There are many situations in which a veterinarian might ask you for details about the pet food that you're currently feeding your dog. Read on if you're curious as to why your vet might ask this type of question.
The dog has persistent gastrointestinal issues
Dogs will often have occasional bouts of gastrointestinal problems; oftentimes, their upset stomach is the result of them eating an inedible object or getting a bacterial infection. The former will often resolve itself when the dog passes the object in question, whilst the latter can usually be cleared up with some antibiotics. However, if your dog has persistent gastrointestinal issues that don't appear to be caused by the consumption of inedible items and which have not been resolved after a round of antibiotics, the vet might decide to take a closer look at the pet food you feed them.
The reason for this is as follows; whilst a dog will eat almost any type of food, this does not mean that it is safe for them to do this. In a situation like this, the vet might be worried that some of the food that you're giving your pet is not suitable for them. For example, if addition to feeding them kibble, you are supplementing their diet with the leftover 'human' foods that you and your family eat each day, then is possible that some of the items in these leftovers are adversely affecting your dog's digestive system. For example, if these leftovers contain small amounts of grapes or garlic, then these could be the cause of your dog's frequently upset stomach, as these foods are all toxic to dogs. In this situation, the vet might advise you to immediately stop giving your dog any human food and to instead stick strictly to kibble and other foods that are designed specifically for dogs.
The dog appears to be allergic to something
If your dog is showing signs of being allergic to something (for example, if they seem to feel very itchy and are scratching themselves, even though they do not have fleas) and your vet has ruled out the possibility of your pet being allergic to some environmental allergen (like pollen), then the next step they will take is to find out what pet food they are eating, as it is possible that they might be intolerant to some ingredient in this food (even if the pet food you buy contains ingredients that are generally considered safe for dogs to eat). For example, some dogs are allergic to specific meats, like chicken or beef. As such, your vet might suggest that you eliminate one type of meat from your pet's diet for a specific period; if this results in the allergy symptoms subsiding, then they may recommend that you permanently exclude that particular meat from the dog's diet.