The testes in horses are reproductive organs responsible for the production of sperm and the secretion of hormones such as testosterone. Located in the scrotum, the testes play a vital role in male fertility and reproductive behavior. They consist of seminiferous tubules where spermatogenesis occurs, and interstitial cells, also known as Leydig cells, which produce testosterone. The function and health of equine testes can be influenced by factors such as age, season, and overall health status. This page compiles peer-reviewed research studies and scholarly articles that explore the anatomy, physiology, and pathology of the testes in horses, providing insights into their role in equine reproduction and breeding management.
DAVIES J, DEMPSEY EW, WISLOCKI GB.A fetal horse ovary at the 6th month of gestation and a fetal ovary and testis at the 9th month have been studied histochemically with special reference to the cytoplasmic lipids of the interstitial cells. At least two lipid fractions appeared to be present, one which was soluble in acetone and was mainly responsible for the positive "plasmal" reaction, and another, insoluble in acetone, which was responsible for the sudanophilic, Ashbel-Seligman and periodic acid-Schiff positive material remaining after acetone extraction. The interstitial cell lipids in the older ovary and testis were also a...
Serum anti-Müllerian hormone (AMH), a marker of equine cryptorchidism, is detectable in intact and cryptorchid stallions but not in geldings because it is secreted from Sertoli cells. A 4-year-old uncastrated Thoroughbred racehorse had no visible testes; therefore, the horse was considered a bilateral cryptorchidism. However, the serum AMH was undetectable (<0.08 ng/ml). Human chorionic gonadotrophin (hCG) stimulating test result indicated that the horse was a gelding. The results of sex chromosomal analysis and sequence analysis of SRY gene suggested that the horse was a genetically-intac...
Merchant-Larios H.The establishment and sexual differentiation of the gonads of horse embryos were studied using high-resolution techniques. The most dramatic observation is the early cytodifferentiation of the somatic cells into steroidogenic cells which takes place before sexual differentiation of the gonads. A unique morphogenetic pattern is established during this process: the seminiferous cords of the testis are completely segregated from the steroidogenic tissue by a basal lamina, while in the medulla of the ovary, steroidogenic cells differentiate inside the epithelial cords which contain germ cells. Thi...
al-Bagdadi F, Hoyt P, Karns P, Martin G, Memon M, McClure R, McCoy D, Shoemaker S.Eleven unilateral cryptorchid stallions, two to three years old, were castrated at Louisiana State University Veterinary Teaching Hospital. Five of these cryptorchid cases were abdominal and the rest were inguinal. This study was initiated to document the differences between the abdominal and inguinal equine cryptorchid testes. Specimens were obtained from the abepididymal side of each cryptorchid testes and processed for light and electron microscopic study. The cryptorchid testes were smaller than the scrotal testes, with the abdominal testes being one-fourth the size of the scrotal testes. ...
Araujo JF, Righini AS, Fleury JJ, Caldas MC, Costa-Neto JB, Marques N.An attempt has been made to define semen seasonality in a horse in the Southern Hemisphere. Repeated measurements of three variables in the semen were made for 36 months (Jan/90-Dec/92) in a 21-year old "Mangalarga" stallion living under natural photoperiod and temperature conditions in a farm situated in São José do Rio Pardo, São Paulo, Brazil (latitude 21 degrees) 36'S; longitude 46 degrees 53' W). The horse fed on natural pasture and a nutritionally balanced feed twice a day (11:00 and 17:00 h). Water and mineral supplement were available ad libitum. Semen was collected almost daily by ...
Braun J, Muto Y, Sato K, Schallenberger E.Semen from three stallions was collected weekly for six months (December through May) to determine semen parameters and hormones (testosterone and estradiol-17 beta) in seminal plasma. Once a month three ejaculates were collected at intervals of one hour and examined accordingly. Testosterone and estradiol-17 beta were also determined in peripheral blood plasma (V. jugularis) collected twice a week. Semen parameters (volume, gel-free volume and sperm concentration) were clearly influenced by season. The testosterone concentration in peripheral blood plasma was lowest during December whereas in...
Stumpf G, Fietz D, Ezer J, Litzke LF, Bergmann M.Surgically removed testicular tissue in cryptorchid stallions is sometimes difficult to identify because of morphological and histological malformation. Therefore, a sure method to characterise the removed tissue is required. A 2-year-old Haflinger stallion was castrated after diagnosis of cryptorchidism to remove the left intra-abdomnial testis. Intra-operative exploration of the abdominal cavity revealed a firm, dysmorphic structure, which could not be identified as testis based on macroscopic anatomy. The removed tissue was Bouin-fixed and paraffin-embedded for histological examination. We ...
