Objective—To evaluate gonadotropin secretion and
ovarian function after administration of deslorelin
acetate to induce ovulation in mares.
Design—Randomized controlled trial.
Animals—16 healthy mares with normal estrous
Procedure—8 control mares were allowed to ovulate
spontaneously, whereas 8 study mares received
deslorelin to induce ovulation when an ovarian follicle
> 35 mm in diameter was detected. Follicle development
and serum concentrations of gonadotropins
were monitored daily during 1 estrous cycle. Pituitary
responsiveness to administration of gonadotropinreleasing
hormone (GnRH) was evaluated 10 days
after initial ovulation.
Results—Interovulatory intervals of mares treated
with deslorelin (mean ± SD, 25.6 ± 2.6 days) were
longer than those of control mares (22.9 ± 1.8 days).
Diameter of the largest follicle was significantly smaller
during 2 days of the diestrous period after ovulation
in deslorelin-treated mares than in control mares.
Concentrations of follicle-stimulating hormone (FSH)
were lower in deslorelin-treated mares on days 5
through 14 than in control mares. Concentrations of
luteinizing hormone were not different between
groups during most of the cycle. Gonadotropin
release in response to administration of GnRH was
lower in mares treated with deslorelin acetate than in
Conclusions and Clinical Relevance—Administration
of deslorelin was associated with reduction
in circulating concentrations of FSH and gonadotropin
response to administration of GnRH during the
estrous cycle. Low concentration of FSH in treated
mares may lead to delayed follicular development and
an increased interovulatory interval. (J Am Vet Med
Objective—To determine the impact of antimicrobial-containing semen extender on the growth of Taylorella equigenitalis in semen culture-positive for contagious equine metritis (CEM) and the development of CEM after artificial insemination with CEM-positive semen extended with antimicrobial-containing semen extender.
Animals—21 mature mares free of CEM, 1 mature stallion experimentally infected with CEM, and semen from a stallion naturally infected with CEM.
Procedures—CEM-positive semen was incubated in semen extender with and without antimicrobials (amikacin [final concentration, 1 g/L] and penicillin G potassium [0.63 g/L]) followed by determination of the number of colony-forming units of T equigenitalis. Mares were inseminated with raw, extended, or cryopreserved semen culture-positive for T equigenitalis and observed for clinical signs of CEM. Samples for bacterial culture were obtained from the uterus, clitoral sinuses, and clitoral fossa of mares 7, 14, and 21 days after artificial insemination.
Results—Antimicrobial-containing semen extender significantly reduced the number of colony-forming units of T equigenitalis in CEM-positive semen. Artificial insemination with raw CEM-positive semen resulted in clinical signs of CEM, whereas artificial insemination with extended or cryopreserved CEM-positive semen did not result in clinical signs of CEM.
Conclusions and Clinical Relevance—Antimicrobial-containing semen extender significantly reduced the risk of dissemination of CEM. The inclusion of amikacin (1 g/L) and penicillin G potassium (0.63 g/L) in extended semen reduced the transmission of CEM from stallions to mares during artificial insemination, which may result in altered dissemination of the disease.
Objective—To determine the incidence, ultrasonographic
characteristics, and risk factors associated
with embryonic development characterized by formation
of an embryonic vesicle without an embryo in
Animals—159 pregnant mares.
Procedure—From 1994 to 1998, mares between 11
and 40 days after ovulation with normal and abnormal
embryonic development were examined ultrasonographically,
and characteristics of each conceptus
Results—The incidence of abnormal embryonic
development in mares characterized by formation of
an embryonic vesicle without an embryo was 7/159
(4.4%) during the 5 breeding seasons. Age and breed
of mare or type of semen used did not differ for
mares with normal and abnormal embryonic development.
The percentage of mares in which the conceptus
was undersized during ≥ 1 examination was significantly
higher for mares with abnormal conceptuses
(5/7), compared with mares with normal conceptuses
(2/147; 1.4%). The percentage of examinations
during which the conceptus was undersized was significantly
higher for abnormal conceptuses (12/27;
44.4%), compared with normal conceptuses (4/448;
Conclusion and Clinical Relevance—To diagnose
an embryonic vesicle without an embryo, mares
should be examined by use of transrectal ultrasonography
on day 25 after ovulation. When an embryo cannot
be identified at that time, mares should be reexamined
at intervals of 1 to 3 days until day 30.
Because undersized conceptuses are more likely to
be abnormal, development of undersized conceptuses
should be monitored closely. (J Am Vet Med Assoc