Technical information - selection

Get the comparison right

by Craig Croker TROPICAl beef technology services

BRAHMAN NEWS MARCH 2007 Issue #154

Recording the date of birth, mothering up calves, weighing, measuring scrotal circumference & ultrasound scanning as all those who undertake it know; takes considerable time & effort. In regards to genetic evaluation you hope that this information is contributing to give a more accurate estimation of the animal’s genetic merit. A common mistake however is that once the physical work is done performance is submitted without due care to comparison groups, otherwise know as contemporary groups.

In the calculation of BREEDPLAN EBVs it is not the actual raw performance (e.g. weight) that is important but rather how the performance compares to the rest of the animals in the contemporary group. Thus the importance of getting these groups right.

Figure 1 shows an example of how a mob of weaners are divided to produce groups of animals that have had the same opportunity to perform & thus can have their performance directly compared against each other. The formation of contemporary groups relies on a number of automatic & breeder defined factors.

Most of the factors affecting contemporary groups are taken into account automatically from the animal’s pedigree information. These include the animal’s age, sex, or wether their AI or a natural calf. There are other factors however that can be influenced by the breeder. These factors are referred to as management groups (indicated by the green arrow in figure1) and include for example differences in nutrition or identified disease.

It is important that you the breeder have a good understanding of the grouping process to ensure as they say “apples are compared with apples”. Difference in management groups should be recorded alongside any performance & submitted to BREEDPLAN to make sure this is the case. Some examples of where animals should be recorded in separate management groups are:

  • Animals that have been sick
  • Animals have been fed for show or sale
  • Grain fed animals versus paddock reared animals
  • Animals with growth promotants
  • Animals from paddocks of different nutritional value
  • A bull has been fighting & has clearly lost weight prior to recording
  • Yearling bulls that have been joined
  • Different stages of pregnancy for heifers (try to weigh prior to joining & certainly before 2 months)
  • Spayed heifers versus non spayed heifers
  • Calves weighed straight from the paddock compared to those that have been in the yard overnight.

In regards to different paddocks; the animals should be grouped separately if there was a significant difference in available nutrition. For example animals that have been grazing on a forage crop should not be compared against those grazing on native pastures. If paddocks are grouped separately then it is ideal to have more then one sire represented in each paddock. This allows the direct comparison between the different sire’s progeny which is of basis of the genetic evaluation. Having more then one sire represented in a calving grouped in a single sire operation is simply achieved by mixing the cows prior to calving.

Another area of consideration is with embryo transfer (ET) calves. ET calves are also grouped for comparison on the breed of their recipient dam. Thus using several different breeds of recipient dam’s can reduce your contemporary group size dramatically. In order for an ET calf’s own performance to be used the breeder must submit information on the recipient to BREEDPLAN i.e. age, breed & ident.

In summary the aim is to maintain good sized contemporary groups throughout recording but not to the expense of including animals that didn’t have the exact same opportunity to perform. Good comparisons produce increased accuracy of figures which inturn enables smarter selection decisions.

For any further information on contemporary groups or maximising your evaluation please feel free to contact TBTS at anytime on 07 4927 6066 or email

Also look out for information in the mail soon on the TBTS workshops to be conducted across QLD “BREEDPLAN & related technologies: The Essentials, 2007 alternatively check out the website for more details.