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Topic:Ultrasound

Ultrasound in horses is a diagnostic imaging technique that utilizes high-frequency sound waves to produce images of the horse's internal structures. It is commonly used in veterinary medicine to evaluate soft tissues, tendons, ligaments, and organs. This non-invasive method allows for real-time visualization of physiological and pathological conditions, aiding in the diagnosis and management of various equine health issues. Ultrasound is particularly valuable for assessing musculoskeletal injuries, reproductive health, and abdominal conditions in horses. This page compiles peer-reviewed research studies and scholarly articles that explore the application, methodology, and advancements in ultrasound technology within equine veterinary practice.
Novel Intracardiac Ultrasound Images Developed on a Cardiac Ultrasound Simulator and Validated in Live Horses.
Journal of veterinary internal medicine    April 24, 2025   Volume 39, Issue 3 e70087 doi: 10.1111/jvim.70087
Vernemmen I, Demeyere M, Van Steenkiste G, Buschmann E, Decloedt A, van Loon G.Ultrasonographic guidance of catheter-based interventions in horses is based primarily on transthoracic echocardiography (TTE). Intracardiac echocardiography (ICE) has the potential to provide detailed imaging of specific cardiac regions. Insight and training in echocardiographic guidance can be acquired using an echocardiography simulator. Objective: Use an echocardiography simulator for horses to determine specific ICE views for catheter-based interventions and validate these in live horses. Methods: Six adult healthy experimental horses. Methods: Observational study. An echocardiographic ph...
A dorsal ultrasound-guided approach to perineural injection of the sixth and seventh cervical spinal nerves in horses is accurate and does not result in epidural placement.
Journal of the American Veterinary Medical Association    April 23, 2025   1-8 doi: 10.2460/javma.25.02.0101
Brown KA, Engiles JB, de Solis CN, Bills KW, Johnson AL, Davidson EJ.To determine the accuracy of a dorsal ultrasound-guided approach for perineural injection of the sixth and seventh cervical spinal nerves (CSNs) with the use of a clinically relevant volume of injectate (2 mL). We hypothesized that the majority of injections would result in identification of contrast solution in the intervertebral foramen (IVF) on CT and corresponding methylene blue dye staining of the CSN on postmortem evaluation, and distribution of injectate into the epidural space would not occur. Unassigned: 7 horses donated to the University of Pennsylvania New Bolton Center for euthanas...
What is the “train track” in the retained equine testis?
Journal of equine veterinary science    April 15, 2025   Volume 149 105573 doi: 10.1016/j.jevs.2025.105573
Giorgio SD, Monti S, Palmieri V, Marino G, Napoli E, Vullo C, Catone G.A 3-year-old Quarter horse stallion with unilateral left cryptorchidism was referred for the absence of the left testis in the scrotal bursa and an enlarged right testis. The ultrasonographic examination revealed the presence of the left testis at the abdominal level. Two small hyperechogenic lines were observed running parallel and resembling a cylindrical cavitary foreign body, within a non-homogeneous area with blurred margins. The testis was removed by laparoscopy and macroscopically, the testis's cut section revealed the presence of two live adult nematodes emerging from 2 mm blood-filled...
Physiological and behavioral parameters of pain and stress in mares during and after transvaginal ultrasound-guided follicular aspiration.
Frontiers in veterinary science    April 9, 2025   Volume 12 1574351 doi: 10.3389/fvets.2025.1574351
Van den Branden E, Salamone M, Broothaers K, Peere S, Polfliet E, Dewulf M, Van Steenkiste G, van Loon G, Smits K, Govaere J.The use of transvaginal ultrasound-guided follicle aspiration (TVA) for oocyte collection has become a widely used procedure in horses for embryo production (IVEP). The TVA procedure is characterized by various manipulations, which are physical restraint, perineal preparation, transrectal palpation, insertion of an intravaginal device, and needle punctures. These repeated transvaginal and transovarian punctures have raised concerns about their potential effects on mare welfare. Our study aimed to investigate the effects of TVA manipulations, and especially puncturing, on pain and stress in ma...
Equine colic: A comprehensive overview of the sonographic evaluation, diagnostic criteria, and management of different categories.