Kenney RM, Cummings MR, Teuscher C, Love CC.Testicular degeneration is a major cause of subfertility in stallions, although an aetiological diagnosis cannot be made in most cases. In the present study, autoimmune testicular degeneration was induced and evaluated in stallions by immunizing stallions with their own spermatozoa mixed with an adjuvant. The factors evaluated included changes in semen quality and testicular histology. A large decrease in sperm number and quality was observed in response to sperm autoantigens. An ELISA test specific for antisperm antibodies was developed which enabled antibody titres in serum, seminal plasma a...
Serafini R, Varner DD, Love CC.Flow cytometry procedures can be used for evaluation of both spermatogenic efficiency and diagnose disorders of stallion spermatogenesis. Aims of this study were to compare two testicular sample acquisition techniques (needle aspirate-N and tissue wedge-T) and results when using flow cytometry and histology procedures. Testicular cell types were stained with acridine orange, and nine regions (R2 to R10) were identified and enumerated following acquisition by either N or T. Testes were also grouped and analyzed by size and sexual maturity (Small [immature] compared with Large [mature]) and used...
De Botton D, Janett F, Burger D, Imboden I, Kähn W, Thun R.The aim of the present study was to investigate the spermatogenic and Leydig cell activity in stallions with impaired semen quality after treatment with equine somatotropin. Experiments were performed using 18 adult clinically healthy stallions with poor semen quality which did not pass breeding soundness evaluation. The animals were randomly divided into a treatment (n = 9) and a control (n = 9) group. Over a period of 90 days, nine stallions received a daily intramuscular injection of 10 mg recombinant equine somatotropin (EquiGen, BresaGen Limited, Adelaide, Australia) and 9 control animals...
Held JP, Prater P, Stettler M.A 9-year-old Arabian stallion with a 3-year history of infertility was evaluated for breeding soundness. Both testes were small. Ultrasonography revealed a small amount of free fluid between the tunics of both testes. Results of cytologic examination of the fluid were unremarkable. On semen examination, progressive motility was 10%, and total number of spermatozoa in the ejaculate was 6.6 x 10(9), of which 92% were abnormal. Predominant abnormalities were head defects (75%): 57% of the heads had single or multiple vacuoles, and 60% also had midpiece swelling or bending.
Berndtson WE, Jones LS.Testes were obtained from 47 1-20-year-old stallions during the natural breeding season. Total testicular testosterone and testosterone/g testis increased with age (P less than 0.005), and total testicular testosterone was associated with larger testis size (P less than 0.05). Neither testosterone per gram nor per paired testes were related to total Sertoli cell number (P greater than 0.05), but greater testosterone per paired testes was associated with fewer Sertoli cells per unit of seminiferous tubule length (P less than 0.005) or basement membrane area (P less than 0.02) and with a higher ...
Saifzadeh S, Hobbenaghi R, Asri-Rezaei S, Shokouhi S J F, Dalir-Naghadeh B, Rohi S M.A novel technique [Section-Ligation-Release (SLR)] was evaluated for castration in the horse. Clinical traits, serum testosterone concentrations after challenge with human chorionic gonadotrophin (hCG), and histopathological changes of the testicular tissue were assessed. Five stallions, aged 24-48 months, were castrated using SLR technique under general anaesthesia. Both spermatic cords in each stallion were exposed at the scrotal neck by two 5-cm long incisions, followed by sharp dissection through the parietal vaginal tunic. Both vascular and non-vascular structures in the cords were triple...
Oh R, Tamaoki BI.The microsomal fraction (10 000–105 000 × g precipitate) of equine testes was fractionated into the smooth- and the rough-surfaced microsomal subfractions by a sucrose density-gradient centrifugation in the presence of CsCl. The validity of this fractionating procedure was confirmed by electron microscopic examination and also by chemical analysis of the RNA contents in these subfractions. The aromatizing enzyme system (19-hydroxylase and aromatase) which was concentrated in the microsomal fractions among the organellae was found to be localized in the smoothsurfaced microsomal fraction. Th...
Hoshiba H, Sinowatz F.Spermadhesins are proteins with various functions in sperm capacitation and zona pellucida binding. In this study the cellular localization of the spermadhesin AWN-1 has been examined in the equine male genital tract. Results obtained by immunohistochemical methods reveal that in the horse AWN-1 is synthesized in spermatogonia, in the rete testis, the ductus epididymidis and the seminal vesicles. These findings indicate that the cellular origin of spermadhesins is species-specific.
