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DNA fingerprints lift wool clip quality
doption of genetic fingerprinting in the
Merino industry is set to herald a
dramatic improvement in the quality of the
nation’s woolclip.
The fingerprinting technology, developed
by CSIRO Animal Production, will accelerate
the genetic improvement of the industry by
identifying rams and ewes with desirable traits
and eliminating those with undesirable
characteristics such as black or coloured wool.
Some wool growers are already using the
technology successfully and new developments
have reduced the cost of the procedure,
making it a viable option for more producers.
The fingerprinting technology is based on a
simple blood test carried out to isolate and
characterise the animal’s deoxyribonucleic
acid (DNA) and allows sheep breeders to
identify the likely parents of a lamb.
It is known as fingerprinting technology
because, like fingerprints, DNA does not
change and it is possible to determine the
identity of a person or animal from a tiny
blood sample.
The technology is also based on methods
used to help resolve disputes of human
parentage.
Accurate pedigree information can allow
Merino breeders to achieve better estimates of
their animals’ genetic value and quickly
discard inferior animals from breeding flocks.
Commercial wool producers will have the
opportunity to buy rams that have been bred
selectively for highly desirable qualities such
as fine wool, no black wool and more efficient
fleece growth.
The technology will also help producers
compare the merit of rams bought recently
and those bought in the past as well as
A
• DNA fingerprinting technology
is being used in the Merino
industry to eliminate wool
faults and improve fleece
quality by determining the
pedigrees of sheep with
desirable and undesirable traits.
• Farmers can prepare tests for
DNA analysis by pricking the
sheep’s ear, soaking the
blood onto special filter
paper and sending the
sample to be analysed.
inbrief
• Results are sent to the farmer
within a few weeks to help
select ewes and rams.
• Researchers are developing
genetic markers for traits
such as fleece weight and
fibre diameter.
72
by Jane Rogers,
KONDININ GROUP
Science and Macquarie University aim to have
the kit widely used in the Merino industry
during the next 12 months.
Traditional breeding methods
CSIRO
LIVESTOCK
Breeding
Sheep
Merino breeders across Australia have the
opportunity to adopt new technology which
promises to eliminate undesirable characteristics
from flocks. DNA fingerprinting technology is
allowing breeders to identify the likely parents
of a lamb.
providing a clearer picture of the genetic
trends in their flocks.
Another benefit of DNA fingerprinting is
that it provides commercial wool producers
with detailed information about the value of
sheep before they are bought and this should
allow more flexibility when sourcing animals in
the future.
The ultimate aim of the work is to produce
a genetic fingerprinting kit which will help
speed the selection of breeding animals and
lift the rate of genetic improvement in the
national flock so wool can compete favourably
with alternatives such as cotton.
Project collaborators CSIRO Animal
Production, Victorian Institute of Animal
At present, Merino breeders who want
pedigree information rely on a labour
intensive system of running ewes in single sire
mobs so they can track and record the
parentage lines.
But this method relies on tagging newborn
lambs according to their apparent mothers
and fencing an area into small paddocks to
accommodate different sire groups.
The CSIRO has estimated the cost in
labour, watering and fencing to be as much as
$15 per lamb.
The accuracy of assessing flock pedigrees
using this method also can be reduced by
sheep breaking through fences and, more
commonly, natural cross-fostering of lambs.
In some cases researchers have found crossfostering errors of lambs to be 10% or more.
DNA testing has shown cross-fostering levels
of 10-20%.
Other problems include reduced lambing
percentages if a ram in a single sire paddock
has a low fertility level.
Due to these constraints only a proportion
of Merino studs use some kind of pedigree
information.
Most only identify the sire with very few
collecting a full pedigree.
Researchers hope DNA fingerprinting
technology will provide sheep breeders with a
more precise and economical tool to identify
the parents of lambs.
