. This tool does the sum for you.

The carbohydrates that do not appear

The label does not have to declare them, but they can be estimated by subtraction. From a hundred you take away the protein, fat, fibre, ash and moisture, and what is left is the nitrogen-free extract, which is mostly starch. In a dry food it usually comes out at between twenty and forty per cent on a dry matter basis, because kibble needs starch to hold its shape; in a good tin, quite a lot less. It is not poison, but in a neutered indoor cat that tends to put on weight it is one of the numbers most worth looking at.

Tricks in the ingredient list

Ingredients are listed by weight before cooking, so fresh meat, which is almost all water, comes first even if in the end it weighs less. Splitting means dividing one ingredient into several (corn, corn gluten, corn flour) so that none of them reaches the top spot. And concentrated plant protein, such as corn gluten or pea protein, raises the crude protein figure without being meat. On the label of a good complete cat food, the first thing is named meat or fish and taurine appears among the additives.

What says nothing

Premium, natural, holistic or superior quality are not regulated and do not mean anything specific. Grain-free does not guarantee fewer carbohydrates either: peas or potato often replace the grain. What does commit the manufacturer is declaring that it is a complete food, formulated according to the FEDIAF guidelines, and for which life stage. And a tin that says complementary means it should not be its only food, even if it looks like it.