Shakeel M, Choi Y, Yoon M.Cryptorchidism affects spermatogenesis and testis development, often resulting in stallion subfertility/infertility. This study aims to identify the specific germ cells impacted by cryptorchism in stallions. In a previous study, we found that PGP9.5 and VASA are molecular markers expressed in different germ cells within stallions. Herein, we assessed the heat stress-induced response of spermatogonial stem cells (SSCs) in the seminiferous tubules (ST) of cryptorchid stallion testes (CST) and normal stallion testes (NST). This goal was accomplished by comparing PGP9.5 and VASA expression pattern...
Johnson SA, Sikes KJ, Johnson JW, Van Zeeland E, Wist S, Santangelo KS, King MR, Frisbie DD.Low load exercise training with blood flow restriction (BFR) has become increasingly used by human physical therapists to prescribe controlled exercise following orthopaedic injury; its effects on the equine superficial digital flexor tendon (SDFT), however, are unknown. Objective: To investigate outcomes of pressure specific BFR walking exercise on uninjured equine SDFT biomechanics and histomorphology. Methods: Controlled in vivo experiment. Methods: Four forelimbs of four horses were exposed to 40 BFR-walk sessions (10-min interval walking) on a treadmill over a 56-day study period with the...
Yi M, Asgenbaatar N, Wang X, Ulaangerel T, Shen Y, Wen X, Du M, Dong X, Dugarjav M, Bou G.DNA methyltransferases (DNMTs) are important epigenetic modification during spermatogenesis. To further evaluate the pattern of DNMTs in horse testes during development, we investigated the expression and localization of DNMT1, DNMT3a and DNMT3b at different time points. The qRT-PCR results showed that DNMT1 expression was maintained in testes tissue from 6-month-old (0.5y) to 2-year-old (2y) of age and decreased after 3-year-old (3y) (P < 0.01). The expression levels of DNMT3a and DNMT3b peaked in testes tissue at 3y (P < 0.01). At 4-year-old (4y), the expression of DNMT3a and DNMT3b was ...
Asgenbaatar N, Yi M, Wang X, Ulaangerel T, Shen Y, Wen X, Du M, Dong X, Mengkh Y, Dugarjav M, Bou G.The preparation of paraffin sections is an important experimental technique in animal histological research, and key factors that determine the quality of a section include the dehydration time, waxing time, and drying temperature of the paraffin section. Paraffin sections obtained from testis tissue of adult horses exhibited higher quality with clear tissue structure and complete cell morphology after they underwent gradient dehydration for 6 hours, were immersed in wax for 60 minutes, and were dried in a 75-degree oven for 15 minutes. The detailed, optimized procedures that are developed in ...
Jung H, Yoon M.Spermatogonial stem cells originate from gonocytes and undergo self-renewal and differentiation to generate mature spermatozoa via spermatogenesis in the seminiferous tubules of the testis in male mammals. Owing to the unique capacity of these cells, the spermatogonial stem cell transplantation technique, which enables the restoration of male fertility by transfer of germlines between donor and recipient males, has been developed. Thus, spermatogonial stem cell transplantation can be used as an important next-generation reproductive and breeding tool in livestock production. However, in large ...
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...
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...
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...
Baatar T, Song D, Weng Y, Wang G, Jin L, Guo R, Li B, Dugarjaviin M.The epigenetic regulation of gene expression through the covalent modification of histones is crucial for developing germline cells. To study the regulatory role of alternative splicing (AS) of euchromatic histone lysine methyltransferase 2 (EHMT2/G9A) in spermatogenesis in Mongolian horses, this study first examines the localization of the EHMT2 gene in testicular support cells and then predicts the higher-order structures of sequences with and without AS. Two types of lentiviral vectors for overexpression were subsequently constructed for the EHMT2 gene, one with AS and one without, to infec...