Open veterinary journal    March 31, 2025   Volume 15, Issue 3 1116-1139 doi: 10.5455/OVJ.2025.v15.i3.5
Tharwat M, Al-Sobayil F.Colic or acute abdominal pain is the most prevalent cause of emergency intervention in veterinary medicine, and it has been considered the principal reason for collapse and/or euthanasia in a wide range of studies. The condition may be initiated by a number of different disorders affecting the abdominal viscera, but acute gut disease is the most common etiology in equines showing colic symptoms. of the main goals of colic management is to distinguish between surgical and medical causes, as prompt surgical intervention can significantly improve outcomes for those requiring surgery. Despite the ...
Equine cadaveric study suggests tibial and fibular nerve block is feasible with a single ultrasound-guided injection via a caudocranial midfemoral approach.
Journal of the American Veterinary Medical Association    March 26, 2025   1-6 doi: 10.2460/javma.25.01.0002
Strugava L, Gomes ARC, Lorga AD, Bosak VL, Rossa AP, Janiszewski JDR, Machado M, Dornbusch PT, Moreno JCD.To describe anatomical references and sonoanatomy of an echo-guided injection for blocking the tibial and common fibular nerves with the use of a caudocranial midfemoral approach and to evaluate dye spreading in horse cadavers. Unassigned: 1 horse cadaver preserved in glycerin was used for the anatomical study, and 14 fresh horse cadavers were used for the dye spreading study. The experimental procedures were conducted on the first cadaver on March 25, 2021, and on the last cadaver on October 5, 2022. A glycerin-preserved horse cadaver's pelvic limb was dissected to identify anatomical landmar...
It is not always what it seems: allantochorion cervical pole necrosis.
Journal of equine veterinary science    March 18, 2025   Volume 149 105422 doi: 10.1016/j.jevs.2025.105422
Fischetti L, Perina F, Sarli G, Ellero N, Freccero F, Castagnetti C, Mariella J.A 286-day pregnant mare was referred for signs of impending abortion. The ultrasonographic evaluation revealed a high normal combined thickness of the utero-placental unit (CTUP), oligohydroallantois and a living fetus. No vulvar discharge was observed, and the cervical swab culture was negative. After a choke, the mare received NSAIDs and antibiotics and then developed systemic inflammatory response syndrome (SIRS) and aborted. The amniotic portion of the umbilical cord was excessively long and twisted and the chorionic side of the placenta showed a brown discoloration and rough surface area....
Resistivity and Pulsatility Indexes Renal Values Do Not Differ When Obtained from Abdominal or Transrectal Approaches in Healthy Horses. Rosse NDS, Tavares RA, Nunes MC, de Freitas BW, Reis ECC.Early detection of renal deficient function is imperative for the success of treatments and determining prognosis. In horses, a renal ultrasound can be performed through the abdominal wall (TA) or transrectally (TR), being an important tool for the evaluation of the kidneys. Besides renal morphology, resistivity (RI) and pulsatility indexes (PI) may be early tools to detect renal injury as they reflect arterial compliance. Twenty-nine healthy adult horses were sonographically evaluated by TA and TR approaches, measuring RI and PI on both kidneys. The mean values from the TA for RI and PI in th...
Transvaginal Follicle Aspiration in Mares: A Description of Different Techniques and Comparison of Results Across Different OPU Clinics.
Reproduction in domestic animals = Zuchthygiene    March 9, 2025   Volume 60, Issue 3 e70043 doi: 10.1111/rda.70043
Cuervo-Arango J, Necchi D, Clutton-Brock A, Profaska M, Crabtree J, Claes A.This retrospective clinical study describes different techniques for transvaginal follicle aspiration in mares and compares results from 5 different commercial ovum pick-up (OPU) clinics in which the same operator aspirated mares using different systems and equipment: Clinic 1 (n = 42 mares, two-operator OPU technique, double-lumen-echogenic-tip needle, and manual syringe-assisted flushing of follicles), Clinic 2 (n = 28 mares, single-operator-OPU-technique, double-lumen-echogenic-tip needle, infusion pump controlled by foot-pedal for follicle flushing), Clinic 3 (n = 18 mares, sin...
Analgesic and Gastrointestinal Effects of Morphine in Equines.
