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Topic:Ultrasonography

Ultrasonography is a diagnostic imaging technique utilized in equine medicine to visualize internal structures of the horse's body. This non-invasive method employs high-frequency sound waves to produce images of organs, tissues, and other anatomical features. It is commonly used to assess musculoskeletal conditions, abdominal organs, reproductive health, and cardiovascular structures in horses. Ultrasonography provides real-time imaging, allowing for detailed examination and evaluation of various physiological and pathological conditions. This page gathers peer-reviewed research studies and scholarly articles that explore the application, methodology, and advancements in ultrasonography for equine health assessment.
Relationship between dose of cloprostenol and age of corpus luteum on the luteolytic response of early dioestrous mares: a field study.
Reproduction in domestic animals = Zuchthygiene    November 4, 2011   Volume 47, Issue 4 660-665 doi: 10.1111/j.1439-0531.2011.01940.x
Cuervo-Arango J, Newcombe JR.The objective of this study was to establish and characterize the relationship between the dose of cloprostenol (37.5, 250, 500 and 750 μg) and the age of the early corpus luteum (CL) (80, 88, 96, 104 and 112 h) on the luteolytic response of mares. Behavioural oestrus and ultrasonographic signs of return to oestrus were considered as the occurrence of full luteolysis. A total of 298 mares were divided into groups according to dose of cloprostenol and CL age. There was an effect of dose of cloprostenol (p < 0.001) and age of the CL at the time of treatment (p 0.05); and that of 500 similar...
Failure of antimicrobial therapy to accelerate spontaneous healing of subclinical pulmonary abscesses on a farm with endemic infections caused by Rhodococcus equi.
Veterinary journal (London, England : 1997)    September 15, 2011   Volume 192, Issue 3 293-298 doi: 10.1016/j.tvjl.2011.07.004
Venner M, Rödiger A, Laemmer M, Giguère S.Mass antimicrobial treatment of foals with small ultrasonographic pulmonary lesions is common on farms with endemic disease caused by Rhodococcus equi. The objectives of this study were to compare the relative efficacy of three antimicrobial protocols for the treatment of pulmonary abscesses on a farm with endemic infections caused by R. equi and to determine the frequency of spontaneous resolution of subclinical pulmonary lesions. Foals with ultrasonographic evidence of pulmonary abscesses ≥ 1.0 cm in diameter (n=128) were randomly allocated to one of four equal treatment groups. Animals wi...
Gestational length in Carthusian broodmares: effects of breeding season, foal gender, age of mare, year of parturition, parity and sire.
Polish journal of veterinary sciences    July 5, 2011   Volume 14, Issue 2 173-180 doi: 10.2478/v10181-011-0027-6
Satué K, Felipe M, Mota J, Muñoz A.The length of gestation in Carthusian broodmares was calculated on the basis of 339 spontaneous full-term deliveries taking place in the 8-year period 1998-2005 from 158 broodmares and 29 stallions in a major farm of Spanish horses of Carthusian strain in southern Spain. Ultrasonography was used to determine follicular dehiscence, 1st day of pregnancy and to confirm conception in mares. Mean GL was 332.4 +/- 12.1 days, and a normal interval of 297-358 days was established for this breed. GL records were grouped on the basis of foal sex (colts or fillies), mating month (between November and Jan...
Synoviocoeles associated with the tarsal sheath: description of the lesion and treatment in 15 horses.
Equine veterinary journal    June 13, 2011   Volume 44, Issue 1 71-75 doi: 10.1111/j.2042-3306.2010.00360.x
Minshall GJ, Wright IM.To describe the presentation, clinical, ultrasonographic and endoscopic features associated with a defect in the tarsal sheath wall, to define the cavity created and to describe a method of treatment. Objective: So called 'false thoroughpins' can be caused by defects in the tarsal sheath wall creating a one way valve effect, removal of which could be therapeutic. Methods: Case records and diagnostic images of horses with synoviocoeles associated with the tarsal sheath were reviewed retrospectively and follow-up information obtained. Results: Synoviocoeles were diagnosed in 15 horses. All were ...
Evaluation of experimentally induced injury to the superficial digital flexor tendon in horses by use of low-field magnetic resonance imaging and ultrasonography.
