Performance Line
quite a range! You’ll notice
that reproductive traits have
the lowest heritability. In
contrast, you will see that
traits like stature are highly
heritable, with over 80% of
the variation in performance
being explained by variation
that exists in breeding values.
Table 1 - Heritability estimates for
common traits in beef cattle.
Trait
Average
Estimate
Reproduction
Calving Interval 0.08
Fertility 0.10
Growth
Birth Weight 0.45
Gain, birth to
weaning 0.30
Weaning weight 0.24
Feedlot gain 0.34
Pasture gain 0.30
Height
Hip height at
weaning, creep fed
Hip height at
weaning, non-creep
fed
0.82
0.95
Carcass
Grade 0.50
Ribeye area per cwt 0.70
Retail product,
pounds 0.60
Table available at:
https://extension2.missouri.edu/g2910
Taking a look at Figures 1 and
2, we can see that variation in
performance that exists in lowly
heritable traits is explained more
by variation in environments in
which animals are raised and
the way genes combine, and
very little variation is explained
by genetics that can be passed
on from the sire or dam to their
offspring. On the other hand,
the genetics passed on from
parents to offspring for highly
heritable height traits explain
50% or more of the variation
that exists in performance
for those traits. This means
that it will be much easier to
change animal performance
for the highly heritable traits
through selection decisions
(choosing individual bulls and
cows with desirable EPDs for
those traits). For lowly heritable
traits, animal performance
depends much more on the
environment (everything non-
genetic from conception to
death) and the way the genes
combine (avoiding inbreeding).
It becomes apparent then,
that indeed, breeding cattle
is as much art as it is science.
Certainly, you have powerful
tools in the form of GE-EPDs
(our best estimate of 1/2 BV),
and genetic progress can be
made for all of the traits. This
genetic progress will translate
to rapid changes in phenotype
for some traits, while others will
take more patience. However,
you must also be aware that
the way you chose to mate
animals impacts the way
genes combine, contributing
to inbreeding or heterosis. The
environment ultimately plays
a key role in the way animals
perform and fantastic genetics
can be easily covered up by
unfortunate environmental
circumstances. I
Figure 1 - Cmponent weights for lowly
heritable traits
E = Environment; BV = Breeding Value;
GCV = Gene Combination Value
Figure 2 - Cmponent weights for highly
heritable traits
E = Environment; BV = Breeding Value;
GCV = Gene Combination Value
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