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Topic:Equine Diseases

Equine diseases encompass a wide range of health conditions that can affect horses, including infectious diseases, metabolic disorders, and genetic conditions. These diseases can impact the overall health, performance, and well-being of horses. Common equine diseases include equine influenza, equine herpesvirus, laminitis, and equine metabolic syndrome. Diagnosis and management of these diseases often require a combination of clinical evaluation, laboratory testing, and appropriate treatment strategies. This page gathers peer-reviewed research studies and scholarly articles that explore the etiology, pathophysiology, diagnosis, and treatment options for various equine diseases, providing valuable insights for veterinarians and researchers in the field.
Capacity for sliding between tendon fascicles decreases with ageing in injury prone equine tendons: a possible mechanism for age-related tendinopathy?
European cells & materials    January 8, 2013   Volume 25 48-60 doi: 10.22203/ecm.v025a04
Thorpe CT, Udeze CP, Birch HL, Clegg PD, Screen HR.Age-related tendinopathy is common in both humans and horses; the initiation and progression of which is similar between species. The majority of tendon injuries occur to high-strain energy storing tendons, such as the human Achilles tendon and equine superficial digital flexor (SDFT). By contrast, the low-strain positional human anterior tibialis tendon and equine common digital extensor (CDET) are rarely injured. It has previously been established that greater extension occurs at the fascicular interface in the SDFT than in the CDET; this may facilitate the large strains experienced during l...
Passive transfer and rate of decay of maternal antibody against African horse sickness virus in South African Thoroughbred foals.
Equine veterinary journal    January 7, 2013   Volume 45, Issue 5 604-607 doi: 10.1111/evj.12015
Crafford JE, Lourens CW, Gardner IA, Maclachlan NJ, Guthrie AJ.African horse sickness is an insect-transmitted, noncontagious disease of equids caused by African horse sickness virus (AHSV). Mortality can exceed 90% in fully susceptible horse populations. A live-attenuated (modified live) cell-culture-adapted (MLV) polyvalent AHSV vaccine is widely used to control African horse sickness in endemic areas in southern Africa. Field studies detailing antibody responses of vaccinated horses are lacking. Objective: To determine antibody titres to the 9 known serotypes of AHSV in a cohort of broodmares that were regularly vaccinated with the MLV AHSV vaccine and...
The accuracy of the National Equine Database in relation to vector-borne disease risk modelling of horses in Great Britain.
Equine veterinary journal    January 7, 2013   Volume 45, Issue 3 302-308 doi: 10.1111/evj.12018
Robin CA, Lo Iacono G, Gubbins S, Wood JL, Newton JR.The National Equine Database (NED) contains information on the size and distribution of the horse population, but the data quality remains unknown. These data could assist with surveillance, research and contingency planning for equine infectious disease outbreaks. Objective: 1) To assess the extent of obsolete and missing data from NED, 2) evaluate the extent of spatial separation between horse and owner location and 3) identify relationships between spatial separation and land use. Methods: Two questionnaires were used to assess data accuracy in NED utilising local authority passport inspect...
Characteristics of palatal instability in Thoroughbred racehorses and their association with the development of dorsal displacement of the soft palate.
Equine veterinary journal    January 7, 2013   Volume 45, Issue 4 454-459 doi: 10.1111/evj.12004
Allen K, Franklin S.Two forms of dynamic upper respiratory tract obstruction affecting racehorses that involve the soft palate have been described: palatal instability (PI) and dorsal displacement of the soft palate (DDSP). Observation of DDSP is straightforward in that it is an all or nothing event, whereas observation of PI is subjective and interpretation may vary between clinicians. Objective: The aim of this study was to attempt to characterise PI and to investigate endoscopic features that precede DDSP. Methods: A retrospective study on the endoscopic observations of Thoroughbred racehorses referred for hig...
Reliability of 400-cell and 5-field leukocyte differential counts for equine bronchoalveolar lavage fluid.
Veterinary clinical pathology    January 3, 2013   Volume 42, Issue 1 92-98 doi: 10.1111/vcp.12013
Fernandez NJ, Hecker KG, Gilroy CV, Warren AL, Léguillette R.Reliable enumeration of mast cells and eosinophils in equine bronchoalveolar lavage (BAL) fluid is important because small increases in the percentages of these cells support the clinical diagnosis of inflammatory airway disease (IAD). Increases in BAL neutrophils also occur with IAD but are not specific due to overlap between IAD and recurrent airway obstruction (RAO). Objective: The objectives of this study were to evaluate the reliability of a standard 400-cell leukocyte differential count and an alternate method evaluating 5 microscopic fields at 500× magnification in equine BAL fluid cyt...