American journal of veterinary research    June 2, 2011   Volume 72, Issue 6 791-798 doi: 10.2460/ajvr.72.6.791
Karlin WM, Stewart AA, Durgam SS, Naughton JF, O'Dell-Anderson KJ, Stewart MC.To evaluate tendon injuries in horses over a 16-week period by use of ultrasonography and low-field magnetic resonance imaging (MRI). Methods: Tendons of 8 young adult horses. Methods: The percentage of experimentally induced tendon injury was evaluated in cross section at the maximal area of injury by use of ultrasonography and MRI at 3, 4, 6, 8, and 16 weeks after collagenase injection. The MRI signal intensities and histologic characteristics of each tendon were determined at the same time points. Results: At 4 weeks after collagenase injection, the area of maximal injury assessed on cross ...
Tenosynovitis of the carpal sheath of the digital flexor tendons associated with tears of the radial head of the deep digital flexor: observations in 11 horses.
Equine veterinary journal    May 27, 2011   Volume 44, Issue 1 76-80 doi: 10.1111/j.2042-3306.2011.00366.x
Minshall GJ, Wright IM.Tears of the radial head of the deep digital flexor (DDF) have not previously been documented. Objective: To describe the presentation, clinical, ultrasonographic and tenoscopic features associated with tears of the radial head of the DDF and to report the results of treatment. Objective: Tears of the radial head of the DDF cause lameness and distension of the carpal sheath of the digital flexor tendons. Removal of disrupted tissue that is extruded into the sheath can result in clinical resolution and restoration of function. Methods: Case records and diagnostic images of horses in which teari...
Evaluation of four techniques for injecting the trochanteric bursa of horses.
Veterinary surgery : VS    April 26, 2011   Volume 40, Issue 4 489-493 doi: 10.1111/j.1532-950X.2011.00828.x
Tóth F, Schumacher J, Schramme M, Hecht S.To describe the anatomic features of the equine trochanteric bursa and to evaluate 4 techniques for bursa centesis. Methods: Prospective, randomized design. Methods: Equine cadavers (n=2) and 20 live horses. Methods: The trochanteric bursae of 2 equine cadavers were injected with latex to identify the boundaries of the bursae. Four techniques for centesis of the trochanteric bursa were evaluated by attempting to inject dye into both trochanteric bursae of 20 live horses. Techniques included injection of the bursa with the limb-bearing weight and injection with the limb nonweight bearing and su...
Description and genetic analysis of three sets of monozygotic twins resulting from transfers of single embryos to recipient mares.
Journal of the American Veterinary Medical Association    April 16, 2011   Volume 238, Issue 8 1040-1043 doi: 10.2460/javma.238.8.1040
Mancill SS, Blodgett G, Arnott RJ, Alvarenga M, Love CC, Hinrichs K.3 sets of monozygotic twins resulting from transfers of single embryos to recipient mares were examined. Results: In all 3 recipient mares with twin pregnancies, only 1 embryonic vesicle was detected before day 25 of gestation. In 1 recipient mare, 2 apparent adjacent vesicles, each containing an embryo with a heartbeat, were visualized on ultrasonographic examination on day 37 of gestation. The other 2 recipient mares underwent ultrasonographic examination on day 30 of gestation, at which time only 1 vesicle and embryo was identified. In these latter 2 recipient mares, however, a thorough ult...
Optimisation of bone marrow aspiration from the equine sternum for the safe recovery of mesenchymal stem cells.
Equine veterinary journal    September 23, 2010   Volume 43, Issue 3 288-294 doi: 10.1111/j.2042-3306.2010.00215.x
Kasashima Y, Ueno T, Tomita A, Goodship AE, Smith RK.Mesenchymal stem cell (MSC) therapy for orthopaedic disease is being used with increasing frequency; there is a need to define a safe, reliable and effective technique for the recovery of MSCs from the sternum of the horse. Objective: To describe an optimised safe technique for obtaining bone marrow-derived MSCs from the sternum of the Thoroughbred horse. Methods: The anatomical relationship of the sternum with the heart and internal anatomy was demonstrated in cadavers. Sternal anatomy was evaluated ultrasonographically and after midline sectioning. Sternebrae were examined histologically aft...
Ascending placentitis in the mare: an update.
