Dog doesnt eat sometimes?

i have a fussy border collie and some days he can go 2 days without touching a thing! i used to panic all the time but what i've found is on the days he's not eating i take him to my mums for a bit and feed him with her dogs he soon eats all his food then because he has competition and doesnt want the others to eat his food. i also have found that he doesn't like dog biscuits so now i leave them out it's better than waste hope this helps just a little :)