Page 7 - MWC 8-6-20s

The Midwest Cattleman · August 6, 2020 · P7

Strategic and Scientific Bull Selection

By Jaclyn Krymowski

Sire selection, live or in a
frozen straw, is one of the most
important reproductive deci-
sions you will make regarding
your herd. Depending on what
sector of the industry you rep-
resent, this decision can di-
rectly economically impact not
only your cow herd, but your
replacement heifers, animals
on a retained ownership, and
even feedlot or rail perfor-
mance if you feed out yourself.
Knowing your herd and
market are certainly corner-
stones in making this deci-
sion, but there are also other
outside scientific figures that
may be of equal importance.
Research, data and statistics
can bring some new perspec-
tives to your breeding pro-
gram you may not have other-
wise obtained just looking at
your own population. Flying H Genetics
Significance of Genetic Change
Every new sire you bring tion of paired genes on each
into your herd, on the hoof or locus, and epistatic are the
in a tank, brings in some per- interaction of genes across
manent genetic change. Oper- the loci. The sum of the two
ations who retain their own are what creates the heterosis
heifers in closed herds are seen in the resulting progeny.
already somewhat limited in Each parent animal only
their genetic change, relying contributes one gene, so a sin-
heavily on new sires to bring gle parent is unable to trans-
in any new traits they desire. mit dominance effects (or het-
Even if you are practicing cull- erosis) to its offspring within
ing and retain only half your the breed. But multiple breeds
heifers, there will still be some are able to have a significant
“average” quality animals in effect, one that is visible in
the population. To bring those the resulting phenotype of the
up and increase the popula- progeny. This is why heterosis
tion average, you need a sig- is the superiority of a cross-
nificantly higher quality sire. bred progeny compared to
Heterosis is one way to accom- straightbred parentage.
plish this in the commercial Regardless of straight or
herd. crossbreeding, the bloodline
Genetic change is accelerat- of the sire in question will be
ed in crossbreeding programs around for a while. Sires used
with heterosis. These are due in the last three generations
to additive and non-additive in a cow herd keeping replace-
genetic effects. Additive effects ment animals will contribute
are the portion of total genetic 87.5% of the genes in a calf
value that can be transmitted crop, so it pays to be picky.
from parents to offspring; they A Look at the Numbers
are heritable. Non-additive ef- EPDs do some of the work
fects are the dominance and for you in giving the heritabil-
epistatic effects, which have ity of specific traits and what
to do with the interaction of changes you can expect to see,
genes on the loci, or points on while of course accounting for
a gene. genetic variation. The more
Dominance is the interac-
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