Reproduction in domestic animals = Zuchthygiene    July 16, 2010   Volume 45 Suppl 2 28-34 doi: 10.1111/j.1439-0531.2010.01633.x
LeBlanc MM.Ascending placentitis is a common cause of premature birth, abortion and delivery of compromised, ill foals. Recent experimental models have investigated diagnostic procedures and treatment strategies in an attempt to improve live foal rate. Diagnostics such as transrectal and transabdominal ultrasonography are used to evaluate foetal well-being and placental separation, while measurement of plasma progestins or oestrogen identifies a stressed or hypoxic foetus. Treatment is directed at stopping spread of infection, maintaining uterine quiescence and blocking production of pro-inflammatory cyt...
An investigation of the relationship between race performance and superficial digital flexor tendonitis in the Thoroughbred racehorse.
Equine veterinary journal    June 9, 2010   Volume 42, Issue 4 322-326 doi: 10.1111/j.2042-3306.2009.00021.x
O'Meara B, Bladon B, Parkin TD, Fraser B, Lischer CJ.There is limited information regarding the number of races and the period for evaluation of outcome which is critical for assessment of SDF tendonitis treatments. Objective: To evaluate the re-injury rate and racing performance of Thoroughbred racehorses that sustain SDF tendonitis in relation to matched controls in terms of number of races post treatment and maximum racing performance ratings before and after injury. Methods: Clinical records and racing histories of 401 racehorses with a first occurrence of SDF tendonitis diagnosed by ultrasonography. Controls were of the same age, sex and we...
Endocrine alterations around the time of abortion in mares impregnated with donkey or horse semen.
Animal reproduction science    May 27, 2010   Volume 121, Issue 1-2 124-130 doi: 10.1016/j.anireprosci.2010.05.015
Boeta M, Zarco L.The objective of this study was to monitor and compare the concentrations of equine chorionic gonadotropin (eCG), progesterone and estrone sulphate during normal and failed pregnancies of mares impregnated with donkey or horse semen, relating their individual endocrine profiles to the time of pregnancy loss, and to the histopathologic findings in the aborted fetuses and placenta. Mares (n=54) were used, 32 of them impregnated with donkey semen and 22 impregnated with horse semen. Blood samples were taken twice a week from Day 35 to 120 of pregnancy. Ultrasonographic observations of the fetus w...
Rib osteomyelitis in three foals.
Australian veterinary journal    April 21, 2010   Volume 88, Issue 3 96-100 doi: 10.1111/j.1751-0813.2009.00547.x
Neil KM, Charman RE, Vasey JR.Three foals aged between 21 and 44 days were presented for evaluation of pyrexia and lameness. Each had subcutaneous abscessation associated with osteomyelitis of a rib at the costochondral junction and pathological fracture of the affected rib; one foal had more than one rib affected. Other localised sites of infection included other sites of osteomyelitis, omphalophlebitis, uveitis, enterocolitis, and calcaneal bursitis. The subcutaneous abscessation and rib osteomyelitis was treated surgically in two foals. Salmonella typhimurium was isolated from the subcutaneous abscess in one foal and fr...
The effect of platelet-rich plasma on the neovascularization of surgically created equine superficial digital flexor tendon lesions.
Scandinavian journal of medicine & science in sports    March 10, 2010   Volume 21, Issue 4 554-561 doi: 10.1111/j.1600-0838.2009.01070.x
Bosch G, Moleman M, Barneveld A, van Weeren PR, van Schie HT.The repair process of tendon injuries, which are common in both human and equine athletes, is slow and the quality of the repair tissue is often inferior to the original tendon tissue, which frequently leads to re-injury. The relatively poor vascularization of tendons is considered to be one of the reasons for their limited healing potential. Recently, platelet-rich plasma (PRP), an autologous concentrate of platelets, rich in growth factors, has been shown to enhance the repair process of injured tendons. This effect has been ascribed to the high levels of growth factors in PRP, several of wh...
Mastocytoma in the common carpal sheath of the digital flexor tendons of a horse.
Australian veterinary journal    February 13, 2010   Volume 88, Issue 1-2 20-24 doi: 10.1111/j.1751-0813.2009.00534.x
Leadbeater JC, Gutierrez-Nibeyro SD, Brown JA.A 13-year-old Morgan gelding was examined for right forelimb lameness and tenosynovitis of the right common carpal sheath of the digital flexor tendons. The horse had moderate right forelimb lameness at the trot and marked effusion of the right common carpal sheath of the digital flexor tendons. Ultrasonographic examination revealed a soft tissue mass within the proximal pouch of the affected tendon sheath, located adjacent to the distal physis of the radius. Cytology and culture of the fluid revealed a sterile, eosinophilic tenosynovitis. Tenoscopic exploration confirmed the presence of a cap...
