What's in the can

A pet food label is one of the best ways to determine the quality of the food you are feeding. The ingredients and the guaranteed analysis (amounts of protein, fat, etc) are included on the food label. In addition the label will also alert you of any unwanted preservatives and give general feeding guidelines.

All pet foods have different levels of moisture. 
Canned foods can have up to 80% moisture where some dry foods can have as little as 6%. 

Calculations
If a dry food has 5% moisture we know that it has 95% dry matter. Look at the label and check the protein level that might read 20%. Next we divide the 20 percent protein by the 90% dry matter and we get 22%, which is the amount of protein on a dry matter basis.

Commercial Food 2