my 6 yr old border collie has started playing around with his dried food he stares at it then tries to hide it by pushing it under the radiator or covering it with anything around if i stay with him and keep talking to him asking him to eat he has the odd one or two taking the green ones out with his mouth and spitting them on the floor. i think he must not like it yet if i feed him with my hands he eats it what do i do