Let's add to the controversy.
If you're not planning on selling any of the weaners to people who would want to breed, then there is no reason why you need to register. You could quite happily sell the weaners from your unregistered OSBs as OSB type weaners to people who want meat pigs.
This is no different to selling puppies from dogs who are not registered with the kennel club.
The vast majority of purchasers of our weaners simply want meat pigs, so don't care whether mums are registered or not, they look for conformation, health and attractive looking pigs - in fact many of our crossbreds sell better than the purebreds as they mixing throw really interestingly marked pigs.