When combining herds (by exporting one herd in to the same data file as another herd) the event structures of the herds are examined before they are combined. Where event codes in the two herds differ it is necessary to import the event code as well as the animal records.
In the example above the ABO code appears in both the source herd and the target herd so there is no need to import the event code. However, the BULL+ event is used in the source but not the target herd. Hence the BULL+ event will be added to the event definitions in the target data file.