Simmentaler Joernaal 2013.indb

Simmentaler - Feed the World
Wetenskaplik | Scientific
96
Collecting ‘Effective’ Performance
data for EBV’s
Thys Meyer
(this document was extracted from a combination of BREEDPLAN publications)
“Maximising the effectiveness by which BREEDPLAN can analyse the performance of
animals should be a key priority when recording performance data”.
A key priority when recording performance information
should be to ensure that any performance that is
collected can be used “effectively” by the EBV analysis
performed by BREEDPLAN.
EBV analyses are done for cattle in contemporary
groups to take out the influence of as many of the nongenetic
effects as possible (e.g. differences in feeding,
years, seasons). The underlying principle is that only
the performance for animals that have had an equal
opportunity to perform are directly compared together
within each contemporary group.
The basic mechanism to the calculation of EBV’s is to
directly compare the performance of an animal to the
performance of other “similar” animals within the same
contemporary group.
“Genetic linkage” is then used to compare the animals in
different contemporary groups both within the individual
herd and across the entire breed.
If the contemporary groups are not correctly formed,
the EBVs calculated will be less accurate and possibly
misleading. History has shown that most of the problems
that breeders encounter in “believing” their EBVs can be
traced back to incorrect contemporary grouping – either
calves being fragmented into isolated groups of only one
or few animals (and thereby virtually eliminating those
calves from any comparison with their peers) or by not
differentiating between calves that have had different
levels of management or feeding.
What is an effective Contemporary Group?
The effectiveness of an individual animal’s performance
record is determined by the number of animal
represented within the same contemporary group.
Calves will be analysed in the same contemporary
group if they:
1. were bred in the same herd,
2. are of the same sex,
3. are of the same birth number (i.e. twins not compared
with single calves),
4. are of the same birth status (i.e. ET calves not
compared with AI/natural calves),
5. were born in the same calving year,
6. were born within 45 days (for birth and 200 day weight)
or 60 days (for 400 and 600 day weight) of each other,
7. have been weighed on the same day (& have the
same weighing history),
8. have been run under the same conditions.
When there are no other similar animals to which the
animal’s performance can be compared (ie. a single
animal contemporary group), the performance is not
effective and does not contribute to the animal’s EBVs.
When the animal is in a contemporary group of 2,
the performance is 50% effective, in a contemporary
group of 3, 67% effective, in a contemporary group
of 4, 75% effective and in a contemporary group of 5,
80% effective. After 5 to 10 animals are represented in
a contemporary group, the increase in effectiveness
diminishes quite rapidly with increasing group size,
although the objective of Stud Breeders should be to
maximise the contemporary group size. This increase in
the effectiveness by which BREEDPLAN can analyse an
animal’s performance record is illustrated in Figure 1.