Anlæggets mindstemål og udformning bør afspejle det formål, hvortil dyrene holdes (avl, bestand, korte eller lange forsøg), og give mulighed for så meget inventar, at den miljømæssige kompleksitet forbedres.
The minimum dimensions and design of the enclosure should take into account the purpose for which the animals are maintained (breeding, stock, short or long experiments) and enable the inclusion of sufficient devices for improving the environmental complexity.