There are several reasons why you might need to switch the food your dog is currently eating for another. It could be that your pup needs to make dietary changes due to age, perhaps his vet has suggested the change, or maybe he simply refuses to eat the food you are trying to feed him. Yes, this can happen, some dogs seem to just get sick of a particular food or it might have started to upset his tummy.
The good news is that in most cases, the transition is a relatively easy process and takes minimal training, it is more a matter of patience. The most important thing you can do is try and plan the training ahead of time. Remember, you cannot simply take your pup's old food away and suddenly dump a new one in his bowl. Doing this may result in your dog refusing to eat or suffering from nausea, diarrhea, or vomiting.
The task at hand is to transition your dog from one brand or type of dog food to another. No matter why you are making the change, it has to be done the right way or you may end up with a very sick pup. While you might feel like you need to be in a hurry, especially if the current food is making your pup sick, this training is more a process than anything.
It takes several days, and you should not try to shorten it as you could end up with a very sick dog. You should not expect to see the desired results for at least 7 to 10 days after the change has been completed.
For this training, you will need very little in the way of supplies, just some of the old food and some of the new food. If your pup is having trouble with his current food, such as an upset tummy or diarrhea, you should take him to his vet for an examination before making any changes to your pup's diet. Beyond this, be sure to match the new food to your dog's age in order to ensure he is going to get the right nutrition. If you are not sure about the food you are considering changing your dog to, your vet can advise you.