Bull Terrier
Interbreeding, the process of mating together a Miniature Bull Terrier and Bull Terrier, is allowed, but only for a short time, in Australia, New Zealand, and the United Kingdom. Interbreeding is undertaken to reduce the incidence of Primary Lens Luxation in the Miniature. The Bull Terrier does not carry the PLL gene, so all progeny are phenotypically normal for the disease.