Use of quantitative ultrasonography for noninvasive surveillance of the third metacarpal bone in racing and training Thoroughbreds.
American journal of veterinary research    December 3, 2009   Volume 70, Issue 12 1484-1493 doi: 10.2460/ajvr.70.12.1484
Tabar-Rodriguez JJ, Cruz AM, Monteith G, Gordon K, Hurtig MB.OBJECTIVE-To use quantitative ultrasonography to evaluate the association between the speed of sound (SOS) at 9 sites in the third metacarpal bone (MCIII) of racing Thoroughbreds with workload accumulation and the effect that MCIII failure has on this association. ANIMALS-Sixty-two 2- and 3-year-old Thoroughbreds in racing condition. PROCEDURES-Cumulative work index (CWI) was used to calculate total workload (CWI(total)) and also 3 independent CWIs for the various gaits (ie, trot [CWI(trot)], gallop [CWI(gallop)], and race [CWI(race)]) used during training and racing. Speed of sound was monito...
Pyometra and complete vaginal adhesion in a miniature horse.
The Canadian veterinary journal = La revue veterinaire canadienne    December 2, 2009   Volume 50, Issue 9 971-972 
Cozens ER.A 4-year-old miniature horse experienced intermittent episodes of pyrexia, lethargy, and purulent vaginal discharge following dsytocia. Vaginal endoscopy and transrectal ultrasonography revealed a blind-ending vaginal cavity and distended uterus. Surgical treatment was declined and the mare was euthanized. Post-mortem examination confirmed the diagnosis of pyometra and vaginal adhesions. Un cheval miniature âgé de 4 ans a vécu des épisodes intermittents de pyréxie, de léthargie et de pertes vaginales purulentes après la dystocie. Une endoscopie vaginale et une échographie transrectale...
Effect of topical application of 1% diclofenac sodium liposomal cream on inflammation in healthy horses undergoing intravenous regional limb perfusion with amikacin sulfate.
American journal of veterinary research    November 3, 2009   Volume 70, Issue 11 1323-1325 doi: 10.2460/ajvr.70.11.1323
Levine DG, Epstein KL, Neelis DA, Ross MW.To determine whether topical application of 1% diclofenac sodium cream would decrease inflammation at sites of IV regional limb perfusion (IVRLP) in healthy horses. Methods: 6 healthy adult horses (12 forelimbs). Methods: Bilateral IVRLP with 2.5 g of amikacin sulfate was performed twice in each horse, with 24 hours between each session. Horses were treated with topical 1% diclofenac liposomal cream (treated limbs) or a placebo cream (control limbs). All injection sites were evaluated before the first IVRLP session and 24 hours after the second session by means of ultrasonographic examination ...
Postpartum Massive Hematoma within the Broad Ligament of the Uterus in a Broodmare Possibly Caused by Rupture of the Uterine Artery.
Journal of equine science    October 23, 2009   Volume 20, Issue 3 41-46 doi: 10.1294/jes.20.41
Oikawa MA, Nambo Y, Miyamoto M, Miura H, Kikuchi M, Ohnami Y.A broodmare showed mild signs of abdominal discomfort and anemia after normal delivery. Ultrasonographic examination revealed a massive hematoma within the broad ligament adjacent to the uterine horn. Internal bleeding into the peritoneal cavity (hemoabdomen) was not seen. Following treatment, the clinical signs improved. Hemorrhage caused by rupture of the arteries within the broad ligament of the uterus may be a cause of hematoma. Prepartum and postpartum rupture of the arteries supplying the reproductive organs in the mare, which is not uncommon, can be fatal if severe hemoabdomen occurs. I...
Tendinitis of the proximal aspect of the superficial digital flexor tendon in horses: 12 cases (2000-2006).
Journal of the American Veterinary Medical Association    June 2, 2009   Volume 234, Issue 11 1432-1436 doi: 10.2460/javma.234.11.1432
Chesen AB, Dabareiner RM, Chaffin MK, Carter GK.To determine clinical signs, ultrasonographic findings, and outcome of horses with tendinitis of the proximal portion of the superficial digital flexor tendon (SDFT; group A horses) and to compare signalment, horse use, and outcome in these horses with that of horses with tendinitis of the midmetacarpal region of the SDFT (group B horses). Methods: Retrospective case series. Methods: 12 group A horses and 22 group B horses. Methods: Medical records were reviewed for signalment, horse use, and outcome information; data for group A horses also included severity of lameness, diagnostic results, a...
