I have try a various of dry dog food and cesar also but louis is a maltese does not want to eat at all?

He will rather don't eat for one day.then i try let him eat boneless chicken meat and some rice.And he eat it all finish,so now i try adding some vegetables and carrot,anyway and once he eat these food,he Poo Poo also everyday unlike last time haven't start eat vegetables he Poo Poo every two days.but his age is quite old and i will let him eat as long as he is happy and every two meal is full.