It is a very common issue with Danes, although certainly not limited to the breed, to experience picky eaters. It often starts around a year old (give/take) as their calorie needs have slowed. The owner tries all sorts of things to get the dog to eat…switching brands of food, adding tasty things to the food, hand feeding, etc. The problem is this all makes it worse! We exacerbate the issue and start the dog on a life (or at least many years) of being a picky eater. Not to mention, LOTS of owner frustration!
First, make sure there is nothing medically wrong with the dog. Any symptoms like vomiting, diarrhea, lethargic, etc. would definitely warrant an immediate vet visit. But a vet visit might be needed regardless, to rule out dental or tonsil issues.
Next, determine if the dog’s weight is truly a problem. If your dog is too heavy, or even at an ideal weight, LISTEN to them and cut back what you are feeding. Especially if they are a young adult, it is likely you are simply over feeding.
If the dog is too thin, some ideas to get them eating. Assuming you are already using a quality food, there is no need to switch foods. You need scheduled feeding times. Ideally twice a day. No free feeding. Cut out the treats for now (unless in a training class), except for right before meal time. Give a little snack to get the stomach juices going. The pre-meal snack before a meal has been a big success for me. Although it seems counterintuitive, cut back what you are offering by half. Put the food down for 5-10 minutes and then pick it back up until the next meal. If they don’t finish the meal, they get the rest of it (no more added) for the next meal. If they still cannot finish the half portion on a routine basis, cut back even more. Once they learn to clean the bowl, then gradually increase the amount until they are eating an appropriate amount.
Try to remain calm after uneaten meals. Even once the eating habits improve, the dog might still turn down a meal. Keep in mind that caloric needs can fluctuate based on age, seasons, exercise levels, etc., so there is no need to fret from an uneaten meal.
Eventually most dogs tend to age out of picky eating habits. If you utilize the above methods, you’ll save yourself lots of frustrations though.