A few questions will usually identify or rule out a problem with the food itself. If the owner purchases 40 pound bags of kibble for a 10 pound dog, the food is either losing its appeal at best, or at worst, starting to turn rancid. Dry food remains fresh for about one month after the bag is opened. It stays fresher in a tightly closed bag or container. Canned food is only good for about 3-5 days after opening if it is kept refrigerated.
Most dogs readily accept new foods, but if the type of food was recently changed, the dog may truly prefer the old variety. Trying the previous food again will determine if this is the case. Environmental factors can play a role too. If it’s too cold or hot, the aroma (or lack thereof) of the food may not be enticing the pet to eat.
Once I’ve ruled out a problem with the food, I’m left with the possibility of a medical problem. Unless the answer is readily apparent on a physical examination (e.g., an oral tumor), I next recommend a complete blood profile, urinalysis, and fecal examination to rule out diseases that affect the taste and smell of foods. Conditions such as kidney disease, inflammatory bowel disease (IBD), and liver disorders can reduce the dog’s sense of smell and taste (extrapolated from studies in humans and expected to hold true for dogs as well), but any disease that makes a pet feel nauseous or weak can reduce his desire to eat. Most conditions can be identified through some combination of a good physical examination, lab work, and imaging studies (e.g., X-rays or ultrasound).
Once a medical problem is identified and treatment started, how can you make food more appealing to your dog? Warming it to body temperature (about 100 degrees Fahrenheit) using a microwave or warm water will increase its aroma, but take care not to overdo it and burn the dog’s mouth. Serving the meal right after an enjoyable activity, like a walk, hand feeding, and praising the dog after he takes a bite may also help encourage him to eat.
If a dog just won’t eat a particular food, try a different brand or formulation. Older dogs (over 7 years of age) may enjoy a senior diet as these foods are made to be more palatable for dogs that may have a reduced sense of smell. You can also try adding small amounts of other foods to encourage him to eat. Adding a small amount of syrup, honey, or salt-free chicken broth may entice him. Fruits and veggies are also good additives, but avoid grapes, raisins, and onions, which can be toxic.
If none of these recommendations do the trick, talk to your veterinarian. Some dogs need the help of an appetite stimulant or feeding tube as they recover and regain their appetites.