It is understandable that once a breed is added to the banned breeds list, all living examples deemed fit and proper for an exemption certificate must not be able to reproduce.
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To obtain a certificate of exemption, the dogs must be neutered to prevent future reproduction. Currently, this is achieved by removing the sexual organs, I believe with no consideration to the health and welfare of the dogs.
Allow breeds that are banned under the Dangerous Dogs Act to have hormone sparing sterilisation. Some studies have shown that hormone sparing sterilisation (vasectomy / hysterectomy) can prevent multiple health issues. These alternative methods still achieve sterility.