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. In addition, the NAAB guidelines state that the following information should also be included. Number of direct comparisons. This is the number of calvings for each sire that has direct comparison with calvings of contemporary herdmate sires in the same herd, year and season.
Direct comparison is necessary to rank sires accu- rately.
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. This makes it possible to compare a bull with a high estimated transmitting ability based on only a few reported births to a second bull that has a lower estimate, but one that is based on more calving reports.