The ID numbers printed on them are allocated from the GB Livestock Unique Identification Service (LUIS) to suppliers of approved identifiers/ear tags.
Bydd y sgrinio ar ffurf sampl gwaed sy'n cael ei chymryd o'r anifail/anifeiliaid gan filfeddyg preifat cymeradwy a'i hanfon i labordy cymeradwy i'w phrofi.