Welcome to Yorkietalk! All dogs are sensitive to certain foods especially the first year, and any change in the diet can cause loose stools, so food changes should be very slow. Most dog treats are not even that good for a small breed dog, because what is a treat for some dogs, is an entire meal for a Yorkie, and so even a treat can cause intestinal problems. We used Cheerios, the first year with Joey, they were small enough not to interfere with his appetite, yet helped to reinforce certain behaviors, such as success in housebreaking, and patience while being groomed. Yorkietalk is a great place to learn lots of little things that a good yorkie mom should know. I think the thing that surprised me the most was that one piece of certain types sugarless gum could kill a dog, and that first year, they will eat anything! You might want to check out this list.
http://www.yorkietalk.com/forums/yor...oods-dogs.html