LucyImHome, the amount of water depends on the brand of food you buy. Any canned food will have water, but the higher quality brands have much less water compared to less expensive brands.
I used to have an aversion to canned dog food. Why or how I developed a general aversion to it, I don't know, but I did. When I started considering it, I became aware of my baseless opinion and set out to see if it had merit. It didn't.
I changed for three reasons. First, my dog has extremely bad hips and a deformed back. My vet said she probably wouldn't live past 10. At 9 she was starting to display pain and discomfort much more frequently, so higher and higher quality food was fed to her until I found the best food I could buy. When I realized the canned form was that much better, I opted for that. Several people have commented how she is doing better. People who've never met her constantly comment on how frisky and bouncy she is for an 11-year-old dog. Many think she is still near the puppy stage, but with her greying face, that is less common. I can't say for certain increasing the quality of her food helps, but a strong correlation is there.
Secondly, dry food goes stale after about two weeks. A 27 pound bag would last me about 5 weeks; at that point I could notice a considerable change in the food. (I always folded the bag over and used a heavy duty wood working clip it shut. I never dumped the bag into another container.) I couldn't see it becoming rancid or moldy, but clearly stale. I then started buying 13 pound bags, but dry dog food gets more expensive the smaller bags get. Since the smaller bags started approaching the cost of canned, the cans began looking more financially appealing.
The third reason is the carbohydrate/protein/fat ratios are much better than dry kibble. In order for kibble to not be dust, it needs some type of carb to keep it in kibble form. Dogs aren't ideally built to handle a lot of carbs. Carbs are an easy way to gain weight, too. My dog doesn't have a weight problem, but the weight thing is good to know. I don't want her to develop a pooch like her dad.
Kidney stones are something to be aware of. Not as much of a concern for dogs, but more so for certain breeds of kitties. (Yes, I call them "kitties" not "cats" because "kitties" is much cuter. I can't help it!) Kidney stones form when the urine is too acid or too base and there are enough minerals in a solution (urine) that is not diluted enough. To help prevent kidney stones, I keep my dog well hydrated. Canned food helps with that. Less water concentrates any minerals that are present which makes crystallization of the minerals more likely to occur. The process of making dry food inherently increases the amount of minerals like phosphate and magnesium. Canned food isn't "cooked" like dry food is, so fewer crystal-forming minerals are created. If the minerals aren't there in the first place, crystals in the kidneys won't develop because you can't create crystals out of thin urine... I mean thin air. Prescription foods from Science Diet have differing ph levels and reduced mineral content in their food to help prevent kidney stones. Sometimes spending the extra money for a high quality canned food will solve the problem without needing the more expensive yet lesser quality prescription food, but that should be done on the advice of a veterinarian. Kidney stones are very serious. And kidney stones are sooo painful. Not to sound gross, but peeing out a kidney stone is awful!
Canned food is definitely more expensive than dry and it can be hard to measure. My dog uses 1 1/2 cans of food per day. I place the half can of food in the fridge for the next day. If you use an odd ratio like 5/6 of a can, then that can be a pain to measure. My dog used to hate the canned, but now she prefers it much more than the dry. The food I use smells good. If I used it to make hors doeuvres, you wouldn't be able to tell.
When I said she drinks close to a third less water, that estimation seems exaggerated. Definitely less than half, though- a considerable difference in water consumption.
