Obviously your new pup needs food, but Dr. Richardson recommends you start your puppy on whatever food they were eating before. If the shelter or previous family was feeding them a specific brand, feed them the same stuff, then wean them onto a different food of your choosing. "If you would like to change the food after the initial settling-in period, do so gradually by mixing the new food with the old food over the course of five to seven days," she told POPSUGAR.