Not too many dogs don't love canned food. Wet food like this should be served at room temperature, rather than cold; and it doesn't stay good forever -- if your dog doesn't eat it all, you have to discard leftovers after a certain amount of time. This isn't just because the food goes bad, though. It's also a matter of establishing healthy eating habits and developing a routine.
Setting a Routine
You should feed your adult dog on a set schedule of twice per day -- once in the morning and once in the evening. Younger dogs need feeding more frequently, and geriatric ones may need one meal a day or several. Try to keep feedings around the same time each day, no matter how many daily feedings you administer, as dogs thrive on routines and consistency. A routine like this reminds your dog that you set the rules and helps you predict when bathroom breaks are necessary.
Leaving It Out
If you feed your dog wet food, don't let it stay out all day. Leave it out for about 20 minutes, then throw the rest away. Generally, he won't let any go to waste if he can help it. Tossing the food after 20 minutes helps prevent overeating and prevents it from spoiling in his dish. Like any other unwrapped food, the longer you leave it sitting out, the more spoilage occurs -- refrigerate the leftovers as soon as possible. If you leave it sitting out more than an hour or so, play it safe and pitch it.
Saving the Food
Not all dogs can or should eat an entire can of wet food in a single meal. When that's the case, you don't have to throw out the leftovers. Scoop out however much your dog should be eating from the can, then cover the can and refrigerate it until the next meal. You can cover it with cellophane or aluminum foil, or you can buy a special plastic lid that snaps in place on aluminum cans. When it's time to eat again, take out the food ahead of time so it can come up to room temperature. If the can itself doesn't specify how long it will keep once refrigerated, throw it out or use it after one or two days.
Transitioning Between Foods
Canned wet food is not for every dog. Some dogs prefer the crunch of dry food, which may be more satisfying for their teeth and gums -- it also helps keep their mouths cleaner. Other dogs may dislike the water content of wet food, which can help prevent dehydration but changes the texture. If you find yourself throwing away big portions every time feeding ends, consider switching brands or flavors, or feeding dry food alone. Make the transition slowly and carefully by mixing increasingly larger portions of dry food in with the wet food over a one- or two-week period. If your dog isn't eating anything you give him, make an appointment with your veterinarian