Liu J, Yang Y, Wen L, Wen M, Zeng Y, Ren W, Yao X.The Kazakh horse is an outstanding dual-purpose dairy and meat breed in China, characterized by early maturity, tolerance to coarse feed, and strong stress resistance. Previous studies have examined gene expression patterns in the testicular tissues of Kazakh horses at different age stages, but the molecular mechanisms regulating testicular sexual maturation remain unclear. To address this gap, this study conducted HE staining and in-depth transcriptome sequencing analysis of Kazakh horse testicular tissue before and after sexual maturity. HE staining showed that the G3 group had well-formed s...
de Castro Sasahara TH, Gomes SP, Abdala FCM, Schimming BC, Miglino MA.Sexual differentiation in the equine fetus involves coordinated morphogenetic processes that shape both the gonads and the genital ducts. Although the formation of testes and ovaries has been relatively well documented, the temporal dynamics and morphometric patterns of the mesonephric (Wolffian) and paramesonephric (Müllerian) ducts remain insufficiently characterized. This study aimed to detail the timeline of gonadal and ductal differentiation in male and female equine fetuses during the critical developmental window between 60 and 80 days of gestation. Gross anatomical evaluation, histo...
Sancler-Silva YFR, Papa FO, Esteller-Vico A, Silva-Junior E, Oliveira TES, El-Sheikh Ali H, Boakari YL, Freitas MSE, Ball BA.This study evaluated the effects of oral pentoxifylline on testicular biometry, histology, and gene expression in stallions subjected to scrotal heat stress. Fourteen stallions were divided into three groups: Control (CRL, n = 4), Testicular Degeneration (DEG, n = 5), and Testicular Degeneration Treated with Pentoxifylline (DEG + PTX, n = 5). Testicular degeneration was induced by scrotal insulation, twice daily, over two consecutive days (D-1 and D0). Starting the next day (D1), oral pentoxifylline (17 mg/kg) was administered every 12 h for 30 days. Testicular biometry was measured ...
Maria Feitosa Ribeiro L, Bersot Gomes JV, Hernando Ortiz Vega W, da Silva Alves A, Netto Machado M, Junio Wutke L, Raquel Quirino C....Stallion breeding is mostly based on desirable phenotypic traits, with little consideration for semen quality. Objective: To identify relationships among semen parameters in stallions using a non-invasive, integrative approach across summer and winter seasons. Methods: Twenty-four stallions were evaluated, in which semen collections, testicular thermography, and Doppler velocimetry of the testicular artery by Doppler ultrasonography were performed, in addition to the measurement of physiological, environmental, and heat stress parameters, both in winter (coat weather) and summer (T-shirt weath...
Freitas Silva D, Passagli Barbosa D, de Paula Rodrigues J, Robaina Sancler-Silva YF, Saules Ignácio F, Lucena Fredou M, Segabinazzi L, Monteiro GA.Doppler ultrasonography is a valuable tool for monitoring testicular hemodynamics, offering improved diagnostic insight and supporting treatment monitoring. However, its use in equine andrology remains limited due to a scarcity of published data and reference values. Therefore, this study aimed to characterize the testicular arterial blood flow patterns in clinically normal stallions and stallions with 180° spermatic cord torsion. Spectral Doppler ultrasonography was performed on both testes of 48 Mangalarga Marchador stallions. Thirty stallions with normal testes were divided into three age ...
Fain H, Hendrickson DA, Buesing MT, Griffenhagen G.Cryptorchidism is a common congenital disorder in male horses characterized by the failure of one or both testes to descend into the scrotum. This developmental anomaly has important clinical, surgical, and economic implications, particularly in breeding animals. This retrospective study investigates the prevalence and laterality of cryptorchidism in a large equine population presented to two veterinary referral hospitals-Colorado State University Veterinary Teaching Hospital (CSU VTH, 1984-2014) and Oakridge Equine Hospital (OEH, 2008-2023). Medical records were reviewed to identify affected ...
Hegger A, Köhne M, Gerhauser I, Görgens A.A 19-year-old Oldenburg stallion was presented multiple times over the course of several months with recurrent colic signs. At each examination, an enlargement of the scrotum was noted, which could not be further specified by palpation and ultrasonographic examination. The increase in circumference was noted both on palpation and on inspection and the size remained unchanged throughout. No special findings were noted during the general examination and the special examination of the colic patient. A few months after the first onset of symptoms, a chicken egg-sized mass was palpated on the right...
Shakeel M, Yoon M.Brain-derived neurotrophic factor (BDNF) and its receptor neurotrophic tyrosine receptor kinase-2 (NTRK2) have known important roles in the central nervous system for neurite growth, survival, and differentiation. Nevertheless, the significance of BDNF in spermatogenesis remains unclear in stallions. Therefore, the present study was designed 1) to investigate the expression of BDNF and its receptor NTRK2 and 2) the seasonal variation in the expression patterns of BDNF and NTRK2 in stallions' testes. We used testes from eight postpubertal Thoroughbred stallions collected after a field castratio...
