Worked example of intermittent breeding

Intermittent breeding should be used instead of constant mating to avoid unnecessary wastage of animals, whilst retaining the ability to breed an experimental cohort immediately. The use of intermittent breeding will depend on the breeding performance of the strain (e.g. litter size, reproductive lifecycle, fertility etc), for example, backcross colonies (both those that are congenic and those that are in the process of changing background and may not be congenic yet) can usually be held comfortably with intermittent breeding.  

Below is a worked example describing an intermittent breeding strategy for keeping breeding stock available for 6 homozygous females, 6 homozygous males, 6 wild type female and 6 wild type males, using C57BL/6N breeding stock.