A breeding planet was a planet utilised by a spacefaring species for the sole function of procreation. The Adipose maintained breeding planets, as their young were created parasitically by injecting seed into animals. Adipose 3 was such a planet, and after it was lost they tried to convert Earth into one. This attempt failed, though many Adipose children were created. (TV: Partners in Crime) The Wirrn had breeding colonies throughout the Andromeda Galaxy, until they were destroyed by human colonists. (TV: The Ark in Space)