Immunogenomic analysis of insect bite hypersensitivity in a model horse population.
Veterinary immunology and immunopathology    January 3, 2013   Volume 152, Issue 3-4 260-268 doi: 10.1016/j.vetimm.2012.12.013
Vychodilova L, Matiasovic J, Bobrova O, Futas J, Klumplerova M, Stejskalova K, Cvanova M, Janova E, Osickova J, Vyskocil M, Sedlinska M, Dusek L....Equine insect bite hypersensitivity (IBH) is a seasonal IgE-mediated dermatosis caused by bites of insects of the genus Culicoides. A familial predisposition for the disease has been shown but, except for the MHC, the genes involved have not been identified so far. An immunogenomic analysis of IBH was performed in a model population of Old Kladruby horses, all living in the same environment. Clinical signs of IBH were used as phenotypic manifestation of IBH. Furthermore, total serum IgE levels were determined in the sera of these horses and used as an independent phenotypic marker for the immu...
Hydrocortisone inhibits IFN-γ production in equine, ovine, and bovine PBMCs.
Veterinary immunology and immunopathology    January 3, 2013   Volume 153, Issue 1-2 128-133 doi: 10.1016/j.vetimm.2012.12.012
McCandless EE, Rai SK, Mwangi D, Sly L, Franz LC.Hydrocortisone is widely accepted as an anti-inflammatory agent and there are many products available containing hydrocortisone as an active ingredient. Surprisingly, there is little data available specifically on the immunological effects of hydrocortisone in large animals. Glucocorticoids are well-characterized for their ability to repress inflammation via a wide variety of mechanisms including suppression of cytokine production. In this study the effects of hydrocortisone on IFN-γ production by equine, bovine, and ovine PBMCs were assessed using flow cytometric or ELISpot analysis. Hydroco...
Ultrasonographic features of PMEL17 (Silver) mutant gene-associated multiple congenital ocular anomalies (MCOA) in Comtois and Rocky Mountain horses.
Veterinary ophthalmology    January 1, 2013   Volume 16, Issue 6 429-435 doi: 10.1111/vop.12021
Ségard EM, Depecker MC, Lang J, Gemperli A, Cadoré JL.(1) To describe the ultrasonographic appearance of multiple congenital ocular anomalies (MCOA) in the eyes of horses with the PMEL17 (Silver) mutant gene. (2) To compare the accuracy of B-mode ocular ultrasound to conventional direct ophthalmoscopy. Methods: Sixty-seven Comtois and 18 Rocky Mountain horses were included in the study. Methods: Horses were classified as being carriers or noncarriers of the PMEL17 mutant allele based on coat color or genetic testing. Direct ophthalmoscopy followed by standardized ultrasonographic examination was performed in all horses. Results: Seventy-five of 8...
Therapeutic effect of adipose-derived mesenchymal stem cell injection in horses suffering from bone spavin.
Polish journal of veterinary sciences    January 1, 2013   Volume 16, Issue 4 753-754 doi: 10.2478/pjvs-2013-0107
Nicpoń J, Marycz K, Grzesiak J.In this article we demonstrate the efficiency of autologous transplantations of adipose-derived mesenchymal stem cells for equine bone spavin treatment. Horses qualified to the study were divided into three groups: (i) research - treated with intra-articular injections of autologous stem cells, (ii) comparison treated with steroid drugs and (iii) control - untreated. All animals underwent comprehensive clinical examination before and after treatment. Our research confirms the long-term beneficial influence resulting from stem cell therapy in horse bone spavin treatment, in contrast to routine ...
Magnetic resonance protocols in equine lameness examination, used sequences, and interpretation.
Polish journal of veterinary sciences    January 1, 2013   Volume 16, Issue 4 803-811 doi: 10.2478/pjvs-2013-0115
Jaskólska M, Adamiak Z, Zhalniarovich Y, Holak P, Przyborowska P.Magnetic resonance is a great diagnostic tool in equine lameness examination. Its value is most significantly visible in evaluating distal extremities. Problems with podotrochlear apparatus, laminitis or distal interphalangeal joint osteoarthritis are the most common disorders diagnosed in equine patients. Without using magnetic resonance it was impossible to clearly assess which structures are involved in each of these diseases. One of the most important things in MRI is the choice of sequence. Most commonly used are T1 GE, T2 FSE, STIR and T2* GE, in sagittal, transverse and dorsal planes. T...
