This document provides guidance on usage of biometrics in breeder documents, in particular regarding encoding of biometric reference data, data quality maintenance for biometric reference data, data authenticity maintenance for biometric reference data, and privacy preservation of biometric reference data. This document addresses advantages and disadvantages of biometric modes, in particular regarding verification performance, privacy impact, feasibility of biometric acquisition considering the age of the capture subjects, limits of validity and need for updating biometric reference data. The following aspects are out of scope: format and structure of breeder documents, general security aspects, which are covered in CEN/TS 17489-1 [1].