Animals : an open access journal from MDPI    February 17, 2025   Volume 15, Issue 4 571 doi: 10.3390/ani15040571
Guzmán JFC, Gontijo AS, Melgaço ES, Faria SA, Baldi MLC, Sousa LN, Wenceslau RR, Fantini P, Xavier ABDS, Beier SL.Morphine has significant clinical and analgesic effects in horses, but its impact on the gastrointestinal tract requires further understanding. This study assessed the analgesic and gastrointestinal effects of morphine in horses undergoing elective orchiectomy in the quadrupedal position. Thirty uncastrated male horses were randomly assigned to three groups: orchiectomy without morphine and sedation protocol (OSM), orchiectomy with morphine and sedation protocol (OM), and administration of morphine alone in the absence of orchiectomy (M). The anesthetic protocol involved acepromazine (0.05 mg/...
Ovarian hemorrhage as the primary cause of hemoperitoneum in cycling and pregnant Miniature Horse mares.
Journal of the American Veterinary Medical Association    February 14, 2025   1-9 doi: 10.2460/javma.24.11.0723
Stricklin OE, McKenzie EC, Sriboonyapirat P, Russell DS, White CN.To determine whether Miniature Horse mares are predisposed to hemoperitoneum from nonneoplastic ovarian hemorrhage and report the clinical characteristics of this disorder. Methods: 51 equines with hemoperitoneum, including 22 nonminiature mares and 9 Miniature Horse mares, identified by searching medical records of a tertiary large animal hospital for confirmed hemoperitoneum cases between 2012 and 2023. Methods: Signs of hemoperitoneum in miniature mares included lethargy, inappetence, colic, tachycardia, and moderate to severe anemia (PCV ranging from 11% to 19%). Five miniature mares did n...
The inability of spectral Doppler ultrasonography to identify stallions with testicular dysfunction.
Journal of equine veterinary science    February 4, 2025   105367 doi: 10.1016/j.jevs.2025.105367
Pozor MA, Macpherson ML, Kelleman AA, Smith H, McNaughten JW.This retrospective study aimed to validate the usefulness of spectral Doppler ultrasonography in diagnosing testicular dysfunction in stallions. The first part of the study included a pony stallion with age-related testicular degeneration (18 - 21 yrs. old). Testicular dimensions, spectral Doppler parameters of testicular blood flow, and semen parameters were obtained numerous times from this pony over four consecutive years. While testicular volume decreased dramatically, and the stallion became azoospermic, there were no changes in any of the spectral Doppler parameters of testicular blood f...
Laparoscopic Inguinal Hernioplasty with a Polyether Ether Ketone Anchoring Device in Intact Male Horses Does Not Compromise Testicular Perfusion, Sperm Production or Motility Characteristics.
Animals : an open access journal from MDPI    January 31, 2025   Volume 15, Issue 3 doi: 10.3390/ani15030402
Vitoria A, Barrachina L, Romero A, Fuente S, de Blas I, Gil L, Vázquez FJ.A new surgical technique using a polyether ether ketone (PEEK) anchoring device for testicle-sparing laparoscopic inguinal hernioplasty in stallions was described in 2023 and is known as the PEEK harpoon technique (PHT). In breeding stallions, it is essential that the surgery is effective in preventing inguinal hernia but also that it does not impair the testicular function. This study aims to evaluate whether the PHT may affect testicular function. To achieve that, changes in the testicular blood flow, sperm production and motility characteristics were assessed 28 days after use of the PHT. S...
Complications associated with equine transvaginal ultrasound-guided follicle aspiration: Practitioner survey and field results.
Journal of equine veterinary science    January 27, 2025   Volume 146 105363 doi: 10.1016/j.jevs.2025.105363
Hinrichs K, Schnobrich M, Fernandes CB, Fleury P, Barillari V, Bruggeworth S.Transvaginal ultrasound-guided follicle aspiration (TVA) is being performed commonly in clinical equine practice. There is limited information in the literature about the type and incidence of complications related to TVA. We conducted a survey (Study 1), completed by 23 practicing veterinarians, soliciting information about the types and incidence of minor and major complications and of fatalities they had experienced associated with performance of TVA. In Study 2, data from a large clinical practice in which six veterinarians performed over 14,000 TVAs over a period of 7 years was reviewed t...
Ultrasound-guided celiac plexus block increases intestinal motility in normal horses.
