Cross
CLAY CENTER, Nebr. - Small
beef cattle herds, for which
complex mating systems are
impractical, generally do not
share crossbreeding advantages.
But they will if a new breeding
system is successful.
The new system is under study
here at the Roman L. Hruska U.S.
Meat Animal Research Center, in
cooperation with the University of
Nebraska, Lincoln.
Under a conventional three
breed rotational system of
crossbreeding, four cows can
produce as much weight of calf at
weaning as five straight-bred cows
of the same breeds.
This advantage can be mam
tamed by continued, systematic
crossbreeding. And crossbred
cows have another advantage
longer productive hves.-
Rotation crossing is difficult and
frequently inefficient when there
are fewer than 80 or 90 cows m the
breeding herd. Science and
Education Administration
geneticist Keith E. Gregory points
out. And 80 percent of the beef
herds in the Umted States contain
50 or fewer cows Many of these
small-herd owners are part-time
farmers
Contributing Breeds
The installation of our mats
in your free stall or stanchion
barn doesn’t just save you time,
which is money, it helps your
herd give more milk, which
means added profit! And more!
Just look at the following:
Hours
Kraiburg Mat
average 4 mats
Lying
Standing
/
INSULATION
WKk
breeding ideal for small beef herd
Gregory and associates are
forming genetic “pools” by
crossmg breeds that, provide a
balance of traits closest to the
performance characteristics most
desired for specific production
situations. Then composite
“breeds” are formed by selective
intermating within the resulting
populations, while maintaining a
low rate of inbreeding.
The geneticist visualizes
general-purpose composites
adapted to various climatic and
feed-resource situations, as well as
composites excelling in maternal
or paternal charactistics.
A small-herd owner would select
a general-purpose composite
adapted to his production
resources. He would manage it like
straight-breds, using bulls from
the same composite.
Cattle producers with more
resources might mate represen
tatives of maternal and paternal
composites to produce market
animals.
The production advantage of
crossbreds results from high levels
of heterosis, or hybrid vigor, when
genetically different animals are
mated. Plant breeders similarly
Ir 7
Genetic
Pool
%
r5O
Solid Rubber
average 4 mats
Lying
Standing
TEXTURED SURFACE
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Composite
Elasticcomfort surface. “Sure-grip” textured surface.
Our advanced rubber chemistry Specially developed tread sur
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oped a surface and a rubber tion against udder injuries,
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pleasant lying surface and re- Excellent heat loss resistance,
suits in noticeably increased Keeps cows’ body heat from dis
milk yield. Testing has shown sipating. Thermal insulation
that increased milk yield results action rejects cold and dampness
from increased comfort in lying from concrete underflooring
and standing time. Details and minimizes mastitis,
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Resists barnyard acids, trapping b UD t 0 $7 000 qq per 100 covvs
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Ryder supply
take advantage of heterosis in crop
production.
Heterosis effects can increase
calf weaning weight per cow by at
least 20 percent, Gregory and SEA
geneticist Larry V. Cundiff found.
That increase is from three
breed rotational crossing, as
compared with straightbreds. The
increase, expressed as weight calf
weaned per cow exposed to
breeding, mcludes cows exposed to
breeding, mcludes cows not suc
cessfully bred and those that
conceived but did not produce a
calf.
The level of heterosis that can be
maintained in composites will be
determined m the current Germ
Plasm Utilization Program.
Under rotational crossing,
heterosis results primarily from
the dominant effects of genes. Loss
of first-generation heterosis under
this breeding system is ap
proximately proportional to loss of
heterozygosity.
“Heterozygosity” is a genetic
term that can best be defined by
example. Genes are the units of
inheritance and are present in
pairs. One member of each pair
comes from the sire and the other
from the dam. When genes of a
pair differ (Aa) they are
heterozygous when they are
alike (aa) they are homozygous.
“Heterozygosity is maximized
when the sire and dam are from
different breeds. Level of heterosis
or hybrid vigor is hightly
associated with the degree of
“heterozygosity.”
In 1922, Sewell Wright, eminent
USDA scientist known as the
“father of modern animal
breeding,” showed that retention
of heterozygosity beyond’the first
generation in crossbreds depends
upon the number of inbred lines m
the initial cross.
Gregory has used Wright’s
formula to estimate the
heterozygosity retention, and he
and colleagues are determining
the extent to which loss of
heterozygosity in composites.
When four breeds contribute'
equally to a composite, Gregory
says about 75 percent of initial
heterozygosity should be retained
in the third generation. Retention
should be about 78 percent m a
five-breed composite in which
three breeds each contribute one
fourth to the genetic base and two
breeds contribute one-eighth each.
Heterosis retention in com
posites should be similar if losses
of heterozygosity and heterosis are
proportionate.
Gregory estimates a possible
increase in calf weaning weight
per cow of 17 to 18 percent over
straightbreds in the four- and five-
P.O. Box 219. R.R.B. Chombenburg, Pa. 17201
Phone: 717-263-9111
Lancaster Farming, Saturday, April 11,1981-4)21'
breed composites. This increase is
intermediate between that in two
and three-breed rotation
crossbreeding systems.
Gregory sees potential ad
vantages of composites over
crossbreeding systems beyond
those directly related to heterosis.
These mclude:
increased genetic variation in
a population based on four or five
breeds should result in greater
opportunity for improvement by
selection;
breeds crossed to form
composites need not be com
parable in birth weight, size, and
milk production. This restriction is
necessary in''rotation crossing,
where genetic composition based
on breed differences fluctuates
widely from generation to
generation; _
similar breeds need not be
No bulging, edge or hair cracks.
Superior compounding and proper
3 / " thickness provide insurance
aging and loss of
10 Year Warranty Program.
Because Kraiburg products are
carefully manufactured and have
been thoroughly tested, we back
every cow mat sold with a Ten
Year Warranty.
|| * \ Available in 10 sizes
[p&r Happy moomcfel
Kraiburg Corporation
10111 Colesvilteßd
Suite 113
Silver Spring, Maryland 20901
(301)593-6565
Tests at leading Animal-Science University
Show - Krai burg Superior to ail tested rubber
and carpet mats. '
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