Question

Which is a disadvantage of inbreeding?

Answer 1

Inbreeding would be an option if a breeder
a) had a very limited stock of the purebred breed
b) wanted to magnify a specific trait

but disadvantages would be
a) a risk for expression (physical manifestation) of double-recessive or semi recessive traits that would aversely affect the offspring--an example of this would be the hip problems many dog breeds have developed over the centuries of selective breeding
b) further concentration of an already concentrated breed.

Physical deformation and mental disability aren't necessarily outcomes with inbreeding, but given enough inbreeding, they are definitely risks. Nature favours diversity!!