The first investigation of west nile virus in horses using real time rt-PCR in middle black sea region in Turkey.
Journal of arthropod-borne diseases    December 31, 2012   Volume 6, Issue 2 151-155 
Yazici Z, Albayrak H, Ozan E, Gumusova S.West Nile Virus (WNV) is a mosquito-borne disease that can cause fatal infection in mammals including humans, dogs, horses, birds and reptiles. Although West Nile Virus is an asymptomatic infection, especially it can cause neurologic disorders in humans and horses. The aim of this study was to the investigate virological presence of WNV in horses in the Black Sea Region of Turkey using real time RT-PCR (rRT-PCR). Methods: Totally, 120 horse sera were collected equally from 4 provinces in Middle Black Sea Region of Turkey and investigated for WNV presence by Taqman based rRT-PCR. Results: WNV n...
Serum biochemical reference intervals for the Polish Konik horse (Equus cabalus gmelini Ant.).
Veterinary clinical pathology    December 31, 2012   Volume 42, Issue 1 66-69 doi: 10.1111/vcp.12020
Niedźwiedź A, Jaworski Z, Filipowski H, Zawadzki M, Wrzosek M, Służewska-Niedźwiedź M, Nicpoń J.Establishment of reference intervals (RI) for serum biochemical analytes is important for monitoring the health of different breeds of horses. Objective: The aim of this study was to measure and report RI for serum biochemical analytes of the Polish Konik horse. Methods: Blood samples were collected from 74 clinically healthy Polish Konik horses living under controlled natural conditions. These were adult primitive horses, aged 3-15 years, including 28 males (21 stallions, 7 geldings) and 46 mares. Serum analytes were measured and analyzed using a commercial automated analyzer. Results: The fo...
Development of a broad-range quantitative polymerase chain reaction assay to detect and identify fungal DNA in equine endometrial samples.
American journal of veterinary research    December 29, 2012   Volume 74, Issue 1 161-165 doi: 10.2460/ajvr.74.1.161
Ferris RA, Dern K, Veir JK, Hawley JR, Lappin MR, McCue PM.To develop a broad-range 28S ribosomal DNA quantitative PCR (qPCR) assay for detection of fungal DNA in equine endometrial samples. Methods: 12 fungal samples from a clinical diagnostic laboratory and 29 samples obtained from 17 mares. Methods: The qPCR assay was optimized with commercially acquired fungal organisms and validated with samples obtained from the clinical diagnostic laboratory. Subsequently, 29 samples from 17 mares suspected of having fungal endometritis were evaluated via the qPCR assay and via traditional fungal culture and endometrial cytology. Amplicons from the qPCR assay w...
Comparison of a body-mounted inertial sensor system-based method with subjective evaluation for detection of lameness in horses.
American journal of veterinary research    December 29, 2012   Volume 74, Issue 1 17-24 doi: 10.2460/ajvr.74.1.17
Keegan KG, Wilson DA, Kramer J, Reed SK, Yonezawa Y, Maki H, Pai PF, Lopes MA.To compare data obtained with an inertial sensor system with results of subjective lameness examinations performed by 3 experienced equine veterinarians for evaluation of lameness in horses. Methods: 106 horses. Methods: Horses were evaluated for lameness with a body-mounted inertial sensor system during trotting in a straight line and via subjective evaluation by 3 experienced equine practitioners who performed complete lameness examinations including lunging in a circle and limb flexion tests. Agreement among evaluators regarding results of subjective evaluations and correlations and agreeme...
Development of an in vitro model of injury-induced osteoarthritis in cartilage explants from adult horses through application of single-impact compressive overload.
American journal of veterinary research    December 29, 2012   Volume 74, Issue 1 40-47 doi: 10.2460/ajvr.74.1.40
Lee CM, Kisiday JD, McIlwraith CW, Grodzinsky AJ, Frisbie DD.To develop an in vitro model of cartilage injury in full-thickness equine cartilage specimens that can be used to simulate in vivo disease and evaluate treatment efficacy. Methods: 15 full-thickness cartilage explants from the trochlear ridges of the distal aspect of the femur from each of 6 adult horses that had died from reasons unrelated to the musculoskeletal system. Methods: To simulate injury, cartilage explants were subjected to single-impact uniaxial compression to 50%, 60%, 70%, or 80% strain at a rate of 100% strain/s. Other explants were left uninjured (control specimens). All speci...