American journal of veterinary research    January 21, 2025   1-11 doi: 10.2460/ajvr.24.11.0328
Delvescovo B, Chevalier JM, Campoy L, Cercone M.To describe a technique for ultrasound-guided celiac plexus block in horses and characterize its effect on intestinal motility in healthy horses. Methods: This study was conducted from January 2022 through June 2022. In phase 1 (dye study), an ultrasound-guided technique was optimized, and dye deposition around the celiac plexus branches was evaluated via postmortem dissection in 6 horses. In phase 2 (experimental study), 6 healthy horses were fasted and sedated with 0.6 mg/kg xylazine, IV (experiment 1). After a washout period, the ultrasound-guided celiac plexus block with lidocaine 1% (1.3 ...
Anti-Müllerian hormone levels in relation to ovarian structures, season and age in Lipizzaner broodmares.
Acta veterinaria Hungarica    January 21, 2025   Volume 73, Issue 1 36-42 doi: 10.1556/004.2024.01131
Angyal E, Vincze B, Somoskői B, Sós-Koroknai V, Balogh P, Dankó GN, Cseh S, Kútvölgyi G.The anti-Müllerian hormone (AMH) is a granulosa cell-derived hormone that has been associated with female fertility and reflects the population of growing follicles. This study aimed to evaluate the average concentration of AMH in Lipizzaner mares, as well as to determine the relationship between AMH concentration and follicle number and size. We also investigated the relationship between the age of mares and their AMH levels. The possible effect of seasonality of AMH levels was also assessed. Twenty-three mares between 6 and 24 years of age were included in the experiment. Mares were divided...
A genome-wide association study for recurrent laryngeal neuropathy in the Thoroughbred horse identifies a candidate gene that regulates myelin structure.
Equine veterinary journal    January 10, 2025   doi: 10.1111/evj.14461
McGivney CL, McGivney BA, Farries G, Gough KF, Han H, Holtby AR, MacHugh DE, Katz LM, Hill EW.Equine recurrent laryngeal neuropathy (RLN) is an economically important upper respiratory tract (URT) disease with a genetic contribution to risk, but genetic variants independent of height have not been identified for Thoroughbreds. The method of clinical assessment for RLN is critical to accurately phenotype groups for genetic studies. Objective: To identify genetic risk loci for RLN in Thoroughbreds in a genome-wide association study (GWAS) following high-resolution phenotyping. Methods: Case-control. Methods: Thoroughbred horses were characterised as RLN cases and controls using resting a...
Abdominal Ultrasonography in Healthy Female Standard Donkeys.
Animals : an open access journal from MDPI    January 8, 2025   Volume 15, Issue 2 129 doi: 10.3390/ani15020129
Accorroni L, Bazzano M, Marchegiani A, Spaterna A, Laus F.Knowledge of the normal ultrasound anatomy in the donkey is essential to understand pathological changes and to reach an early diagnosis, considering the "dullness" and stoicism of these animals in pain manifestations. The aims of this study were to document which abdominal viscera could be identified using a transcutaneous ultrasonography technique under field conditions in unsedated, standing donkeys to determine where the different abdominal structures could be easily displayed and to describe any variation that occurred between different donkeys and horses. In this work, the manual techniq...
Real-time transrectal ultrasonographic measurement of the fetal eye (vitreous body) to predict parturition in bucking horse mares.
Journal of equine veterinary science    January 3, 2025   Volume 145 105345 doi: 10.1016/j.jevs.2025.105345
Gonzalez SW, Espy BMK, Stefanovski D, Turner RM.Monitoring gestation and predicting parturition in mares with unknown breeding dates is challenging, especially in pasture bred herds of bucking horses. Transrectal ultrasonographic measurement of fetal vitreous body length is a validated predictor of foaling dates, but previous research suggested a need for breed-specific parameters to develop accurate indices for respective breeds. This study aimed to develop a scale associating fetal vitreous body length with days before parturition (DBP) in bucking horses. Biannual data collection over 2 years identified 199 pregnancies out of 240 reproduc...
Plasma Cardiac Troponin-I Concentration in Normal Horses and in Horses with Cardiac Abnormalities.
Animals : an open access journal from MDPI    January 3, 2025   Volume 15, Issue 1 doi: 10.3390/ani15010092
Foreman JH, Tennent-Brown BS, Oyama MA, Sisson DD.Cardiac troponin-I (cTnI) is a highly sensitive and specific marker of myocardial injury detectable in plasma by immunoassay techniques. Inclusion criteria over a 3-year period required a diagnosis of cardiac disease accompanied by electrocardiographic (ECG) and cardiac ultrasound examinations (n = 23) in adult horses (≥2 years of age). A second group of normal adult ponies (n = 12) was studied as a reference group. Heparinized jugular venous blood samples were collected and centrifuged within 30 min, and the plasma was separated and frozen at -70 °C for subsequent batched cTnI analysis. Th...
