Should cats eat dry food?

Compared to a premium wet food or raw food diet, no. Although, a high quality dry food which is free of grains such as Orijen, Felidae and Applaws are far better than lower-quality dry foods.

Unfortunately many, many dry cat food brands are not very good for the cat in the way of nutrition; dry foods and low-quality wet foods are often packed with carbohydrates - "filler" in the way of corns and grains, none of which cats can digest. Grain is used instead of meat because it is cheaper to produce and helps the kibble pieces hold together. So much difficultly digestible carbohydrates can cause a cat to vomit or have loose stool, or it is simply stored as fat. Some obese cats have gotten that way because of low-quality dry food.

A good quality wet food (high in Meat content and grain free such as Felidae, Blue Buffalo, Wellness, Eagle Pack etc.) is far better for a cat as far as nutrition is concerned. Cats are strict carnivores, so get all their energy from Protein and Fat which is abundant in meat. Premium wet foods contain quality meat sources and no grain. Another thing wet food has an advantage has over dry food is the moisture content.

Dry food contains no moisture, so is quite dehydrating. Cats are notoriously bad drinkers, even when they are thirsty. This is because they have evolved to get all their needed moisture from their prey (their ancestors were cats that lived in very dry and arid environments where water was hard to come by), so therefore have a low "thirst drive" and will not often seek out water on their own. This is a trait that has been passed down over the thousands of years.

Canned or pouched food has anywhere between 60 to 80% water. Seeing as in the wild a cat's prey is around 65%-75% water, wet food provides a cat with more than enough water each day.

Many dry foods and low-quality wet foods are often packed with carbohydrates - "filler" in the way of grains and cereals, none of which cats can digest or gain any nutrients from. Grain is used instead of meat because it is cheaper to produce and helps kibble pieces hold together. Cats need MEAT based protein, not PLANT based protein.

Lastly, it is not proven that dry food cleans a cat's teeth. Kibble is hard and brittle, so shatters at the tips of the teeth - providing little or no cleaning friction. Dental issues usually start under or around the gumline, so kibble is usually ineffective. Some cats don't even chew; they will just swallow the kibble whole. However, some cats will have perfect teeth no matter what food they eat, while others will not benefit at all.

To clean a cat's teeth effectively, you could brush your cat's teeth with a pet toothbrush and paste, or serve pieces of raw chicken. Chewing raw meat uses the whole tooth and massages the gums and is said to be the most effective way of keeping good dental health.

All in all, you could feed both wet and dry, but dry food only really serves as a convenience to us, and provides very little for your cat. There are some decent dry foods out there that are free of grains and have a good meat source, but even that will never compare to the nutrition of canned food.