Greetings & welcome to the forum,
Just a few questions to help get a picture...
How often are you feeding him and how much?
How long has he been off his food?
Since you've had him from his litter, has he ever eaten a regular amount or has he been picky/not eating since you've got him?
Is he on the same food that the breeder reccommended and he was used to?
Blunt questions, but it does help to understand how dire his hunger strike is :) He's a very small dog and might not need as much as you think he does.
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We're friendly and don't bite (might snarl occasionally, but that's about it :D )
regards,
toodles