Equine platelets inhibit E. coli growth and can be activated by bacterial lipopolysaccharide and lipoteichoic acid although superoxide anion production does not occur and platelet activation is not associated with enhanced production by neutrophils.
Veterinary immunology and immunopathology    December 28, 2012   Volume 152, Issue 3-4 209-217 doi: 10.1016/j.vetimm.2012.12.007
Aktan I, Dunkel B, Cunningham FM.Activated platelets can contribute to host defense through release of products with bactericidal actions such as antimicrobial peptides and reactive oxygen species (ROS), as well as by forming heterotypic aggregates with neutrophils and enhancing their antimicrobial properties. Whilst release of vasoactive mediators from equine platelets in response to stimuli including bacterial lipopolysaccharide (LPS) has been documented, neither ROS production, nor the effects of activated platelets on equine neutrophil ROS production, have been reported. This study first sought evidence that activated equ...
Controlling equine influenza: policy networks and decision-making during the 2007 Australian equine influenza outbreak.
Transboundary and emerging diseases    December 28, 2012   Volume 61, Issue 5 449-463 doi: 10.1111/tbed.12046
Schemann K, Gillespie JA, Toribio JA, Ward MP, Dhand NK.Rapid, evidence-based decision-making is critical during a disease outbreak response; however, compliance by stakeholders is necessary to ensure that such decisions are effective - especially if the response depends on voluntary action. This mixed method study evaluated technical policy decision-making processes during the 2007 outbreak of equine influenza in Australia by identifying and analysing the stakeholder network involved and the factors driving policy decision-making. The study started with a review of the outbreak literature and published policy documents. This identified six policy ...
Coadministration of sodium alginate pellets containing the fungi Duddingtonia flagrans and Monacrosporium thaumasium on cyathostomin infective larvae after passing through the gastrointestinal tract of horses.
Research in veterinary science    December 27, 2012   Volume 94, Issue 3 568-572 doi: 10.1016/j.rvsc.2012.11.011
Tavela Ade O, de Araújo JV, Braga FR, da Silveira WF, Dornelas e Silva VH, Carretta Júnior M, Borges LA, Araujo JM, Benjamin Ldos A, Carvalho GR....The predatory nematophagous fungi have been used as an alternative control of gastrointestinal nematodes of domestic animals in natural and laboratory conditions. However, it is unclear if the association of some of these species could bring some kind of advantage, from a biological standpoint. In this context, this study consisted of two tests in vitro: in assay A, the assessment of the viability of the association of pellets in sodium alginate matrix containing the fungus Duddingtonia flagrans (AC001) and Monacrosporium thaumasium (NF34) and its predatory activity on infective larvae (L3) of...
Contagious equine metritis: artificial reproduction changes the epidemiologic paradigm.
Veterinary microbiology    December 26, 2012   Volume 167, Issue 1-2 2-8 doi: 10.1016/j.vetmic.2012.12.021
Schulman ML, May CE, Keys B, Guthrie AJ.Recent CEM outbreak reports reflect a novel epidemiologic manifestation with a markedly different risk association for transmission via artificial reproduction and subsequent to inadvertent importation of unapparent carrier stallions. Artificial breeding has an increased association with horizontal or fomite-associated transmission. Reported risk factors include inadequate biosecurity protocols at centralised breeding facilities associated with stallion management and methods of semen collection, processing and transport. Detection of carriers is based on traditional bacteriology from genital ...
Expression of fluorescent reporter protein in equine embryos produced through intracytoplasmic sperm injection mediated gene transfer (ICSI-MGT).
Animal reproduction science    December 26, 2012   Volume 137, Issue 1-2 53-61 doi: 10.1016/j.anireprosci.2012.12.010
Zaniboni A, Merlo B, Zannoni A, Bernardini C, Lavitrano M, Forni M, Mari G, Bacci ML.Sperm mediated gene transfer (SMGT) has been reported to be a powerful tool for producing transgenic livestock with applications in biomedicine and agriculture. To date, two studies have reported the production of transgenic equine embryo with, however, low efficiency in blastocyst production and transgene expression. The aim of the present study was to develop a method which allowed the efficient production of transgene-expressing embryos of the equine species through SMGT. To overcome problems due to in vitro fertilization (IVF) in horses, the ICSI procedure was associated with SMGT. The upt...
