IS MIXING DRY AND WET FOOD BAD FOR DOGS AND CATS?
I often have dog and cat owners come to my clinic saying: “Doctor, I can't mix kibble with wet food because it's bad for my pet's digestion” … Before answering this question, let’s clarify a bit about pet food technology and how both dry and wet animal foods are made.
To keep it as simple as possible, wet foods come from products that go through less complex processing; the raw material is more or less processed, canned, and sterilized. With around 70% moisture
To make kibble, however, the finely ground, homogenized product goes through an extruder—a machine that creates a very fluid mixture (similar to mousse) under high pressure and temperature, which is then cut into small pieces. These still-soft pieces are then dried to become hard and form kibble, ready to be packaged. With 8-10% moisture
We can say, therefore, that a key difference between wet and dry food lies in the water content percentage. That said, the production process for kibble necessarily requires a source of carbohydrates (usually starches), unlike wet foods.
HOW DOES DOG AND CAT DIGESTION WORK?
Once in the intestines, the primary nutrients (meat, sugars, and fats) are broken down into simple molecules (proteins, carbohydrates, and lipids) and then into even simpler molecules. This happens with all food components, whether dry or wet.
For example, just think how carbohydrates from very different foods like rice or pasta are broken down into the same glucose molecules during digestion. The same applies to protein sources, which, for instance, regardless of whether they come from lamb, chicken, or tuna, are ultimately converted into amino acids.
So the digestive process will be longer for more complex foods, but, regardless of the initial complexity of a food, the intestine will break it down into the same simple molecules through digestion so they can be absorbed.
SO, WHAT HAPPENS DIGESTIVALLY IF I MIX DRY AND WET FOOD?
As mentioned before, there’s a big difference in water content between dry and wet foods. Water is a key nutritional element, but it doesn’t cause major changes in digestion except for the speed of gastric transit. The higher the moisture, the faster food moves from the stomach to the intestine.
In healthy animals, the faster or slower passage from the stomach doesn’t cause issues, so the intestinewill receive the wet food first, then the kibble. Generally, wet foods have fewer ingredients than dry ones, so not only is their gastric transit faster, but their digestion is too.
SCIENTIFIC EVIDENCE, WHAT DO THEY SAY ABOUT A MIXED DIET?
Animals enjoy both dry and soft foods. Cats usually prefer them split into separate meals throughout the day, unlike dogs who like them together in one meal. A mixed diet is therefore not to be discouraged; instead, it combines the benefits of both.
Dry foods also promote better oral hygiene. Several studies show that, through mechanical action, they limit plaque buildup. Wet diets, on the other hand, are often more palatable and increase water intake, which is especially helpful for cats.
LASTLY, THOUGH, WATCH THE CALORIES!
I always point out, though, that when making mixed dry-wet diets we need to consider the total calories we’re giving. While it’s easy to figure out the daily portion for one type of food since it’s listed on the package tables, it’s less easy if I want to give two different foods. For this calculation, get help from your nutritionist veterinarian. Maybe soon I’ll share some “tricks” on how to do quick, simple calculations to avoid mistakes with calories if you want to mix dry and wet foods.
Dr Simone Falci
Veterinarian expert in nutrition
BIBLIOGRAPHICAL REFERENCES
*Ingham et al. 2002
**Burger et al. 1980