
Maybe it's one of those "i've gone off this food" things. Have you tried him with something else?
I have also heard and i KNOW THIS IS GROSS... that horse manure can get back an appretite but dont go feeding him that...it's just a bit of useless information!
Try him with something else like chicken and rice or something to get something inside him.
I do worry when my dog doesn't eat because he usually gulps his food down but I know for a fact that one reason was because he was bored with his food.
You would be bored if someone fed you the same meal day in day out since you were little. Wouldn't you?
If he is not showing any other signs of illness chances are it's jus a boredom thing with food. You know your own dog obviously so if you are happy with him otherwise just try a food change.
Hope this helps.
x