Hi there, you might get more answers if you start a thread in this forum:
Yorkie Health & Diet - YorkieTalk.com Forums - Yorkshire Terrier Community
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Some smaller Yorkies really don't eat much, but I personally don't have too much experience on one that only eats well at one meal. Mine are hungry all the time, but we recently switched to Acana Grasslands & they love it!
I did have to entice Mimi to eat when she was younger. I tried all kinds of things: scrambles eggs, hard boiled eggs, boiled chicken breast, salmon, pumpkin, baked sweet potato. She'll eat it for a couple of days & she would turn her nose on it, then I had to think of something else to mix into her food.
Now, she eats the Acana very well, w/nothing on it, but I do mix in some diced thawed frozen green beans for breakfast & Coco Therapy oil for dinner.