Contemporary Groups

One of the most important aspects of an accurate genetic evaluation is proper contemporary grouping. Environment and management have a large effect on calf performance. When animals are exposed to variable environments or management practices (feed, pasture, shelter, vaccination, etc.), it is impossible to determine if their differences in performance are due to genetics or environment. Selecting the highest performing animals in this situation is likely to result in selecting animals that had an advantageous environment. Because the environment is not inherited, genetic progress is drastically decreased. When every calf is treated as uniformly as possible, the differences between them are more likely to be due to their genetics. In other words, the higher-performing animals are more likely to be the genetically superior animals; selecting the genetically superior animal’s results in greater genetic progress. The creation of contemporary groups is the mechanism that allows us to account for management and environmental variation between animals. A contemporary group is a set of same-sex calves that were born within a relatively short window of time and have been managed the same since birth. Each calf in the group has received the same opportunity to express its genetic merit for traits of interest.

If a subset of calves from a group receives different treatment, then those calves should be recoded as a different contemporary group. An example might be a small group of bulls from the larger group sent to a bull test, or perhaps being pulled out to fit for a show. Those bulls should have their data coded with a different contemporary group than the larger group from which they came. Another example might be if a group of calves is large enough that they can’t be weaned/weighed on the same day, they may be broken into separate contemporary groups and weighed on different days. Once animals are separated into a different group, they can never be recombined with the original group.