Vascular perfusion of reproductive organs in pony mares and heifers during sedation with detomidine or xylazine.
American journal of veterinary research    January 6, 2009   Volume 70, Issue 1 141-148 doi: 10.2460/ajvr.70.1.141
Araujo RR, Ginther OJ.To assess the vascular effects of detomidine and xylazine in pony mares and heifers, respectively, as determined in a major artery and by extent of vascular perfusion of reproductive organs. Methods: 10 pony mares and 10 Holstein heifers. Methods: Pony mares were assigned to receive physiologic saline (0.9% NaCl) solution (n = 5) or detomidine (3.0 mg/mare, IV; 5). Heifers were assigned to receive saline solution (5) or xylazine (14 mg/heifer, IM; 5). Color Doppler ultrasonographic examinations were performed immediately before and 10 minutes after administration of saline solution or sedative...
Erythrocytosis and pleural effusion associated with a hepatoblastoma in a Thoroughbred yearling.
Australian veterinary journal    August 5, 2008   Volume 86, Issue 8 329-333 doi: 10.1111/j.1751-0813.2008.00299.x
Axon JE, Russell CM, Begg AP, Adkins AR.A 10-month-old Thoroughbred filly was presented with a 2-month history of recurrent fever and pleural effusion. Major clinical findings were pyrexia and congested mucous membranes. Clinical pathology tests revealed an erythrocytosis, hyperfibrinogenaemia and hyperglobulinaemia. Pleural fluid was seen on ultrasonographic examination of the thorax and analysis of a thoracocentesis sample indicated a lymphocytic, modified transudate. A transtracheal aspirate was normal. The erythrocytosis persisted despite IV fluid therapy. Arterial blood gas analysis and bone marrow aspirate were normal. These f...
Obstructive urolithiasis, unilateral hydronephrosis, and probable nephrolithiasis in a 12-year-old Clydesdale gelding.
The Canadian veterinary journal = La revue veterinaire canadienne    April 9, 2008   Volume 49, Issue 3 287-290 
Macbeth BJ.A 12-year-old Clydesdale gelding was presented for colic and dysuria. Obstructive urolithiasis and chronic renal disease were diagnosed via transurethral endoscopy and percutaneous ultrasonography. Nephroliths, hydronephrosis, and peri-ureteral fibrosis were present. Surgical intervention was declined and the gelding was managed medically with antibiotics and dietary modification. Urolithiase obstructive, hydronéphrose unilatérale et lithiase rénale probable chez un Clydesdale hongre âgé de 12 ans. Un Clydesdale hongre âgé de 12 ans a été présenté pour colique et dysurie. Une urolit...
Uterine blood flow and perfusion in mares with uterine cysts: effect of the size of the cystic area and age.
Reproduction (Cambridge, England)    February 22, 2008   Volume 135, Issue 4 541-550 doi: 10.1530/REP-07-0447
Ferreira JC, Gastal EL, Ginther OJ.Transrectal color and power Doppler ultrasonography was used to study uterine blood flow and perfusion in mares with and without uterine cysts. Vascular perfusion of the uterus and blood flow velocities, vascular perfusion, diameter, circumference, and area of a cross section of the mesometrial attachment were evaluated. To study the effect of internal cysts, two matched groups (cystic and control, n=21 mares/group) were used. Uterine vascular perfusion in mares with cysts was less (P<0.0001) in the cystic than the noncystic region and less (P<0.0009) than that for controls. Mares with c...
Roles of thromboxane A2 and 5-hydroxytryptamine in endotoxin-induced digital vasoconstriction in horses.
American journal of veterinary research    February 5, 2008   Volume 69, Issue 2 199-207 doi: 10.2460/ajvr.69.2.199
Menzies-Gow NJ, Sepulveda MF, Bailey SR, Cunningham FM, Elliott J.To evaluate the roles of 5-hydroxytryptamine (5-HT), thromboxane A2 (TxA2), and platelet-activating factor (PAF) in endotoxin-induced digital hypoperfusion in horses. Methods: 6 healthy adult Thoroughbreds. Methods: Horses were treated with IV administration of saline (0.9% NaCl) solution (control treatment) or the 5-HT 1B/D selective antagonist, GR55562 (0.3 mg/kg), prior to tryptamine infusion (1.6 microg/kg/min for 30 minutes) to establish an effective GR55562 dose. In a crossover study, horses were treated with IV administration of saline solution (control treatment), aspirin (4 mg/kg, 2 h...
