In an effort to provide uniformity of information available on calving ease, the NAAB has established guidelines for publishing calving-ease data. These guidelines indicate that the latest available information should always be published along with an indication of the source and date of the information. Usually the source is the NAAB Dairy Sire Summary For Calving Ease. It is important that this information be provided, however, so a reader will know that the information is reliable. This is the number of calvings for each sire that have direct comparisons with calvings of contemporary herdmate sires in the same herd, year, and season.
Direct comparison is necessary to rank sires accurately.
A bull may have more calvings reported, but the number of direct comparisons indicates how many were actually used in his summary. Probability that the sire's true transmitting ability for calving ease is above breed average. This expresses the probable change in transmitting ability for a particular sire as more calving reports become available. This single value takes into account both the bull's estimated transmitting ability and how accurately his transmitting ability is estimated. It would be comparable to combining a bull's PDT with his repeatability to rate him for production.