|
| |
Nurturing maximal reproductive
performance is much more than a 'diagnosis and treatment' approach.
As is the case with males, female reproduction is in part dependent upon
proper nutritional support, adequate exercise, and minimizing stress.
Unlike males, we are rarely concerned about 'promotion' of the animal's
attributes (with the exception of offspring or embryo sales), and thus
focus on individual aspects of pre-breeding management, conception,
pregnancy support, delivery (parturition), and dam/neonatal aftercare.
Pre-breeding management includes the evaluation of the dam's prior
reproductive history, particularly if there have been any past
difficulties. We then evaluate her current condition, and make amends if
any updating of health care or nutritional condition is advisable.
Females of most species are most fertile if on the "thin side of
normal", but in the process of gaining weight. This is not always an
attainable goal; it takes time to thin down obese individuals, and you
can't keep a dam that repeatedly fails to conceive on a rising plane of
nutrition, either.
Nurturing conception boils down to putting high-quality semen into the
proper place at the proper time, and into an environment ready to
receive it. We may need to monitor the dam for potential infections,
treat a variety of reproductive problems medically, alter nutrition, and
on rare occasions even recommend changing sires (occasional antibody
problems can develop with repeated exposure to sperm from the same
sire). Above all, we must monitor the estrus cycles and behavior of the
dam, as her interest in the process lets us know when to get involved.
At our facility, we have resident "teasers"; a pony stallion, bulls, and
a "cystic" cow; whose job it is to assist us in monitoring the
oftentimes subtle changes in behavior exhibited by our patients.
Observation of that behavior, even at night, is a critical part of our
job, and in ultimate success rates.
Once our patient is pregnant, most are taken home by their owners. Upon
departure, we supply a custom schedule of recommended pre-delivery
health care procedures, and a predicted "due date". At least one
"recheck" assessing the progress of a pregnancy, particularly in the
first trimester, is often recommended, as it is during the earliest
weeks that pregnancy loss is most likely. The development of an embryo
from conception to birth is still a little-understood process, but does
involve a continuous and evolving "communication" between embryo and
maternal uterus prior to implantation. It is during this early stage
that "errors of communication" can end the process, and thus a basic
explanation for why pregnancy losses are most likely early on.
Minimizing stress to the dam is an important supportive action during
this period. For example, mares who are difficult and nervous 'haulers'
are best advised to 'stay put' until 50 or more days along, and
providing adequate shade and cool water during hot summer weather to
cows and ewes can dramatically improve pregnancy rates.
Parturition, the most important moment in the eyes of most owners, is
certainly a momentous event for the participants as well. While nature has developed a surprisingly trouble-free
system for this, problems can and do occur. Valuable animals may be
monitored at this critical time, should assistance be necessary, and we
offer this service with veterinary attendance 24 hours per day. Because
too much attention and human presence near the dam close to delivery can
actually enhance the liklihood of complications by making her nervous,
we monitor our patients 'remotely', by the use of video cameras and/or
tiny, radio-transmitter alarm systems, secured to the vulva long before
delivery. With a typical foal delivery, for example, which is most
likely to occur between midnight and 3 a.m., early dilation will set off
the radio transmitter, sounding an alarm which awakens the veterinarian
in attendance. The progress of the delivery can then be monitored
through the video cameras, eliminating the need for disturbance of the
mare unless absolutely necessary. Once the foal is delivered, initial
treatment of the umbilical stump and close-up assessment of both mare
and foal can be quietly accomplished while the mare is resting.
Postpartum management involves initial assessment of the physical
condition of the newborn, treatment of the umbilical stump with a
non-irritating disinfectant to prevent 'navel-ill', examination of the
dam to be sure that colostrum production and nursing are normal, that no
damage to the reproductive tract occurred, and that the placenta is
passed intact. Most owners requesting monitored parturition also want us
to spend time during those first hours and days "imprinting" the
offspring, a gentle handling process which rapidly accustoms the newborn
to human presence and handling without disrupting the normal interaction
with the dam. Of course this is not easy to do if the dam does not feel
comfortable with the person doing the "imprinting", hence the
importance of allowing the expectant mother time to "settle in" at our
facility prior to delivery. So little time
spent with the offspring right after birth, makes it so much easier to
work with the animal throughout the rest of its life. If you don't
believe this, come visit, and ask to take a look at Gambler ET, our
first frozen embryo transfer. Now a 2000 pound bull, he comes when
you call him, is halter broke, picks up his feet like a horse, can be
ridden without any halter or bit (we'll let you go for a ride!), and
even provides semen samples with just a plastic bag...........
Further services may involve rebreeding the dam, performing the initial
series of vaccinations of the young offspring, and further handling or
training of the youngster. Most of our handling and training procedures
are included in our Board fees, and are not at extra charge.
One of our more recently introduced procedures is the surgical reduction
of equine twins where pregnancy has advanced beyond the 28 to 30 day
stage, when the embryos become too large to successfully be reduced
through the nonsurgical "pinch" method. Those familiar with horse
breeding know that about 25 percent of all conceptions are believed to
initially be twins, and that typically this number is naturally reduced
to a single fetus by day 35. Twin pregnancies in mares that are carried
beyond this stage are almost always aborted later in gestation, with
only about one in ten thousand births actually resulting in live twins.
If we can, we thus want to "abort" one of the twins in order to save the
other.
This can be accomplished with about a 75% success rate prior to 28 days
of pregnancy by a simple "pinch" technique, involving isolation of the
embryo judged least likely to survive by ultrasound and manual
palpation, then crushing the conceptus by manual pressure per rectum.
This is done without anesthesia, and normally without sedation, as there
is no discomfort to the mare involved. Once the pregnancy proceeds
beyond 28 days, however, the success rates (determined by survival of
the untouched conceptus) drops dramatically with each additional day (to
zero after 33 days of gestation), as the local inflammatory response
subsequent to the loss of the pinched twin becomes so great that both
embryos succumb. Sometimes, for various reasons, twins may not be
discovered until well after this window of opportunity.
A more exotic technique employed with some success the past few years in
pregnancies further advanced, has been the ultrasound guidance of a long
needle through the cranial vaginal wall, through the uterine wall, and
into the object fetus' heart, where a small amount of sterile potassium
chloride is injected. This potassium overload stops the heart of the
fetus, and that fetus "mummifies", allowing the twin to proceed with
development. This, however, is a difficult procedure to do, as the
needle is introduced more or less parallel to the structures involved,
not at right angles to it. Also, the object fetus is typically at least
15 inches away from the surgeon, and there is less room to maneuver
within the pelvic cavity.
Dr. Mennick attempted this technique once, and finding it too difficult
to comfortably perform on his patients, devised an alternative method
that has worked well, takes significantly less time, and seems no more
stressful to the patient. This also involves a surgical approach with a
long needle, but through the left flank, not the reproductive tract. A
traditional, surgical approach is used in the standing horse, using only
sedation and local anesthetic. Wearing a sterile sleeve, of course, the
surgeon can quickly reach into the abdomen, locate the selected fetus,
and regardless of which uterine horn it is in, retract it close to the
incision. By this method, the fetus is firmly grasped and controlled,
and the approach with the needle is at right angles to it. Injection may
be performed anywhere in the thoracic or abdominal cavity with success;
the average amount of time involved in the mare's abdomen is just a
minute or so, as opposed to possibly several exasperating hours by the
other technique.
To date, five of these procedures have been performed, ranging from 64
to 92 days of gestation. In one case, the pregnancy was advanced enough
that the uterus was too large to allow adequate stabilization of the
selected fetus, and proper injection was not possible. The mare went on
to deliver two live twins. In one instance, both fetuses were
subsequently lost, and the remaining three were completely successful, i.e. the
selected fetus was mummified, the remaining fetus went on to experience
normal, healthy delivery, and the mare experienced no complications
whatsoever.
At this point, we advise that the patient be evaluated for this
procedure as soon as possible after 60 days, and that much after 90 days
it may be more difficult and less successful.
|
|
