The Stallion
By Karen Berk
|
Stallion
ads in all the magazines lead us to believe this breeding business is simple
and foolproof. Pick a stallion, order semen, ship, and in the appropriate time
span...a foal. Well...sometimes.
With the radical changes in
reproductive technology in the past 20 years, small breeders are no longer
limited by geographic proximity. Once only wealthy breeders could ship mares
cross country to a perhaps superior stallion. Today thanks to artificial
insemination (A.I.), overnight delivery and cooled or frozen semen, we have
broken the barriers of stallion selection with the exception of stud fees.
However, having easy access to top quality stallions does not mean getting your
mare in foal is easy or inexpensive. First, a healthy and fertile stallion is
essential for an equine breeding program to be successful. And no less
important is an experienced and educated stallion management team.
The unfortunate practice of keeping show stallions under lights year
round to maintain impressive coats is a strong and growing reason for low
libido and decreased fertility in top stallions. While it does no harm to
keep mares under lights year round, maintaining cycles and getting a great show
coat, stallion reproduction must undergo a low photo period hiatus. Natures
cycling for the stallion requires a near shutdown period which is triggered by
the pineal gland behind the eye. Fall and Winter's short daylight hours trigger
a type of hibernation for the endocrine system. Come Spring, as light hours
increase, the reproductive system builds up once again for the equine's natural
season, late Spring and Summer. This does not coincide with our current policy
of producing foals as close to January 1 as possible. I do not believe either
trainers, owners or most breeding managers are aware that this tradition of
year round lights is doing possible damage after long exposure. Current studies
at Universities have exposed these facts in the last number of
years.
Because the stallion makes up 50% of each conception, his
fertility is as important as the reproductive capacity of each individual mare
in the program. The selection of the stallion is commonly done, in the United
States, on the basis of pedigree and performance, with little consideration
being given to the individual's reproductive capability. While the Europeans
have been doing a stallion selection process, demanding a minimum or
reproductive efficiency, for years. This has produced, in general, a higher
quality of reproductive individual.
The most reliable measure of
fertility in a stallion is the number and percentage of mares he settled in a
season. These figures are not always available. Additionally, previous history
will not be possible in a rookie stallion.
If one is to truly
understand the stallion's role, in the reproductive process, one must be
familiar with his anatomy and endocrine system. How it correlates to conception
and fertility is paramount in seeing the whole picture of your potential
breeding stallion.
The male reproductive organs consist of 2 testes,
each suspended by a spermatic cord and external cremaster muscle, 2
epididimides, 2 defferent ducts, each with an ampula, paired vesicular glands,
a prostate gland, paired bulbourethral glands and the penis. Most breeders only
consider the first and last. Additionally, the reproductive tract is supported
within the pelvic cavity by the hammock like genital fold, and externally by
the scrotum.
The endocrine system provides the hormonal fuel for the
above. Stimulated by light, the pineal glad, behind the eye, produces
melatonin. Melatonin stimulates the Hypothalamus , within the brain to produce
GnRH. This in turn stimulates the pituitary to produce FSH and LH. These are
critical for spematogenesis to occur in the testes. Any breakdown of this
sequence shows up as a fertility problem. At any sign of problem with stallion
fertility, one should consider initiating cultures. This should include
cultures of both the semen and the urethra, both pre and post breeding.
Additionally an endocrine panel should be pulled for a complete picture.
The sequence of events to produce normal reproductive function are: a)
sperm are produced in the tubule of the testes; b) they mature and acquire
fertilizing capacity in the head and body of the epididymis; c) sperm cells are
maintained in a fertile state in the tail of the epididymis; d) ejaculated by
the contraction of the deferent ducts, accessory sex glands and muscles
associated with the penis. These processes depend on and are coordinated by the
neuroendocrine system. The process from the start of the creation of the sperm
cell to final maturation in the epididimal tail is approximately 57 days. This
means whatever a stallion ejaculates in February was begun in December. If an
injury or infection, or any occurrence that would raise the temperature of the
testes 2 degrees, were to happen today, this stallion would still be fertile
tomorrow, but would have the possibility of being infertile, temporarily, in 2
months. Many times when a stallion suddenly stops settling mares, after a
number of successful months, breeding managers do not know to look back 60 days
to seek a cause. Perhaps a kick, colic or cold with fever. The problem normally
rectifies itself shortly as soon as new cells are available, assuming there
were no complications or permanent damage to the testes.
