Is it sometimes the dogs are not fit and after chase they blowing from they arse it will be a lot harder to kill then . And some dogs just make hard work of it and in the end they don't want it and dont put it all in at the final end were the fox should be caught and most will say that the dog missed it but really if you look hard you will see they don't want it I wouldn't keep one but many do they must be hungry to kill at all times