The benefits of establishing accurate
pedigrees for Merino sheep include:
Quick results from DNA tests
estern Australian Merino breeder John
Dunne is using DNA fingerprinting in his
stud breeding enterprise.
W
During the 1980s the Beacon-based farmer
recorded the full pedigrees of his flock and
progeny-tested several rams each year in order
to make better breeding decisions.
This exercise gave John a clear understanding
of the costs associated with such an intensive
operation in terms of the labour required
to install and maintain fences and watering
points, as well as for the collection and recording
of data.
To ensure that his replacement sires did not
carry the recessive black gene, Mr Dunne
maintained a flock of about 80 black ewes for a
number of years and joined up to 15 at a time to
his best performing rams each year. While a
black or coloured lamb is now a rarity in the stud
flock, they are still causing some embarrassment
for Mr Dunne among some of his clients’ flocks.
After hearing about the CSIRO’s DNA pedigree
technology during 1997, Mr Dunne realised its
enormous potential for identifying carriers of the
black gene.
With the co-operation of the CSIRO, a local
veterinarian and his clients, Mr Dunne has tested
about 75 sheep belonging to his clients, to
specifically identify a number of black lambs and
all their possible sires.
There has been a significant reduction in the
incidence of black lambs in all but one flock, and
further testing this year using the technology is
expected to eradicate all black sheep from their
FARMING AHEAD No. 83 - November 1998
• More precise progeny testing of rams to
improve estimates of their genetic value.
• Tighter control of genetic improvement.
For example, it is possible to eliminate
sires or dams that carry genes for black
wool,
metabolic
disorders
or
conformation faults.
• Being able to plot genetic trends in the
flock over time to obtain an average
genetic value of the flock. Currently
there is little objective knowledge about
the rate of genetic improvement in the
Merino industry.
• Reduced inbreeding because breeders
can monitor the relationships between
rams and the ewes to which they are
mated. Inbreeding can reduce fertility
and wool production.
DNA pedigree technology is also used
widely in the racehorse and greyhound
industries.
Owners currently pay about $80 per head
for a DNA test but the different structure of
the Merino sheep industry makes such costs
prohibitive.
The CSIRO research team is fine-tuning a
simple, inexpensive and accurate test kit ready
for commercial release during late 1999.
DNA testing is particularly suited to the
Merino industry because of its hierarchical
stud structure.
This means the benefits of pedigree testing
on a ram breeder’s flocks will spread
throughout the industry without the need to
test animals on an industry-wide scale.
FIGURE 1 Sheep DNA
The genetic make-up of a lamb is
determined by the fusion of genetic material
from its sire and dam.
The unique combination of genes is
established at fertilisation and provides a
‘blueprint’ for the lamb’s physical appearance.
A gene is a tiny unit of DNA carried on
ribbon-like structures called chromosomes.
Each chromosome contains thousands of
genes attached in single file along its length
(see Figure 1).
Chromosomes are made of two chains of
DNA, arranged together to form a spiralling
structure.
Scientists use a process called polymerase
chain reaction (PCR) to magnify areas of the
DNA so they can isolate sections of genetic
material that vary greatly between individual
animals. These sections may vary in length or
the DNA code may read differently.
The PCR process involves heating and
cooling a sample of DNA, which can be as
small as one molecule, so that a specific
fragment of the DNA can be copied many
times, making it easier to identify and read.
The highly variable DNA sequences are
known as markers and scientists worldwide
Parakeelya 9P681 which, apart from the black spot
on his nose, gave all appearances of being a pure
white ram.
The black ewes were joined with Parakeelya 9P681.
Black ewes by definition must carry two copies of
the recessive black gene.
DNA typing
flocks. Mr Dunne considered the cost of $25 per
DNA sample commercially viable in his situation,
believing there was no other way he could
have achieved such definitive pedigree
information so quickly.
