I have had much successful feeding my terrier, a Westie, by the name of Chica Marika, Nature's Valley RAW Dog Food Medallions. Her hair is shiny, coarser and beautiful, eyes bright, nose black, ears in excellent shape and the best thing of all.......LESS waste at the end of the day. If you know what I mean.
Just like Yorkie's, Westies have very sensitive stomachs. You can't feed them rich dog food, as it will upset their tummies and you can't give them particular treats for the same reason.
Chica is 19lbs and she receives 6 medallions a day. Twice a week, she gets a raw egg in her breakfast.
Her vet said she is the healthiest Westie's she has seen in a loooonnnggg time. Keep in a mind: a raw food diet also produces a great deal of energy.