Next let's
discuss testicular size. The horse's testes size and circumference are in
direct proportion to his production capacity. A stallion with small testicles
will not be as efficient as one with large. Volume is as important as
concentration and motility in a heavily booked stallion, making daily sperm
production critical for reproductive success.
Assuming we have chosen a
fine stallion of respectable lineage, reputation and credentials, we go on to
collection. There are some stallions who can be collected " on the ground",
that is without mounting. The usual is to have available a mare (preferable in
estrus) or a phantom, also known as a dummy or breeding mount. The stallion
should be washed using warm water, being carful to gently remove the smegma
from both the shaft and prepuce. Often a small accumulation will occur commonly
called a "bean". Since water is spermacidal, let air dry or pat dry with a
clean, white, paper towel. The stallion is then led to the mare or phantom and
when erect, allowed to mount. The qualified technician or Vet will then deflect
the penis into an artificial vagina (A.V.) And the stallion will ejaculate.
Currently there are a number of A.V.'s available. Commonly used are the
Colorado, Hanover, French, Japanese and Missouri. The former being the heavier
but maintaining temperature for longer periods. This is much more important in
the north then southern states during winter and early spring. Usage though is
personal preference, with excellent records for all. The collection is brought
immediately to the lab for evaluation and preparation. In the lab three key
values must be ascertained; 1) Gel Free Volume 2) Concentration 3) Progressive
Motility. Volume is measured, Concentration is deduced by either a
hemocytometer, spectometer, or densimeter, Motility by a phase contrast
microscope with a heating stage. Another key concideration is velocity. The
only sperm that are viable must be traveling in a fairly straight path and are
actually spiraling. This is called progressive motility. Those crazy swimmers
going in circles or erratic patterns must be discounted when deciding the
correct percentage of motility. Often people only factor in dead cells when
discerning percentage. Also, not having a heated stage warmer will shock the
cells, once again giving an incorrect figure. This is critical when figuring
dosage for shipment. A dose must be a minimum of 1 billion progressively
motile cells. The mare receiving this at ovulation has the best possible
chance for conception. In error or greed, the shorting of this amount severely
compromises successful conception.
An unwashed stallion with a dirty
ejaculate will give a false and high concentration number. Since the
instruments that measure concentration, cannot differentiate between particles
of sperm or any other, you get a false high. They only measure density. Often
this is another reason for incorrect dosage and low conception rate. The
exception to this is a Hemocytometer.
Having correctly calculated your
ejaculate, you are now ready to extend the semen and prepare your doses.
Extenders nourish and protect the cells in transport and within the mare. They
are a basic sugar and skim milk base, usually with some form of anti-biotic
added. Shipped semen is extended at a minimum of 4 to 1. Horses with high
concentration levels are extended even further. The doses are then packaged,
placed in a industry approved shipping container, and shipped. I also suggest a
breakdown be included with the shipment, showing Volume, Concentration,
Motility, Time of day collected, Extender brand and ratio of semen to extender.
I highly encourage mare owners to insist on this. If the numbers are not
available, there is little chance the dose is correct and reproductive
efficiency is severely compromised. This translates into DOLLARS AND TIME
LOST.
The stallion manager's ability to communicate and answer questions
may well be one of the important criteria in choosing a stallion. Do not
hesitate to ask for references of shipped semen recipients, and what equipment
they have available in their lab.
Whether you are considering purchasing
a stallion for breeding or contracting for your mare(s) coming season, arm
yourself with as much knowledge as you can. Because a farm may breed multiple
stallions and/or cover many mares, or even ship semen regularly, does not make
them qualified to use your time or money. Remember, the only criteria to
calling oneself a professional is accepting money. Whereas, a qualified breeder
is an educated horseman with the tools, education, success rate, and dedication
to strive for maximum reproductive efficiency. |
|
|
