Alternative genetic bases for sire summaries and cow indexes

The need is discussed for understanding the interpretation of Predicted Differences in relation to the 1974 genetic base. Merits of moving, fixed, and stepwise genetic bases are discussed in relation to genetic progress in the United States dairy industry. A moving genetic base has little merit, because too many animals are evaluated and published in each sire summary. Either a fixed or stepwise base could be used effectively if dairymen and industry personnel were educated on the relation of current genetic evaluations to the genetic base and the need to continue genetic improvement in individual breeds.