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Contemporary Groups… You can’t have accurate EPDs without them.

Accurate EPDs are an important part of the seedstock business. One critical part of
accurate genetic evaluation is accurate submission of weights and measurements
to the Association. Perhaps the most important component of data submission is
accurate contemporary grouping.
Most reading about this topic may find it boring and dull, but remember, in relation to
your data, the topic is electrifying.

A contemporary group consists of animals that have been exposed to the same external
environment. ASA has four automatic contemporary group splits:
1 – Same sex
2 – Born in the same herd and season (within 90 days)
3 – Managed together and treated alike and
4 – Have the same weigh date
Items 1, 2 and 4 are self explanatory. Defining and discussing item 3 – “managed
together and treated alike” is the objective of this article.
Most contemporary group errors are made when submitting weaning data in the
management code and management group sections of ASA forms. Management code
details are noted first.

Chart 1 lists ASA management code definitions

The second section contains optional management group information. Most often this is
where confusion comes in. If one group of cows are run on irrigated pasture with
exceptional forage resources, and another group of cows are grazing native prairie
grass there will probably be a difference in the weaning weights of the calves.
Therefore, the calves in each group should be reported as being in different
management groups even if they have the same weigh date.

Commonly, breeders think calves can be grouped together even if they were raised in
different pastures. Most think that differences in “prairie grass” pastures on the same
ranch are minimal. Studies have shown that pastures next to each other that visibly look
the same can still cause large discrepancies in weaning weights among the calves in
those different pastures. Inaccurate submission of the data from these two pastures as
the same group causes negative and inaccurate effects on the EPD of both the calf and
the entire pedigree. When submitting data in this case, list two different numbers, such
as 1 or 2, in the management group section.

To most producers larger contemporary groups are perceived to equate to more
accurate EPDs. This is true in reference to higher calculated accuracy values such as
are listed by each trait in the Sire Summary. If larger groups should be split into smaller
groups due to pasture differences, the EPDs you generate by doing this will be more
informative and more accurately relate to the true differences.

To help explain this I’ve borrowed an example from Wade Shafer, Director of
Performance Programs at the American Simmental Association.

Let’s say we have weaning weights on 15 calves apiece by three sires. Let’s also say
they were raised in three different pastures with five calves from each sire per pasture.
If we ignore the rules and group all 45 calves together, it is true that the calves’ EPDs
will have a slightly higher calculated accuracy than if we went by the book and sorted
them into 3 contemporary groups. On the other hand, grouping all the calves together
will actually lower their factual accuracy compared to placing the calves in 3 groups.

The impact on sire accuracy may be surprising at first glance, but it does make intuitive
sense; we would certainly put more faith in a sire tested across multiple management
scenarios and physical environments than a single-contemporary group proof. In this
case properly grouping your calves supplies EPDs as close to an animal’s true genetic
value as possible.

In summary, before filling out that next set of performance forms take a few minutes and
think about accurate contemporary groups.

Common Pitfalls when turning in performance information
Sherry Doubet
August 29, 2013

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One Comment

  1. Posted September 8, 2015 at 9:28 pm | Permalink

    Awesome post.

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