Like the labels on food consumed by humans, a pet food label is subject to standards set by the government. While the national standards set by the FDA are mainly concerned with how the ingredients are represented on the pet food label, most states have standards in place for listing nutrient content.
First, the pet food label typically includes a guaranteed analysis. A guaranteed analysis expresses the nutrient content of the food as percentages and includes:
- The minimum amount of protein
- The minimum amount of fat
- The maximum amount of fiber
- The maximum amount of moisture
The labeling requirements are only for products intended to provide fat, protein or fiber, so supplements and vitamins are not subject to the requirements.
Canned and dry pet foods have very different amounts of moisture, which can make comparing nutrients of dry food to canned food tricky. The easiest way to compare them is to multiply the protein, fat and fiber content of the canned food by four. This will usually give you a good estimation of what the nutrient percentages would be if the canned food was reduced to the same moisture content as the dry food.
To do an exact comparison of the nutrient content between dry and canned food, you need to determine the ratio of the nutrient (protein, fat or fiber) to the total moisture-free content of the food. The total moisture-free content of the food can be found by subtracting the moisture amount from 100 percent. This method is needed to compare canned foods with significantly different moisture content.
You also should keep in mind that canned foods with more moisture content will tend to have a lower quantity of the dry nutrients. Canned foods often have an extra-large amount of moisture content if they include "stew," "in sauce", or similar terminology in their titles.