After the first appraisal of general appearance, most of us look for thickness or muscling. Fortunately observing differences in muscling is fairly easy. Almost everybody can determine if one bull has more muscle in its hindquarter or over its loin and rib than another with a little practice.

Muscling equates to weight and weight at a given age (e.g. weaning weight) is an example of growth rate. As young bulls mature, they will show more muscle.

Looking at bulls will help you determine if one has more muscling than another, but not how much, that is where expected progeny differences or EPDs can be used. The various records (breeding, calving, weaning, etc.) collected on purebred animals or their progeny are compared and these EPDs are calculated. They are the best estimate of how this bull’s progeny will perform compared to other bulls. Actually, EPDs are calculated on both bulls and cows, but we’re talking about bulls here.

The data for the EPD calculation is taken from the bull’s own records and any relatives (parents, grandparents, sibs, and offspring) with the same records. The more records collected, the more accurate the EPD. Young bulls often have excellent EPD but because the low number of records used in the determination, the accuracy is lower.

Once the bull has progeny and their records are reported, the accuracy will increase (but the EPD can either increase or decrease depending on the level of performance of the progeny). The EPD are updated several times a year as new data arrives from breeders. Some compute them weekly. Until recently, EPDs were the best method for determining the genetic value of cattle. Now most breed associations use genomic enhanced EPD (GE-EPD).

The GE-EPD improves the accuracy of the EPD of young bulls and females, almost doubling it in some cases, by taking into account similarities in the genes of relatives. The GE-EPD is now used by most purebred breeds. Also, many breeds have assisted bull buyers by incorporating several economically important EPD into production indexes so that bull buyers can find either maternal or terminal type bulls more easily. Bull buying with EPD or the production index will help take a lot of the guesswork out of your selection decisions.