do it? What to do? How do we do it?
do we Test?
The ADCA requires that the DNA Genotype of all
bulls used for breeding be on file in its Registry
Office before calves sired by those bulls can
be registered. This is true for AI bulls as
well. (While any AI bull whose blood type was
on file in the Registry Office prior to January
1, 2003, is exempt from the DNA Genotyping requirement,
the person who sells semen from that bull is
encouraged to request DNA Genotyping for the
sake of future reference or parentage questions.)
A&M – Dr. Gus Cothran’s Lab
– is the lab of choice for genotyping.
That is where the database for genotyped animals
is housed. If you test at a different lab, you
must make sure that their process is compatible
with that at Texas A&M in order to transfer
the results to the
database. The genotype results must be sent
directly from the testing lab to the A&M
lab – and there is generally a small fee
for that process at A&M.
is a means of ensuring the purity of the Dexter
Cattle Breed. If there is a parentage question
on a calf, the genotype of the bull will already
be on record and can be used to determine the
sire of a calf. It is not usually difficult
to determine the dam. Many people are
beginning to genotype all their animals. This
will insure that the calf is both Sire and Dam
Qualified. At this point, it is not mandatory
to genotype the dam.
Dexter Cattle can carry a genetic mutation
called Chondrodysplasia. This mutation causes
defective bone growth which results in short
legged, heavy bodied animals. Although this
short legged animal is very appealing with its
small stature, the gene can be lethal. If two
carrier animals mate, the statistics indicate
that one in four calves would be a “bulldog”
calf – grossly deformed and born dead.
Statistically, one in four would be a noncarrier,
and two in four would be carriers.
order to be better informed so that a breeder
can establish successful breeding practices,
it is recommended that animals – especially
the shorter legged animals – be tested
for chondrodysplasia. A well-informed breeder
can then make appropriate choices in sire and
dam in order to avoid calf loss due to this
particular gene. If only one of the two is a
carrier, then the bulldog calf will not occur.
There will be a fifty-fifty chance of producing
carrier calves if one or the other parent is
a carrier. If neither is a carrier, then the
problem is eliminated entirely.
(Pulmonary Hypoplasia with Anasarca):
Pulmonary Hypoplasia indicates incomplete formation
of the lungs. Anasarca indicates an accumulation
of fluids in tissues and body cavities. PHA-affected
calves are either aborted or stillborn. Because
of the anasarca, the PHA
calf may be tremendously swollen which would
make delivery exceedingly difficult and potentially
life threatening for the cow. The PHA affected
calf occurs when the PHA gene is inherited from
both the sire and the dam. If only one of the
parents carry the gene, the calf will
appear normal, but can carry the PHA gene.
statistics are similar to the chondrodysplasia
carriers. When both parents are PHA carriers,
there is a 1 in 4 chance of a PHA (dead) calf;
a 1 in 4 chance of a non PHA carrier; and a
2 in 4 chance of producing PHA carrier calves.
When a PHA non-carrier is bred to a PHA carrier,
the chances are 50% of producing a PHA carrier
and 50% of producing a PHA non-carrier. It
is possible for a chondrodysplasia non-carrier
to carry PHA. It is possible for a chondrodysplasia
carrier to also carry PHA. The two genes do
not appear to be related.
give the breeder the knowledge of his animals’
genetic status so that he/she can make appropriate
decisions on breeding practices. By breeding
non-carriers to carriers, you can avoid the
dead calf and potential damage to the cow. By
gradually eliminating PHA carriers from your
herds, you can build a herd that doesn’t
carry this lethal gene. Unlike the chondrodysplasia
carrier, PHA carriers cannot be identified visually.
PHA carriers may be either longer or shorted
Testing for Red or Dun: If a dun calf
is born of parents that are not dun, or only
one is dun, then the calf must be color tested
for dun in order to be registered as dun. The
same is true of a red calf born of parents that
are not both red, or only one parent is red.
The calf must be color tested for red in order
to be registered as red.
Milk Testing: Of the protein found
in cow’s milk, about 1/3 of it is made
up of the protein called Beta Casein. There
are many different forms of this protein, and
the one we are looking at is one of the most
common – called the A2 variant. It is
believed to be the most ancestral form of the
protein. That just means that the other forms
are derived from the A2 variant. We are interested
in the A2 variant because population based studies
of people consuming milk suggest that having
milk that contains the A2 variant of Beta Casein
may be linked to lower rates of heart disease
and type 1 (juvenile) diabetes. It may also
be linked to lower rates of other diseases.
We don’t yet know why this might be true,
or what levels are best. Studies are ongoing
on this topic. (Thanks to Eleanor Conant, Postdoctoral
Research Associate, Dr. Gus Cothran’s
Lab, Texas A&M University.) The test that
we will do is similar to the test we do for
chondrodysplasia, so we can tell if a cow or
bull has 0, 1, or 2 copies of the A2 variant
gene (which will then produce the protein).
So, if a bull has 2 copies, then his offspring
should have at least 1 copy of the A2 variant.
this point, it is really important to know that,
if both parents have been tested as non-carriers
of chondrodysplasia or PHA, it is unnecessary
to test the offspring. They will be “Obligates”
as non-carriers. If you don’t own the
parents, you can go to the online pedigree on
the ADCA website (www.dextercattle.org) and
check the status of the sire and dam. If you
look at their individual pedigrees, it should
indicate if non-carrier status has been obtained
To DNA test your animals for any of the above
tests, you should acquire the appropriate paperwork
– downloadable from the ADCA website.
If you do not have computer access, you may
request that the forms be sent to you by the
ADCA liaison. (Currently the liaison is Pam
Malcuit, 936-394-2606) There are also copies
of all the A&M forms in this handbook. Please
keep them to make master copies so you may copy
and print them whenever needed. They are included
in this handbook for your convenience. Go to
the ADCA website: www.dextercattle.org, and
click on DNA testing. You will find different
tests listed. If you click on the blue lettered
text titles, the necessary forms and information
will pop up for you to download or print.
Texas A&M is the lab of choice for chondrodysplasia
testing, DNA genotyping, Color factor (red and/or
dun) and A-2 milk testing. This lab has not
yet received licensing for doing the PHA testing.
Those labs are Pfizer, Igenity, and AgriGenomics
– also listed online on the DNA testing
tab at the ADCA website.
TO DO IT:
Once you download the forms, please fill them
out carefully and neatly. Make sure you include
all information requested. If the animal is
not yet registered (pending testing) simply
put “pending” under the registration
number. You MUST have a permanent ID for the
either specific brand or tattoo that is unique
to that animal. No two animals should have the
same tattoo or brand number or there is no way
to differentiate them if there is ever a question
regarding paternity, etc. This unique tattoo
number will be listed on the database along
the animal’s registered name (or the exact
name under which it WILL be registered if registration
is currently pending awaiting test results)
and the test results.
it is time to acquire the hair samples used
for the DNA testing. DNA material is contained
in the root bulbs (follicles) of the hairs.
Make sure to PULL out the hairs in order to
include the follicles. Do NOT cut the hair off
of the animal or you won’t have the follicle
needed for testing.
TESTS BEING DONE AT TEXAS A&M: