October, 1999 . Volume 22, Number 9 
NCSU Extension Swine Husbandry
October, 1999 . Volume 22, Number 9
That was the question asked of 240 participants at the
IV International Conference of Boar Semen and Preservation in
Beltsville, Maryland. This conference, held August 8-12th,
covered both the technical and practical aspects of swine reproduction
in hopes to aid in the discovery of new breeding technologies.
Nearly 30 speakers from twelve different countries discussed current
research and concepts in semen preservation, artificial insemination
(AI) techniques, boar stud management, AI application, and biotechnology
techniques in swine reproduction.
According to Dr. Wayne Singleton from Purdue University, there
are currently between 115-120 boar studs in the U.S. servicing
nearly 4 million sows. These kinds of numbers reflect about 55-60%
usage of artificial insemination throughout the U.S. How do
these numbers correspond to other countries? Well, considering
the AI is still "under development in the U. S.", only
a handful of countries are utilizing AI more. Norway, in particular,
breeds nearly 90% of their sows artificially. Projections for
the U.S. swine industry into the year 2005 suggest this industry
will cover nearly 80-85% of the sow population, suggesting strong
expansion in the areas of semen production (i.e. boar studs).
One of the major buzz phrases used at this conference was "How
do we reduce sperm numbers per dose and still maintain good reproductive
performance?". Researchers from Germany are trying to answer
this question with hopes of utilizing breeding technologies such
as sperm sexing. The sperm sexing technology, as reported by
Dr. Larry Johnson, USDA, Beltsville, MD, is currently able to
produce about 10 million sorted sperm cells in 1 hour. This number
of sperm is obviously much to slow to practical produces the needed
3 billion spermatozoa for an artificial insemination and thus,
methods to used small numbers of sperm are needed. Dr. Detlef
Rath from Germany, explained that with surgical insemination,
as little as 5 million spermatozoa can be deposited into the sow's
oviduct (site of fertilization) to achieve acceptable litter size
of 7 or 8 pigs. Even though this approach is probably not practical
on most farms, he explained that good fertilization rates can
be achieved using similar numbers of sperm when semen is inseminated
deep into the uterus at the front end of the oviduct using a special
AI catheter equipped with a small camera on the tip. One of the
major questions that was discussed from this research was how
few spermatozoa can be used with traditional inseminations. The
answer: "That depends". Throughout the conference,
research reports emphasized that there are many variables that
can influence optimal sperm number needed in an AI dose. Generally,
if semen will be stored, transported and used 1-4 days after collection,
sperm numbers should not be lower than 3 billion motile cells
per dose. Even though some countries are reporting good fertility
results with AI doses containing 1.5 billion spermatozoa, they
are often using the semen shortly after collection under stringent
quality control. It is doubtful at this time if producers in
the U.S. should lower sperm numbers per dose beyond what is currently
being used (2.5-4 billion) until an accurate method to
insure that at least 1.5 billion viable sperm are being deposited
and retained in the female.
At the end of the conference a panel of participants from the
U. S. as well as Europe were asked their for their opinion on
the most critical needs in swine AI. In summary, they called
for better methods to evaluate boar fertility, improved semen
extenders, and more research on heat detection and timing of inseminations.
Concerning the latter, many speakers felt that in the next few
year methods to decrease the number of inseminations per sow per
year should increase. Currently, on average, sows in the U. S.
receive around 6.5 inseminations per year. Dr. Nicoline Soede
from the Netherlands, emphasized that if producers take the time
to characterize estrus behavior in their herd, fewer and more
accurately timed inseminations could be performed. She stressed
that sows consistently ovulate about 2/3 rds of the way through
standing estrus and in many herds the length of estrus can be
reliably predicted since sows that come into standing heat quickly
after weaning (3-5 days) have longer estrus lengths than sows
that have longer returns to estrus after weaning (6-10 days).
If this relationship is true in your herd as well, then inseminations
can be timed so that 1) they are performed closer to midpoint
of the sows estrus length, and 2) late inseminations at the end
of standing estrus can be avoided (decreases fertlity). She suggested
if producers record weaning to estrus intervals and corresponding
estrus length for about 30 days, a breeding schedule can be established
that will be effective in minimizing AI doses while maintaining,
or even improving reproductive performance. Our laboratory is
investigating sperm longevity in the female tract and I presented
our most recent findings at this conference. Watch for upcoming
issues of Swine News for detailed information on our findings.
Currently, sperm are viable in the female tract for about 24-h,
therefore, insemination intervals shorter that 24-h may not be
necessary on most farms if each AI dose contains an adequate number
of viable sperm. Methods to extend the viability of sperm in
the female are only in development, but if these methods are deemed
successful, lowering insemination numbers so that fewer boars
will be needed to service sows in less time may be possible.
Assessing sperm quality was also discussed thoroughly, however,
other than assessing sperm motility routinely, and morphology
periodically, other practical methods do not appear to be on the
near horizon. Concerning morphologically examinations, computer
assessment of abnormal spermatozoa appears to be possible and
if this technology becomes accurate and affordable, this approach
may be used more widely throughout the semen industry. Other
diagnostic tests such as sperm membrane and structure and integrity
are in development and perhaps in the next five years a reliable
test to assess fertility may arise.
This was the fourth conference on boar semen evaluation and in
the past conference participants felt that more research was being
conducted on improving semen extenders than what is currently
being done. Numerous speakers emphasized that even the "long
term" semen extenders on the market can only provide semen
storage for around 4 days without a significant drop in fertility.
Dr. Don Levis from Nebraska called for more work in this area
because semen in the U.S. is often shipped long distances and
producers often use semen on days 3, 4, and 5 following collection.
He hinted that a true long term extender that is in development
could maintain semen viability for up to 2 weeks and therefore,
we as an industry should not be satisfied with the current status
of semen extenders. One boar stud manager suggested that if semen
fertility could be maintained a solid seven days compared to the
current 4 day window, producers could lower shipping costs substantially
since the number of shipments per week could be cut in half.
Fewer sperm and AI doses add up to fewer boars and consequently
a smaller genetic population to chose from and make improvements
with. Dr. Roger Gerrits, from the USDA addressed this concern
by updating the conference on the establishment of germ cell preservation
center located in Beltsville. This center will house frozen semen
and embryos of various breeds to ensure that the industry can
maintain genetic diversity in the future. This was encouraging,
however, the question of accessibility to these genes arises.
Who can use these stored genetics in the future? The need to
preserve both male and female genetics through cryopreservation
or freezing for long term storage is required to establish this
germ preservation center. With this need, researchers were asked
to increase their efforts to improve fertility results associated
with the use of frozen semen, which is still sub-optimal compared
to the use of fresh semen. Finally, it was evident at this conference,
that more research is currently being conducted on long term embryo
preservation. The results from Dr. John Dobrinsky's lab at Beltsville
(USDA) were encouraging in this area as he explained a new technique
called vitrification or freezing pig embryo's in a solution that
remains in a liquid state even at -196 degrees Celsius. His laboratory
can produce 7-8 live offspring per litter with a conception rate
of around 50%, suggesting that storage and preservation of maternal
genetics is not a thing of the past in pigs but a current technology.
These are a few of latest technologies that are relatively
new to the swine AI industry that are either currently being utilized
or are in development. This conference has been assembling once
every 5 years, however, it was a general consensus that the next
conference will be held just 3 years from now in the Netherlands
because the AI industry is changing so rapidly. If you have any
questions regarding the information presented here, contact me at
919-515-4474 for more details.
Kevin J. Rozeboom