Excerpts courtesy of Jos Mottershead of
What are the advantages and disadvantages
of frozen semen?
A: Frozen semen advantages
There is no requirement to schedule shipments
of semen to fit the mares ovulation time.
The stallion does not have to be taken
out of competition to breed, or have his
competitive attitude possibly upset by
having to be bred.
The market for semen is global, as there
is no limitation on duration of delivery
There is an "insurance factor",
should your stallion become ill or die,
and be unable to fulfil his breeding commitments.
Not all stallions have semen that will
Conception rates for artificial insemination
with frozen equine semen are typically
a little lower than those seen with fresh
or cooled semen ("transported semen"
or "shipped semen").
To freeze semen is not initially as cheap
as to prepare cooled semen (although in
the long run it can be cheaper).
The average farm will not wish to set
up their own laboratory, or have the technical
know how to freeze semen.
What is involved in freezing semen?
A: Once the semen is
collected from the stallion, which is
the same process as collecting for cooled
transported semen or on farm AI (artificial
insemination), it is evaluated to establish
sperm concentration and motility levels.
The semen is then mixed with a centrifugation
extender, and the majority of the seminal
plasma is removed by centrifugation. The
resulting sperm pellet is resuspended
in a freezing extender which contains
a nutrient medium and a cryopreservant.
This mixture of sperm and extender is
then loaded into straws. The straws are
then lowered in temperature by being exposed
to liquid nitrogen vapour for a timed
period. After the completion of that timed
period, they are plunged into the liquid
nitrogen, from which they can subsequently
removed, and stored in a liquid nitrogen
storage container. Of course, this is
just a simplified outline of the procedure,
and there are several different techniques
If the freezing procedure is as simple
as outlined above, why isn't it more common?
A: It's not quite as
simple as the outline! There are several
variables, not the least of which is the
Not all stallions semen can be successfully
frozen. Or to be more accurate, can be
successfully thawed! It's estimated that
between one-third and one-quarter of stallions
have semen that when frozen, thawed and
inseminated into a suitably receptive
mare, will not result in pregnancy. Research
is producing new methods all the time,
and it is hoped that this figure will
reduce in time.
Attention must be closely paid to all
the procedures involved in the freezing
process. Stallion sperm are extremely
sensitive, and will die (it sometimes
appears) at the drop of a hat! Any part
of the process that is not carried out
properly will result in a reduced percentage
of sperm capable of impregnating a mare.
As there are many more steps in the semen
freezing process than there are for preparing
cooled semen (transported semen or shipped
semen), the potential for disaster is
I looked at having my stallion's semen
frozen, but the cost was prohibitive.
Is there anything I can do to reduce the
A: Not really, but
costs have dropped significantly in the
last five years, so it may well be worth
checking the price again. Prices are now
such that it should be practical for anyone
who has a stallion that is breeding a
reasonable number of mares at an average
stud fee to utilize freezing services,
providing their stallion is a "freezer".
How do I know if my stallion is a "freezer".
A: Unless his sperm
have been frozen, there is really no reliable
method to tell whether they will survive
the process. Even then, because they have
survived the freezing process does not
mean they will be able to get a mare pregnant.
Some businesses freezing semen offer a
special rate for a "test freeze".
If my stallion has had his semen frozen,
and we have used it to successfully to
breed mares, how long will the frozen
semen last that we haven't used?
A: As long as the semen
is not thawed, and is maintained in a
liquid nitrogen storage tank, the working
life is believed to be nearly unlimited.
(10,000 years has been suggested!) Realistically,
pregnancies have resulted from using semen
that has been stored for ten years or
Is thawing the semen before breeding by
artificial insemination complicated?
A: No! But care and
attention must be paid to the process.
(More information can be found on thawing
equine semen here).