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- Author or Editor: Edward L. Squires x
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Abstract
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 cycles.
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 control mares.
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 Assoc 2001;218:749–752)
Abstract
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.
Design—Prospective study.
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.
Abstract
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 mares.
Design—Prevalence survey.
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 were recorded.
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; 0.9%).
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 2000;217:58–63)
