My distinct impression is that cat soup is a good complementary food for cats. There are two reasons why I have come to this conclusion, (1) the pet food manufacturers usually consider cat soup to be a premium product and therefore the ingredients are higher quality than average or at the top end of quality for cat food and (2) it contains more than the usual quantity of water which of course is flavoured. This encourages a cat to drink water which cat guardians always try to encourage because domestic cats are normally fairly poor drinkers.
Although, of course, the higher water content means that the product is cheaper to produce. I suspect, therefore, that the pet food manufacturers have a better profit margin on cat soup than on other products but I’m guessing.
Felix soup is considered to be a complimentary pet food and therefore is not entire and complete in terms of a diet. The sachets are quite small which I like because my cat eats all the contents. I hate to see waste. Purina recommend one pouch per day as a complement to other complete products. Other, higher quality cat soups will no doubt have a higher protein content and provide 100% complete and balanced nutrition.
In addition to providing a change in their diet (variation is important), I suspect that one of the aims of this product is to encourage drinking. For that reason alone I think it can be recommended especially for those cats who are very poor drinkers. It would certainly be a good complement to cats on dry food diets. It is not recommended to feed cats exclusively on dry food. If an owner likes to feed a cat dry food I would suggest that they add this soup as a compliment to it. It would do a lot of good to their health proactively.
The moisture content of cat soup is 87% which I would suggest is higher than normal which in turn is unsurprising because it is a soup. The Felix soup that you see in the photograph contains 7.5% protein and 1.5% fat. This is a lower protein content than is recommended by the experts. Protein content should be at least 12% by weight for an adult domestic cat to remain healthy and normally higher as mice contain 40% protein and 50% fat. Kittens need 18% protein. Dogs can survive on lower protein foods and can get by on 4 percent protein. I suspect the experts recommend a higher level.