DNA sexing has become the preferred
method for identifying the sex of monomorphic birds
(male and females having no external differences). DNA
sexing can be performed with blood and feather samples.
Blood from birds is an excellent source of DNA and for
many years a blood sample was the only means used to
collect a DNA sample. In many cases however, avian enthusiasts
have found that collecting a blood sample is often inconvenient,
and sometimes even impossible. With recent advances
in DNA technology, we can now extract the necessary
DNA to be able to determine sex from just a few plucked
feathers. Both blood and feathers are equally reliable
and provide the same level of testing accuracy. Whether
from blood or feathers, DNA is DNA no matter where it's
extracted from.
Biotechnological advances are affecting
the avian community in many ways. Genetic testing to
determine sex, disease identification, and DNA profiling
are some examples of how biotechnology is used by Avian
enthusiasts all around the world. These techniques are
also continually being improved and expanded. A decade
ago DNA sexing procedures required a large sample of
blood and several weeks to perform. Now samples can
be as small as a single feather or drop of blood, and
assays can be completed in as little as 24 hours without
affecting the reliability of the test. The following
is a brief explanation of DNA sex determination from
feathers.
Why do we Use DNA from feathers
?
DNA sexing from feathers was established
as an alternative method of sample collection. Customers
from around the world wanted a simpler way to collect
samples for DNA sex determination of birds ranging from
ostriches to hummingbirds, penguins to macaws. Avian
Biotech began working on a method in 1994 that allowed
customers to pluck a few small feathers from their bird's
chest or wing for analysis. This procedure helped to
reduce stress, eliminate unnecessary bleeding, and minimize
the chance of infection without compromising the accuracy
and reliability of the results.
What is feather sexing?
Feather sexing could - and should - actually
be referred to as tissue sexing. The reason small freshly-plucked
feathers are used is because it is a very effective
way of collecting the proper amount of tissue cells
needed to perform the analysis. Cells are collected
from the calimus, the portion of the shaft imbedded
underneath the skin. Each tissue cell contains a nucleus
from which a small amount of Genomic DNA can be extracted.
This DNA contains the entire blueprint of the bird,
including its sex. Generally, the proper amount of cells
needed to successfully analyze a sample can be collected
from as little as 3-5 freshly plucked chest or breast
feathers. This may vary depending on the species of
bird and size of the feathers.
What is the difference between
Blood and Feather sexing?
Feather sexing and blood sexing are in
most ways identical. Both procedures
require small amounts of template DNA (DNA isolated
from each sample). Both use an assay procedure known
as PCR. Both, in many cases, require the use of enzymes
to break down the final PCR product before it is run
through an electroforitic gel. Finally, both are analyzed
using photographs and computer scans, and the final
results are identical.
Experience and know-how are vital when
performing any of these assays, as well as when determining
the final outcome. For example, an identical PCR assay
can be performed by several different individuals or
labs with varying levels of success. Some would then
say that the assay is not reliable, while others might
argue that it's not the assay that should be in question,
but rather the individuals doing the testing.
Is feather sexing as accurate
as blood sexing?
YES, using our protocols we have not been
able to detect any difference in the accuracy rates
of blood and feather sexing. The accuracy rate of surgical
sexing varies greatly depending upon the skill of the
individual performing the procedure. When surgical sexing
is performed by an experienced veterinarian the accuracy
rate can be similar to that of blood or feather sexing
done at Avian Biotech.
Are all lab results comparable?
One aspect that must be considered when
comparing results from different labs is that any assay,
test or procedure is only as reliable as the person
or lab performing that procedure. For example, there
are many professional golfers, but not all golfers perform
at the same consistent level that Tiger Woods has for
the last two years. The same can be said for veterinarians
performing surgical sexing, technicians testing blood
or tissue samples, even the performance of labs as a
whole.
When comparing the accuracy and reliability
of different labs it is important to realize that even
though their services may be similar, you may not be
comparing apples to apples. Be sure to ask questions
and learn as much as possible about the individual procedures
and the persons performing those procedures. Some questions
you may want to consider asking are: What methods of
analysis are being used? What type of quality control
system has been implemented? How long have the individuals
been specifically involved with this kind of work? How
much experience do the employees have?
What are the limits?
Like everything else in this world, every
assay has its limits. Our feather sexing procedures
are designed to be used on small freshly-plucked chest
or breast feathers, and not molted feathers, tail feathers
or wing feathers. There are several reasons why plucked
feathers are required for sex identification. The first
is that the amount of quality Genomic DNA required can
only be isolated from freshly-plucked feathers. Molted
feathers do not contain adequate amounts of DNA to run
our standard protocol; thus they generally give us no
result. In order to attempt to obtain a result using
molted feathers, we have to increase the sensitivity
level of the assay using Nested Primer PCR. The increase
in sensitivity could influence the final result by allowing
the assay to become more susceptible to contamination,
which decreases the overall accuracy of the assay.
Another drawback of using feathers instead
of blood is that, at this point in time, DNA sexing
and PBFD testing are the only assays we can run from
a feather sample. DNA fingerprinting and most disease
testing cannot be performed using feathers.
Can Feather Sexing Harm My Bird?
We believe that if the feathers are plucked
correctly from the chest or breast area of the bird,
the bird suffers little from this procedure. Chances
of infection or contamination are almost nonexistent
when done as directed. One person can safely collect
each sample on their own.
Conclusion:
Today there are many different ways to
determine the sex of your birds. It is important to
learn as much as you can and make your own decisions
based on the information you have gathered. When choosing
surgical sexing contact an experienced avian veterinarian
and make sure you understand the risks and limitations
of surgical sexing. When choosing DNA sexing lab ask
questions about their methodologies and lab practices.
Also make sure that you follow the sample collection
instructions carefully. Accurate testing results from
any lab begin with the sample collection.
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