ive just had my bullmastiff castrated 4 days ago he had been licking the wound and it has green discharge from it also where his testicles were it looks like he has one big ball the size of a grapefruit.is this normal.

Swelling equivalent to a good size set of balls is quite normal, the green discharge would worry me that he has got the wound infected.  Are you using an elizabethan collar.  I would get him back to the vet, as if he wasn't given them after the op then he may need some antibiotics, and you should use the lampshade collar to stop him being able to lick the wound anymore.

Green discharge? No, that is not normal from a wound. I would get him to the vet for a check-up straight away (this afternoon).