What is the UKC age breeding standard?

My husband and I own an APBT registered with UKC and she is purple ribbon bred, 'PR' Notorious Kitta. I went to the UKC web site and still could not find what the age limit they accept puppies from. She recently turned 6 years old and has never had a litter before. She is the last of her champion and grand champion bloodline and we would hate for it to end with her. We have wanted to breed her before but were unable due to housing situation and lack of a great stud and we are just now able to do this. So wold they not accept puppy registration from her cus she is 6 or should we look around breeders and buy a new puppy and jus wait and breed it?