Improving the diagnosis of equine colic.
The Veterinary record    December 25, 2012   Volume 171, Issue 25 636 doi: 10.1136/vr.e8562
No abstract available
Genome-wide association study of osteochondrosis in the tarsocrural joint of Dutch Warmblood horses identifies susceptibility loci on chromosomes 3 and 10.
Animal genetics    December 25, 2012   Volume 44, Issue 4 408-412 doi: 10.1111/age.12016
Orr N, Hill EW, Gu J, Govindarajan P, Conroy J, van Grevenhof EM, Ducro BJ, van Arendonk JA, Knaap JH, van Weeren PR, Machugh DE, Ennis S, Brama PA.Equine osteochondrosis is a developmental joint disease that is a significant source of morbidity affecting multiple breeds of horse. The genetic variants underlying osteochondrosis susceptibility have not been established. Here, we describe the results of a genome-wide association study of osteochondrosis using 90 cases and 111 controls from a population of Dutch Warmblood horses. We report putative associations between osteochondrosis and loci on chromosome 3 (BIEC2-808543; P = 5.03 × 10(-7) ) and chromosome 10 (BIEC2-121323; P = 2.62 × 10(-7) ).
A novel strategy of mesenchymal stem cells delivery in the uterus of mares with endometrosis.
Theriogenology    December 25, 2012   Volume 79, Issue 5 744-750 doi: 10.1016/j.theriogenology.2012.11.030
Mambelli LI, Winter GH, Kerkis A, Malschitzky E, Mattos RC, Kerkis I.Mesenchymal stem cells (MSCs), because of their immunomodulation and trophic activities, in addition to their capacity to regenerate damaged tissues, have potential for treatment of many diseases. The success of stem cell therapies depends, in part, on the method of cell delivery, which should provide wide cell distribution and homing in to injured sites. The objective of the present study was to developing a novel strategy for delivery of MSCs into the uterus of mares with endometrosis (degenerative alteration of uterine glands and surrounding stroma). Endometrosis was confirmed in all mares ...
Balanced anesthesia and constant-rate infusions in horses.
The Veterinary clinics of North America. Equine practice    December 23, 2012   Volume 29, Issue 1 89-122 doi: 10.1016/j.cveq.2012.11.004
Valverde A.Balanced anesthetic techniques are commonly used in equine patients, and include the combination of a volatile anesthetic with at least one injectable anesthetic throughout the maintenance period. Injectable anesthetics used in balanced anesthesia include the α2-agonists, lidocaine, ketamine, and opioids, and those with muscle-relaxant properties such as benzodiazepines and guaifenesin. Administration of these injectable anesthetics is best using constant-rate infusions based on the pharmacokinetics of the drug, which allows steady-state concentrations and predictable pharmacodynamic actions....
Effect of myeloperoxidase and anoxia/reoxygenation on mitochondrial respiratory function of cultured primary equine skeletal myoblasts.
Mitochondrion    December 22, 2012   Volume 13, Issue 5 410-416 doi: 10.1016/j.mito.2012.12.004
Ceusters JD, Mouithys-Mickalad AA, Franck TJ, Derochette S, Vanderplasschen A, Deby-Dupont GP, Serteyn DA.Horses are particularly sensitive to excessive inflammatory reaction where myeloperoxidase, a marker of inflammation, may contribute to mitochondrial dysfunctions. This study investigated the interaction between myeloperoxidase and cultured primary equine skeletal myoblasts, particularly its effect on mitochondrial respiration combined or not with anoxia followed by reoxygenation (AR). We showed that active myeloperoxidase entered into the cells, interacted with mitochondria and decreased routine and maximal respirations. When combined with AR, myeloperoxidase caused a further decrease of thes...
Ovarian response to porcine FSH in association with ablation-induced or spontaneous follicular wave development during the estrous cycle in crossbred and Brazilian Warmblood mares.
