EQUINE | Equine Disease Quarterly
Research that makes it possible to separate x- and
y- bearing sperm through flow cytometry (based on
the fact that x-bearing sperm contains more DNA),
has been commercialized and is currently offered by
specialized laboratories. The method is very accurate,
but efficiency is still quite low and results in a low
number of sex-sorted sperm. This hurdle has been a
limiting factor for the method and more research is
needed to improve the technique. Recent research
exploring the use of nanotechnology to target specific
sperm DNA sequences has the potential to develop
a new efficient technology to select sperm for sex-
sorting, and maybe more importantly—to select
sperm based on other genetics that can be used as
a replacement or complement to pre-implantation
genetic testing of embryos. Preliminary results from
studies using nanotechnology for sex-sorting in
donkeys and other species appear to be promising.
Logically, technologies that involve sperm selection in
the laboratory will always result in limited number of
sperm that can be used for breeding. However, recent
scientific and clinical advances make it possible to
use a single sperm from an infertile stallion and inject
it into an egg that has been retrieved by ultrasound
guided follicular aspiration from the ovary, culture the
conceptus in a petri dish under controlled conditions
and transfer the embryo into a recipient mare or back
into the same oocyte donor mare at a later time.
Intracytoplasmic sperm injection (ICSI) has become
increasingly popular and a suitable method to use
genetically valuable semen of poor quality or with
restricted access because of disease or death of the
stallion. Research to improve the efficiency of this
technology would greatly benefit breeding operations
that allow assisted reproduction.
Few, if any, breed registries accept foals resulting from
somatic cell cloning of an existing individual. The
technology is nevertheless offered for horses, and has
become popular among some horse owners that don’t
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need to register their foals. Although cloned horses
have been used successfully as athletes, the greatest
benefit of the technology may be the possibility to
produce an intact stallion as a genetic copy of an
existing gelding with a successful athletic career. It
should be kept in mind that even if the genetic make-
up of the cloned copy is identical to the original
horse, the phenotype (looks and performance) may be
different because of the influence of the environment
that the embryo and fetus were exposed to in the test
tube and uterus of the surrogate mother (epigenetics).
The best prospective for the cloned intact stallion may
therefore, be for breeding purposes. In other words—
an expensive way to put testicles back on a gelding.
CONTACT:
Mats H.T. Troedsson, DVM, PhD, DACT, DECAR
[email protected]
(859) 218-1133
Maxwell H. Gluck Equine Research Center
University of Kentucky
Lexington, KY
Clostridial Myositis
Clostridial myositis is a rare but serious bacterial
infection, which causes inflammation and death
of muscle and release of bacterial toxins into the
bloodstream. This condition is also referred to as
myonecrosis, malignant edema, and gas gangrene. It
occurs most often in horses that have recently received
an intramuscular injection. Clinical signs appear 6-72
hours following the injection, and horses initially exhibit
acute swelling, heat, and pain of the affected area. The
disease progresses rapidly and the horse’s condition
may decline within hours. The affected animal exhibits
signs of systemic toxemia; death can supervene rapidly
in severe cases. Clostridial bacteria produce gas that
results in a characteristic emphysematous (bubbly)
feel or crepitation of the region. Clostridial myositis
• Equine Health Update •