Brood units are stores of genetic material intended to be used to grow new lifeforms. They are often used by species concerned about their survival, in order to ensure that they will not be totally eradicated. Brood units are also used by the Auronar in their cloning process.
The rocket that Meegat watched over contained brood units that would automatically develop into life upon arrival at their destination. The Liberator also encountered a rocket containing brood units on its way to Saurian Major -- these brood units could develop into a life form in 1.6 minutes.
Brood units are derived from Blake's 7.