Animal reproduction science    December 20, 2012   Volume 137, Issue 1-2 82-87 doi: 10.1016/j.anireprosci.2012.12.003
Ignácio FS, Bergfelt DR, Mendes D, Orlandi C, Araújo GH, Oliveira JV, Montechiesi DF, Carvalho LR, Meira C.The primary objective of this study was to examine the follicular and ovulatory responses following treatment with pFSH in association with ablation-induced or spontaneous follicular wave emergence or follicle deviation during diestrus in crossbred (Mangalarga×Arabian) and Brazilian Warmblood mares with a propensity for spontaneous multiple ovulations; secondary considerations were given to the collection of embryos. In Experiment 1, crossbred mares were administered (im) saline (control, n=7) or pFSH (25mg) when the largest follicle of the ablation-induced follicular wave reached ≥13mm (n=...
Lidocaine and structure-related mexiletine induce similar contractility-enhancing effects in ischaemia-reperfusion injured equine intestinal smooth muscle in vitro.
Veterinary journal (London, England : 1997)    December 20, 2012   Volume 196, Issue 3 461-466 doi: 10.1016/j.tvjl.2012.11.011
Tappenbeck K, Hoppe S, Hopster K, Kietzmann M, Feige K, Huber K.Postoperative ileus (POI) is a severe complication following small intestinal surgery in horses. It was hypothesised that prokinetic effects of lidocaine, the most commonly chosen drug for treatment of POI, resulted from drug integration into smooth muscle (SM) cell membranes, thereby modulating cell membrane properties. This would probably depend on the structural and lipophilic characteristics of lidocaine. To assess the influence of molecular structure and lipophilicity on prokinetic effects in vitro, the current study compared the effects of lidocaine with four structure-related drugs, nam...
Diagnosis of dourine in outbreaks in Italy.
Veterinary parasitology    December 20, 2012   Volume 193, Issue 1-3 30-38 doi: 10.1016/j.vetpar.2012.12.006
Pascucci I, Di Provvido A, Cammà C, Di Francesco G, Calistri P, Tittarelli M, Ferri N, Scacchia M, Caporale V.Dourine is trypanosomosis that affects equids, it's mainly sexually transmitted. The disease was first eradicated in Italy in the 1940s, but there was then a serious epidemic in the mid-70s. After sporadic reports at the end of the 1990s, in May 2011 it was reported once more. Clinical diagnosis of dourine can be complex, as clinical signs and gross lesions are not always present. Direct laboratory diagnosis is also problematic, given the low number of parasites normally present in infected tissues and the mild, short-lasting parasitaemia. This article describes the epidemiological, clinical a...
Genome-wide association study implicates testis-sperm specific FKBP6 as a susceptibility locus for impaired acrosome reaction in stallions.
PLoS genetics    December 20, 2012   Volume 8, Issue 12 e1003139 doi: 10.1371/journal.pgen.1003139
Raudsepp T, McCue ME, Das PJ, Dobson L, Vishnoi M, Fritz KL, Schaefer R, Rendahl AK, Derr JN, Love CC, Varner DD, Chowdhary BP.Impaired acrosomal reaction (IAR) of sperm causes male subfertility in humans and animals. Despite compelling evidence about the genetic control over acrosome biogenesis and function, the genomics of IAR is as yet poorly understood, providing no molecular tools for diagnostics. Here we conducted Equine SNP50 Beadchip genotyping and GWAS using 7 IAR-affected and 37 control Thoroughbred stallions. A significant (PA and g.11040379C>A (p.166H>N) in exon 4 that were significantly associated with the IAR phenotype both in the GWAS cohort (n = 44) and in a large multi-breed cohort of 265 ho...
Quantification, morphology, and viability of equine preantral follicles obtained via the Biopsy Pick-Up method.
Theriogenology    December 20, 2012   Volume 79, Issue 4 599-609 doi: 10.1016/j.theriogenology.2012.11.012
Haag KT, Magalhães-Padilha DM, Fonseca GR, Wischral A, Gastal MO, King SS, Jones KL, Figueiredo JR, Gastal EL.A Biopsy Pick-Up (BPU) method was tested to determine the feasibility of retrieving preantral follicles from mare ovaries in vivo. A total of 33 ovarian biopsy procedures were performed on 18 mares during the breeding season. Mares were 5 to 21 years old and biopsies were performed during the estrous and/or diestrous phase, as confirmed by transrectal ultrasonography. Follicles were mechanically isolated using a tissue chopper, counted, and classified as normal or abnormal and primordial or primary. Viability of isolated follicles was determined by Trypan Blue dye. A total of 256 biopsy attemp...