The Keystone of Your Data
The purpose of a contemporary group is to identify measurable differences in animals raised under the same management and environmental conditions. By minimizing variations in management and environment as much as possible, it is easier to identify differences in weights or other measurements due to genetics. There are other non-genetic differences in weights such as the age of the animal and its dam when the measurement was taken. These differences are accounted for by adjusting the actual weights or measurements to a common base. For example, actual weaning weight is adjusted to a 205-day adjusted weight. An adjusted weight by itself provides no genetic information. Genetic information is only obtained when an adjusted weight is properly compared to adjusted weights of other animals that had the same opportunity to perform, i.e. in the same contemporary group.
Since contemporary groups are an important part of genetic evaluation, having the best information to form contemporary groups is important. Errors are introduced when animals are treated differently or raised in different environments but put in the same contemporary group.
Breeders submit weights and scores on animals and these measurements are adjusted for such things as the animal’s age and the age of its dam. But it’s the contemporary group that adds meaning to those measurements. It answers the question, “Compared to what?”.