IF You buy a complete food rather than a "dry food "

there is no reason to add anything to it.By doing so you unbalance the nutritional value and your dog will come to expect
Something added to his food every time,Start as you mean to go on what ever food you buy put it down for 10-15 min if your dog does not eat it in that time remove and repeat this at each meal time, you will so find that the dog gets the message that its time to eat -Jo