STALLION MANAGEMENT
Lesson Ten
USE OF COOLED, SHIPPED STALLION SEMEN
It takes particular expertise and
teamwork to obtain a proper semen specimen from a stallion, so, once it is
collected it is very important the sample is handled in a manner that does not
cause excessive damage to the spermatozoa. (Many common semen handling
techniques have been found to actually damage the semen; we don’t want that to
happen.)
The sperm cells of the horse are among
the most fragile of any species when it comes to survival outside the animal
(in-vitro environments). This is especially true when it comes to drastic
changes in temperature----an obstacle that is difficult to avoid when
collecting semen in the middle of winter. In its natural environment, sperm is
kept at approximately 98 degrees Fahrenheit (37 degree celcius).
That is a temperature much warmer than the atmospheric temperature during much
of the breeding season.
Care must be taken to have all contact
surfaces warmed to near 100 degrees Fahrenheit. Keeping the bottles, pipettes,
syringes, and extender media in an incubator will reduce the possibility of
death due to cold shock, the term used to describe hypothermia in sperm cells.
Overexposure to low temperatures causes the male gamete to develop a
characteristic appearance: the tail bends backward in an arc toward the head.
This causes the live cell to swim in a circular motion. This deviant movement
prevents the cold-shocked sperm from being able to compete with the straight
forward moving sperm in the race to fertilize the egg. Therefore, a
cold-shocked sample decreases the fertilizing capability of an artificial
insemination procedure and makes it more difficult to accurately evaluate the
fertility of a horse.
Ultraviolet light must be avoided.
Place a semen sample in a clear
container in direct sunlight and within minutes the mass slaughter of sperm
cells will begin. To counter this problem, semen should be collected in
containers that have ultraviolet ray filters and then be quickly moved into
work areas devoid of ultraviolet light.
The next two lethal conditions concern
only those reproductive physiologists trying to protect the semen sample for a
long period of time or breeders interested in preserving the semen for breeding
mares in localities distant to the collection point. (AI with
shipped semen).
As the ejaculate waits to be
processed, it becomes its own worst enemy. By-products of cell metabolism
change the acidity of the environment. The waste produced by billions of cells
becomes life threatening to all the cells in the beaker - a concept we are
becoming increasingly aware of in our own habitat.
In addition, as time lapses, the
bacteria naturally found in this nutritive mix of sperm and seminal fluids
begin to multiply at an ever-increasing rate, further adding metabolites that
reduce the pH (a measure of the acidity or alkalinity of a solution), making
the media more acidic. These bacteria are also in competition for the same nutrients
as the sperm cells. Together these two factors, left unchecked, will eventually
lead to the destruction of the fragile sperm.
For ejaculates to be kept for more
than half an hour, counteractive measures to these and other detrimental
conditions should be taken.
The first line of defense is to cool
the temperature of the semen to slow the metabolic rate. To do this and prevent
cold shock, the change in temperature should be regulated to drop at a rate of
about 1 degree Fahrenheit per minute until the solution reaches refrigerator
temperature which is about 39 degrees Fahrenheit).
One way to do this is to take the
semen which is in a baby bottle or a baby bottle liner and place it in a
container of warm water. The water needs to be the same temperature as the
semen. Place this unit in the refrigerator. The water bath will slow the
cooling rate of the semen to about the correct level.
Cold shock can be further reduced by
increasing the volume of the sample through the use of a prepared solution
(semen extender). The sperm should be placed in the appropriate extender medium
before cooling. The correct procedure is to warm the extender and the ejaculate
to the same temperature. Mix and then cool the extended semen at the rate given
above.
The extender medium can also be
designed to help control the deleterious effects of the acid and bacteria. The
addition of proteins to the solution will create a mild buffering of the acid.
Antibiotics in the extender will help limit the replication of the bacteria.
Many great equine semen extenders are
readily available from companies dealing in AI products and equipment. Some of
the best available are easily used powders that are reconstituted using
distilled water.
Remember that time determines which
factor is most lethal to sperm cells. Initially, acidity is the biggest problem
counteracted by the proteins in the extender. After 24 hours, however,
significant sperm death can be attributed to the build-up of bacteria
populations. Samples that need to be kept longer than 24 hours may need to be
inoculated with antibiotics.
There are other reasons to have more
pathogen-free samples. For example, some mares seem to have little resistance
to pathogens found in semen. For these mares, it may be desirable to use
artificial insemination techniques with semen incubated in an antibiotic
extender to retard the growth of these negative bacteria.
Unfortunately, however, our
ever-fragile equine sperm cells also find these antibiotics detrimental to
their health. So the extender must balance the positive effect of the
antibiotics against the bacteria versus the negative effects of the drug on the
sperm cells themselves. Most available extenders today have antibiotics
included that have no or minimal deleterious effects on the sperm.
Nutrition for the sperm cells and
obtaining the proper osmolarity of the liquid are two
other considerations in the development of a proper equine extender media. This
has been taken into account with all commercially available extenders on the
market today.
