When official veterinarians or inspectors perform animal welfare inspections on farms or at slaughterhouses, they follow a checklist tied to the EU and/or national legal requirements, often specified for the specific species and stage of production. During such an animal welfare inspection, different parameters are chosen as indicators of animal welfare, and the sum of those is considered the overall welfare status of the flock.

Useful definitions:

Indicator: an occurrence, observation, record, or measurement which has a proven relationship with the legal requirement, which can be: 

- Animal-based indicator (ABI): a response of an animal or an effect on an animal used to assess its welfare. It can be taken directly on the animal or indirectly and includes the use of animal records. 

- Resource-based indicator (RBI): an evaluation of a feature of the environment in which the animal is kept or to which it is exposed.  

- Management-based indicator (MBI): an evaluation of what the animal unit manager or stockperson does, and which management processes or tools are used. 

Iceberg indicator: indicator reflecting major welfare issues in an integrative manner in order to enable an initial overview of the welfare state.