FARMING AHEAD No. 83 - November 1998
While Mr Dunne has been using the technology
to remove unwanted traits. He said the greatest
benefit was likely to be in identifying animals with
desirable characteristics and so increasing the rate
of genetic improvement in the Merino industry.
have identified 500 markers in sheep. The
markers are used to identify a location on a
chromosome that may be associated with a
particular trait (see Figure 2, page 74).
To determine parentage in Merinos,
scientists have sifted through all the markers
available and chosen to use 15 variable length
DNA markers (also known as microsatellites).
These microsatellites consist of different
repeats of the DNA code.
For example one animal may have a code
with three repeats such as ABABAB while
another will have six repeats such as
ABABABABABAB.
The number of times the code is repeated
varies between animals but a parent will pass
its motif to the next generation in exactly the
same form.
By studying enough of the microsatellites on
different chromosomes it is possible to match
a lamb’s DNA pattern to its parents’.
To make the system commercially viable the
CSIRO has chosen 15 markers so they can be
tested simultaneously using one or two tests
for each lamb rather than testing for each
marker individually.
Collection method
In an effort to cut costs the CSIRO has
devised a method where farmers can collect
blood samples for DNA analysis rather than
employing a veterinarian.
The farmer needs to prick the lamb’s ear
and soak the bloodspot onto special
filter paper, taking care to record each
sample accurately.
The samples are sent to the CSIRO
laboratory and the DNA extracted from
the blood sample using a simple and
inexpensive method.
Robotics are used in the laboratory to
handle the samples for optimum accuracy and
to minimise labour costs.
Pictured are Parakeelya 9P681’s progeny from
the black ewes. The two black lambs are proof
that 9P681 is a black ‘carrier’. Because the
‘white’ lambs are known to be progeny of 9P681
out of the black ewes, they too must be black
carriers (heterozygous) and are destined for
slaughter if females and castration if males.
73
LIVESTOCK
Sheep...
LIVESTOCK
Sheep...
The CSIRO is currently holding a trial with
some Merino breeders to test for sire-only and
full pedigree information. The aim of the trial
is to streamline and enhance the system to
ensure sheep breeders find it profitable to use
DNA testing.
Economic analyses carried out by the
CSIRO have shown the cost of the test needs
to be reduced to about $10-$15. At present
each test costs about $25.
FIGURE 2 Comparing DNA markers
Mark Casey
The first step
The market demands wool growers produce
consistent, high quality, clean wool free of black
fibres..
The only labour-intensive stage of the
testing is loading each DNA sample onto a
special gel to enable analysis.
After individual lamb samples are loaded,
automated software is used to read the gel and
the information is transferred to a computer
program which analyses the results and
generates a report to be sent to the farmer.
The system has been developed to minimise
labour costs and maximise efficiency at every
stage, from blood collection, transmission of
samples to the laboratory, genetic marker
analysis to the final report to the farmer.
DNA pedigree testing is the first step in
molecular genetic technology and breeders
who start recording the parentage of their
sheep can take advantage of new genetic
markers as they become available.
The research team is using its parentage
trials to measure important commercial traits
such as fleece weight and fibre diameter, and
subjective measurements such as colour and
style of wool, in the hope that they will identify
more markers for genes that contribute to
variations in wool quality.
As scientists are able to alter an expanding
range of traits, farmers who are pedigreeing
their flocks can immediately screen for the
new markers at a relatively minor cost. It will
then be possible to select sheep that have the
highest chance of transmitting desirable traits
to the next generation. Sheep breeders who
want to take advantage of DNA fingerprinting
Make your
hay and
Lamb 2 has inherited the upper marker band
from its mother (ewe) and the lower band from
its father (ram), indicating that these are the
correct parents. Neither of the bands in Lamb 1
have been inherited from the ewe or ram.
now have access to a new consultancy service
developed by the CSIRO, known as Select
Breeding Services.
For further information contact Select
Breeding Services or Ian Franklin at
CSIRO Animal Production on phone
(02) 9840 2700 or fax (02) 9840 2940.
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74
FARMING AHEAD No. 83 - November 1998