Today, the male sperm of many species of
animals, including the horse, can be stored, shipped and even frozen for future
use. Today the stallion seed, designed to live 24 to 72 hours once deposited in
the reproductive tract of the mare, can be extended and placed in a
refrigerator where it is likely to remain capable of fertilizing an ovum for 48
hours.
Even longer storage can be obtained by
freezing the sperm at very low temperatures. The major difficulty in this
delicate procedure is the formation of ice crystals as the liquid changes into
the solid state as the temperature drops to -196 degrees Celsius.
The addition of an ingredient such as
glycerin will prevent crystal formation by causing the liquid to freeze in
sheets----a consequence that renders less damage to sperm cells. At best, one
should expect that freezing semen will reduce the number of live normal cells
by 50 percent.
The number of live normal cells in an
ejaculate is an extremely important number in the calculation of the number of
mares that can be inseminated from a collection.
Research has shown that it takes
approximately 500 million live normal cells deposited in the uterus of the mare
to present the best opportunity for a pregnancy.
The following formula can be used to
determine the number of farm mares that can be bred from one fresh ejaculate.
Percent Live Cells X
Volume X Concentration X Normal Cells
500 X 106 (10 to the 6 power)
For the purpose of this discussion,
let's suppose that this ejaculate had 50% live cells, the volume was 100 cc
with a concentration of 250 x 106, and 90% of the live cells were
normal. Put these values in the above formula.
Calculate:
0.5 x 100 x 250 x 106 x 0.9
500 X 106
…and we can see that this ejaculate has the potential to
breed about 22 mares.
In addition, we know that each
insemination procedure is best performed with at least 10cc of fluid. Therefore
to breed these 22 mares, we need a total volume of 220 cc.
The addition of 120 cc of extender to
the 100 cc of raw semen will supply the additional fluids.
Now let’s assume that we are going to
prepare this ejaculate for shipment. We can expect about 50% death loss during
overnight delivery so this ejaculate should be capable of breeding
approximately 11 shipped semen mares.
Semen also ships better in more fluid
so let’s assume that we are going to ship about 30cc per insemination dose.
This means that we need a total of 330 cc of semen and extender. The ejaculate
is 100 cc so 230 cc of extender needs to be added to the ejaculate in order to
make 11 doses of 100 million live normal cells in 30cc of fluid.
There are many advantages associated
with breeding with collected semen.
Stallions with a large book of mares
often have more than one mare ready to breed on any given day. Collecting and
extending the ejaculate allows several mares to be bred from a single
collection. This saves stallion power and presents the opportunity for more
pregnancies. It would be a major feat for a stallion to service 3 mares a day
for any extended period of time.
Extended cooled semen also provides
the opportunity to book the stallion to mares outside the immediate area.
There are many stallion semen shippers
on the market.
Shipping stallion semen can be as easy
as filling a syringe with the extended semen, placing the syringe in the
shipping container, having the container picked up by an overnight delivery
service that will deliver the semen to the mare owner the next day.
The skill in breeding with shipped
semen falls mainly to the breeder of the mare.
The reproductive specialist in charge
of the mare is responsible for calling for the shipment so that the semen will
be there when the mare is ready to ovulate.
The job of the stallion owner or
manager is to provide the mare owner with a semen dose that has at least 500
million live normal cells upon arrival. Using the techniques that have been
discussed provides the stallion manager with the ability to get semen to the
mare owners that is capable of creating a pregnancy.
Summary of the use of Shipped Cooled Semen
Use of Shipped Cooled Semen
A. Sending from Stallion
1. Normal
collection procedure
2. Determine
insemination dose for single mare (500 million progressively motile sperm).
3. Prepare two
doses
4. Place into Equitainer or similar device which will cool semen to 4-8
degrees centigrade. (This is the same as a normal refrigerator.)
5. Ship to
destination via air transport. (Usually arrives within 24 hours; semen will be
viable for 72 hours.)
B.
Arriving for Mare
1. Have courier
pick up from airport.
2. Preplanning should leave you with a mare that
is in estrus and ready to ovulate within 24 to 48 hours.
3. Inseminate mare with one dose immediately
and one dose within the next 24 to 48 hours depending on ovulation
determination.
4. HCG (human chorionic gonadatropin)
often used to stimulate the mare to ovulate within 24 to 48 hours
C. Use of Frozen Semen
This technique is successful, but is
not as successful as using cooled, shipped semen at this time. The technique is
being perfected and may eventually take over the shipment of cooled semen,
which would allow for much less preplanning and deadlines.
ASSIGNMENT (No Quiz)
Send your
report to Dr. Sales at jsales@horsecoursesonline.com
Include
your full name and email address on the document.
Please
answer each question as completely as possible. Resources other than the
written text are encouraged as well as personal experiences.
1. When would a cooled, shipped semen program be
used in the horse breeding industry?
2. Describe, in detail and step by step, what
techniques would be followed in order to prepare a semen sample for shipment to
a single mare owner that is anticipating the insemination of that semen into
that mare within 24 hours.