For pet foods, many different ingredients are often used, some for nutrition purposes, some for palatability.
The same ingredients can be used both for dry and semi-moist pet food and for wet pet food, but the ratios of protein, fat, and fibre may vary. A typical can of ordinary cat food reportedly contains about 45 - 50% meat or poultry by-products. The main difference between the types of food is the water content. It is impossible to directly compare labels from different kinds of food without a mathematical conversion to "dry matter basis."