Factors influencing oocyte recovery during ultrasound-guided follicle aspiration in mares: A postmortem study.
Theriogenology    December 31, 2024   Volume 235 39-45 doi: 10.1016/j.theriogenology.2024.12.032
Márquez-Moya A, Sala-Ayala L, Carreras-Vico N, Martínez-Boví R, Cuervo-Arango J.The objectives of this study were to investigate the influence of different OPU variables (vacuum and injection pressures during follicle aspiration and flushing, needle twisting to scrape follicles, number of follicle flushes and type of flushing media) on oocyte recovery rate (ORR) and morphology. Overall, 120 postmortem excised ovaries were processed in 62 replicates (1.9 ± 0.7 ovaries per replicate), with a total of 1336 follicles punctured and aspirated (11.1 ± 6.2 follicles per ovary) by ultrasound-guided follicle aspiration resembling the OPU procedure from live mares. The aspirat...
Development of an ultrasound-guided proximo-medial approach for injection of the carpal flexor tendon sheath in horses and comparison with the conventional proximo-lateral ´blind` technique.
Journal of equine veterinary science    December 20, 2024   105258 doi: 10.1016/j.jevs.2024.105258
Dörner CA, Vargas V, Castellón CH.The aim of this prospective case-control study was to describe and implement a reliable, accurate, and straightforward ultrasound-guided proximo-medial approach technique for injecting the carpal flexor tendon sheath in horses. The proximo-medial ultrasound-guided approach for intrathecal access to the carpal canal, as described in this study, was firstly developed on ten cadaveric limbs using an undiluted ionic iodinated contrast medium. Landmarks were identified, and the access point was established. Subsequently, the technique was validated in ten horses, and its efficacy was compared with ...
Birth of a Healthy Monozygotic Twin Foal with Hydrops and a Dead Co-Twin.
Veterinary sciences    December 13, 2024   Volume 11, Issue 12 649 doi: 10.3390/vetsci11120649
Peere S, Van den Branden E, Broothaers K, Polfliet E, Smits K, Govaere J.Transfer of in vitro-produced (IVP) equine embryos is associated with a higher incidence of monozygotic multiple pregnancies, but this remains a rarity. The outcome of monozygotic twin gestation is poor, and good management techniques are lacking. In addition, hydrops conditions are exceptional in horses, with hydroallantois occurring more frequently than hydramnion. Most hydrops conditions will lead to compromise or death of the foal and mare. A 6-year-old multiparous standardbred recipient mare, 332 days pregnant, diagnosed with a monozygotic twin and hydrops with a dead co-twin, gave birth ...
[Uroperitoneum in neonatal foals – Investigation on incidence, symptoms, laboratory findings and prognosis].
Tierarztliche Praxis. Ausgabe G, Grosstiere/Nutztiere    December 5, 2024   Volume 52, Issue 6 318-326 doi: 10.1055/a-2450-9437
Bernick A, Wehrend A.Uroperitoneum is a typical disease in newborn foals. It occurs rarely but regularly. The aim of the present study is to present clinical signs, laboratory findings and prognosis of foals with uroperitoneum. Methods: Medical records of 33 foals suffering from uroperitoneum that were treated between 2006 and June 2018 were reviewed retrospectively. Results: The incidence was 2.3% based of all presented foals during the first 14 days of life in the investigation period. Colts (78.8%) were significant more often affected (p=0,012) than fillies (21.2%). Common clinical signs were disturbed general ...
Decreased Circulating Red Cell Mass Induced by Intravenous Acepromazine Administration Alters Viscoelastic and Traditional Plasma Coagulation Testing Results in Healthy Horses.
Animals : an open access journal from MDPI    October 28, 2024   Volume 14, Issue 21 3102 doi: 10.3390/ani14213102
Mersich I, Bishop RC, Diaz Yucupicio S, Nobrega AD, Austin SM, Barger AM, Fick ME, Wilkins PA.Coagulopathy is common in equine critical illness, with its early recognition being crucial for patient management and prognosis. In vitro viscoelastic (VE) hypercoagulability with decreased RCM/PCV has been demonstrated in dogs but not horses. Our objective was to evaluate the effects of acepromazine-induced (0.1 mg/kg IV) decreased RCM on VE and plasma coagulation parameters using a prospective interventional study of eight adult horses. Complete blood count (CBC), fibrinogen, prothrombin time (PT), partial thromboplastin time (PTT), packed cell volume (PCV), total solids (TS), and VCM Vet...