Retrospective study of palmar/plantar annular ligament injury in 71 horses: 2001-2006.
Equine veterinary journal    January 4, 2008   Volume 40, Issue 3 237-244 doi: 10.2746/042516408X271217
Owen KR, Dyson SJ, Parkin TD, Singer ER, Kristoffersen M, Mair TS.Constriction of the digital flexor tendon sheath (DFTS) and its contents by the palmar/plantar annular ligament (PAL) is well recognised. However, primary injury of the PAL has not been well documented. Objective: To describe the clinical features of PAL injury, determine its prevalence with or without subcutaneous fibrosis and/or concurrent injury within the DFTS, and assess response to treatment. Methods: Horses were selected for inclusion based upon clinical features consistent with PAL injury and the presence of a thickened PAL (> or =2 mm) verified ultrasonographically. A retrospective...
Dorsolateral approach for arthrocentesis of the centrodistal joint in horses.
American journal of veterinary research    September 4, 2007   Volume 68, Issue 9 946-952 doi: 10.2460/ajvr.68.9.946
Just EM, Patan B, Licka TF.To develop a dorsolateral approach to the centrodistal (distal intertarsal) joint in horses and compare its success rate with that of the traditional medial approach in that joint. Methods: 25 cadaveric equine hind limbs, ultrasonographic images, and radiographic views of the tarsal region of 5 and 59 healthy horses, respectively, and 22 horses with a clinical indication for centrodistal joint centesis. Methods: The dorsolateral approach was established anatomically (3 cadaveric limbs), ultrasonographically (5 horses), and radiographically (59 horses). Centrodistal joint arthrocentesis was per...
Scintigraphic evaluation of the proximal metacarpal and metatarsal regions of horses with proximal suspensory desmitis. Dyson SJ, Weekes JS, Murray RC.The aim of the study was to characterize radiopharmaceutical uptake patterns in horses with clinical and ultrasonographic evidence of proximal suspensory desmitis. It was hypothesized that radiopharmaceutical uptake in the proximal palmar (plantar) aspect of the third metacarpal (metatarsal) bone would be greater in lame limbs of horses with proximal suspensory desmitis than in sound limbs and that there would be a positive correlation between the severity of ultrasonographic abnormalities and the degree of radiopharmaceutical uptake. Nuclear scintigraphic evaluation of the proximal metacarpal...
Successful timing of ovulation using deslorelin (Ovuplant) is labour-saving in mares aimed for single ai with frozen semen.
Reproduction in domestic animals = Zuchthygiene    November 17, 2006   Volume 41, Issue 6 535-537 doi: 10.1111/j.1439-0531.2006.00709.x
Hemberg E, Lundeheim N, Einarsson S.To minimize the number of matings/inseminations, controlled ovulation has been practised since a long time ago. A potent short-term implant, releasing the GnRH analogue deslorelin (Ovuplant((R))) has been used in Australia and North America for several years for hastening the ovulation time in mares, but the product is not registered on the European market. This study was aimed to investigate: (1) ovulation time in mares implanted with Ovuplant when the largest follicle was 42 mm or more in size, (2) repeatability of ovulation time in successive oestruses when treated with Ovuplant, (3) pregna...
Influence of immunization against GnRH on reproductive cyclicity and estrous behavior in the mare.
Theriogenology    June 15, 2006   Volume 66, Issue 8 1866-1875 doi: 10.1016/j.theriogenology.2006.04.038
Imboden I, Janett F, Burger D, Crowe MA, Hässig M, Thun R.The aim of this study was to evaluate the effect of active immunization against GnRH on ovarian activity, plasma progesterone and estradiol concentrations and on estrous behavior in adult mares. Eighteen cyclic mares were randomly divided into a treatment and control group. Nine mares were immunized twice with 2 mL (400 microg GnRH-protein conjugate) of a GnRH-vaccine (Improvac, CSL Limited, Australia) administered intramuscularly, 4 weeks apart. Control mares received the same amount of saline solution. Ovaries and uterus of all mares were examined weekly by ultrasonography from 3 weeks befor...