What?
Contemporary groups refer to groups of animals that have been exposed to very similar environmental factors throughout their lives, thereby accounting for all environmental factors when comparing the performance of the animals for a specific trait. Contemporary groups enable animals to be compared on a genetic level as all the environmental bias on a specific trait is accounted for. These groups enable the calculation of individual estimated breeding values (EBVs) for each animal in the group for a specific trait. EBVs enable animals between and within contemporary groups to be compared to one another in the same genetic evaluation run however, animals should never be compared across different genetic evaluation runs.
The primary environmental factors that form the basis of contemporary group creation are defined by the simple acronym; HYSS or Herd/Year/Season/Sex, among others. Animals that are born within the same herd, then the same year, then the same season and of the same sex can be grouped together. For example, heifers, steers and bulls fall into 3 different contemporary groups. It is also important to differentiate between calves that have had specific management or feeding programs that were different to the rest of the group. For example, bottle-fed calves cannot be grouped differently together with calves that drank and were weaned from their mothers.
Age of the dam, single/twins, and birth status (ET or Natural/AI) are other influential factors that dictate further development of contemporary groups. However, in some instances, adjustment equations may be used to correct for these factors to allow for larger contemporary groups.
Emphasis must be placed on larger contemporary groups where possible! The larger the group of animals that have experienced the same environmental conditions, the more contemporaries there are for an animal’s performance to be compared against for a specific trait. Contemporary groups are effective if they have been 1) formed correctly, 2) consist of many animals and 3) contain genetic linkage. To obtain valuable information from contemporary groups, one should aim to create fewer of them but have many animals in those that are created. Hence, the emphasis on three primary environmental factors, H/Y/S. Additionally, the valuable information yielded from contemporary groups increases if there are genetic links within and between groups. This is achieved when a contemporary group contains more than one offspring (half-siblings) from a sire and furthermore, if that sire also has progeny in other contemporary groups. This will increase EBV accuracies for the sire as a parent, as well as relatives of the sires.
Why?
Accurately recording trait measurements can tell one a lot about an animal. However, those measurements cannot tell you much about other animals, nor can they accurately compare one animal to another if the environmental effect on that performance is not accurately accounted for. Therefore, to determine the degree to which variation in performance is due to genetic differences and not simply environmental advantage/disadvantage, comparisons need to be made based on performance within a group of animals that are environmentally similar. Contemporary groups level the playing field in terms of the environmental influence on performance by grouping animals that have had a similar environmental experience together and therefore, can be appropriately compared to one another.
When the BREEDPLAN run occurs monthly, genetic evaluations for EBVs are conducted based on contemporary groups. If trait measurements for an animal are measured and sent in at random times or in unstructured groups, then the possibility exists for that animal to be put in a contemporary group by itself. Consequently, the information yielded from the subsequent genetic evaluation for that animal may not be very informative as it does not provide much for that animal to be compared against.
How?
One should start thinking about contemporary groupings as soon as a calf is born. Further, BREEDPLAN has outlined slice groups (age parameters) to assist breeders in the development of contemporary groups. These slice/age groups indicate which animals within a particular herd, year and season could be compared with one another. For example, the slice group for calving trait EBVs (birth weight and calving ease) is 45 days; meaning that animals born in the same herd, year, season and within 45 days of one another, may be placed into a contemporary group. The slice groups for all the other BREEDPLAN traits are listed in the LRF Test Plan – which is available on the LRF website.
Defined breeding seasons, which subsequently assist in defined calving seasons, make contemporary group creation much easier than year-round breeding/calving. By implementing two breeding seasons of 60 days each (90 days in Namibia) in the summer and winter, one creates tight calving windows that almost automatically create larger contemporary groups when calves are born. It is more challenging to define the “season” aspect of a contemporary group and work out slice groups if calves are born throughout the year.
In general, BREEDPLAN genetic evaluations are conducted on contemporary groups whereby calves were:
- Bred in the same herd,
- Born in the same calving year,
- Of the same sex,
- Of the same birth number (singles are not compared to twins),
- Of the same birth status (natural/AI calves are not compared to ET calves),
- Measured/weighed on the same day,
- Of similar age (age slicing is 45 days for birth weight and 200d weight, and 60 days for 400- and 600d weights),
- Run under the same management conditions and/or feeding program (which may be indicated by the breeder by using a specific management group code).
Figure 1A is a graphic depiction of bulls that vary based on one or more of the above-mentioned factors, before they have been organized into contemporary groups. Figure 1B illustrates how they may fit into respective contemporary groups. The bulls all belong to the same herd, but they vary on several other factors (indicated by a colour in the figure) and thus must be grouped accordingly. The 10 orange bulls were all single calves, conceived by natural mating and subsequently, run under the same management group. However, the five larger bulls were born a year before the smaller five and thus are not of similar age (not born within the respective age slice for the specific trait), nor were they weighed on the same day. As a result, two separate contemporary groups can be seen for the orange bulls in Fig. 1B.
The two blue bulls and two black bulls were two sets of twins born in the same year, same calving season, are of similar age, and were measured on the same day for various traits. However, the two blue bulls were conceived naturally, whilst the two black bulls were by ET, meaning that their birth statuses differ, and their management conditions might also differ. Subsequently, two separate contemporary groups are represented.
The green bull was born in the same year as the five small orange bulls, was also conceived naturally, was measured on the same day and is of similar age to the five small orange bulls (born within 45 days of one another). However, where the five orange bulls were run on the veld, the green bull’s dam received a show-conditioning diet during the gestation period with him and thus, he cannot be placed in the same management group as the five orange calves.
Therefore, one may infer that comparing all the animals in Figure 1A together in one group for a specific trait may not provide an accurate or comprehensive comparison within the group whereas accurately accounting for the environmental factors as in Figure 1B may provide a truer representation of an animal’s genetic potential for a specific trait given the stipulated environmental conditions.
Figure 1A
Figure 1B
Please contact the office should you want more information on contemporary groups and how to indicate management codes when submitting data to the office.