Advancements in equine ophthalmic imaging enhance understanding of ocular and orbital anatomy and disease in standing sedated horses.
Journal of the American Veterinary Medical Association    October 25, 2024   Volume 262, Issue S2 S47-S56 doi: 10.2460/javma.24.06.0376
McMullen RJ.To review data on the advances in equine ophthalmic imaging that have been made during the past 5 years and highlight advantages of using multiple imaging modalities to improve clinical observational skills and improve diagnostic accuracy. Methods: A literature review from 2019 through 2024 of equine ophthalmic digital photography, fundus photography, ocular and orbital ultrasonography (US), ultrasound biomicroscopy (UBM), confocal microscopy (CM), spectral domain optical coherence tomography (SD-OCT), radiography, CT, and MRI. Results: Digital photography remains the cornerstone of equine oph...
Urinary incontinence and sabulous cystitis in mares: report of five cases.
Brazilian journal of veterinary medicine    October 21, 2024   Volume 46 e005024 doi: 10.29374/2527-2179.bjvm005024
de Melo UP, Ferreira C.This report describes five cases of urinary incontinence in Quarter Horse mares associated with the development of sabulous cystitis. The animals in this study had a history of persistent urinary incontinence for eight months, with clinical signs of continuous dribbling urine during rest and movement. The initial treatment with antibiotics and anti-inflammatory drugs was ineffective. Clinical examination revealed severe scalding in the perineal region and on the medial aspect of the hind limbs, along with neurological signs such as ataxia, hind limb paresis, and diminished perineal reflexes. T...
Ultrasonographic assessment of equine metacarpal cartilage thickness is more accurate than computed tomographic arthrography. Hoey S, Fogarty U, McAllister H, Puggioni A, Cloak B, Richard H, Skelly C, Laverty S.Articular cartilage can be directly imaged using ultrasonography. The fetlock is a common site of osteochondrosis, with the sagittal ridge of the third metacarpal bone most commonly affected. In osteochondrosis, cartilage thickening may be an initial finding. This postmortem study investigated the ability of ultrasonography to accurately measure the dorsodistal articular cartilage of the third metacarpal bone in young horses, compared to computed tomographic arthrography (CTA) and histological measurements. A total of 33 metacarpophalangeal joints from 18 horses between the ages of 12 days and...
A novel method for equine embryo transfer from contaminated recipient mares into second healthy recipients for surviving embryos.
Journal of equine veterinary science    September 19, 2024   Volume 142 105200 doi: 10.1016/j.jevs.2024.105200
Derbala MK, Abu-Seida AM, El-Metwally AE, Asfour HAE.Embryo transfer (ET) is regarded as one of the reproductive methods for genetic improvement initiatives in the horse business. The current study aimed to increase the success rate of ET by re-flushing and re-transferring of embryos from contaminated recipient mares into second healthy recipients. The study involved 25 recipient mares that demonstrated embryonic vesicles inside intraluminal fluid (ILF) on ultrasound scanning 2 ± 0.5 days after ET. Seven recipient mares were left without re-flushing and re-transferring of embryos (control group) and 18 recipient mares (treated group) were subje...
Effect of intrafollicular administration of PGE2 or PGF2α in early estrus on ovulation, hemorrhagic anovulatory follicles formation, progesterone secretion and pregnancy outcome in the mare.
Theriogenology    September 16, 2024   Volume 230 157-164 doi: 10.1016/j.theriogenology.2024.09.015
Gaber JTH, Cuervo-Arango J, Plaza-Dávila M, Martínez-Boví R.This experiment was performed to evaluate whether intrafollicular treatment of PGE2 or PGF2α administered in early estrus would induce normal ovulation, progesterone production (Experiment 1) and pregnancy (Experiment 2). In Experiment 1, mares in estrus after 2 days of endometrial edema were injected in all largest dominant follicles (28-35 mm in diameter) with 0.5 mL of sterile water containing 500 μg PGE2 (n = 6), 125 μg PGF2α (n = 6) or placebo (n = 7) (Hour 0). Ultrasound examinations were performed daily, until ovulation or anovulation was detected, and daily blood samples ...