
As others have said pups have to be six months to go into a venue holding an open show,however at the majority no one checks and I have on several occassions seen members of the public wander in with pet dogs unchallenged.
At kc agility shows pups have to be 16 weeks old,but this is often flouted,and all dogs have to be either on the kc breed register or on the activities register.The main difference between agility shows and breed shows is that any dog,whether pedigree or not can be put on the activities register for a one off payment of£12(it may be more now) and from then one enter any show venue for free, whereas at breed shows nfc dogs have to pay a substansial fee at each show they attend.
The kc would probably say that this is to pay for the extra benching,at champ shows,but in my breeds no one ever uses the benching,except for crufts of course and I think it very unfair that all my dogs can accompany my to agility shows but I have to leave some behind when showing as the cost makes it impossible to take the same well behaved dogs along too.
Must add that personally I would never take a pup to an open breed show under the age of six months for no reason other than I think it is very unfair to place the organisers in a posistion for which they could be fined and face disciplinary action and we need to cherish the open shows available as they are getting fewer all the time!