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Topic:Stallion
Stallions are adult male horses that have not been gelded and are often used for breeding purposes. They exhibit distinct behavioral and physiological characteristics compared to mares and geldings. Stallions are known for their strong musculature, prominent neck, and often more pronounced mane and tail. Their behavior can be more aggressive and territorial, especially during the breeding season, as they naturally compete for mating opportunities. This topic explores the anatomy, behavior, and management practices specific to stallions, as well as their role in equine reproduction. The page provides access to peer-reviewed research studies and scholarly articles that investigate various aspects of stallion health, fertility, and behavior, contributing to the understanding and management of these horses in equine science.
Questionnaire-Based Investigation into Stallion Management Practices in 28 Countries. Modern stud farm practices may limit stallion social contact, with potential welfare and safety implications. Objective: To describe housing, management and safety outcomes for stallions kept at horse breeding operations throughout the world and to assess regional differences. Methods: An online questionnaire was distributed via mailing lists and WhatsApp; 116 complete responses from breeding operations were collected and analysed. The focus was on management of the breeding facility, and stallion welfare indicated by management, handling and housing. Results: Respondents were from Europe (40....
Effects of the Freezing Diluent Tonicity and Prefreezing Cooling Rates on Post-Thaw Sperm Quality Markers in the Pure-Bred Arabian Stallion. Stallion semen cryopreservation remains limited by inconsistent post-thaw sperm quality and fertility. This study evaluated the effects of freezing extender effective tonicity and prefreezing cooling rate on post-thaw sperm characteristics in pure-bred Arabian stallions. In a two-phase design, ejaculates ( = 40) from 10 stallions were processed using extenders with different osmotic conditions (330, 390, and 450 mOsm/kg) and subjected to cooling durations of 45 min, 1.5 h, or 3 h. Sperm quality was assessed using CASA, functional assays, flow cytometry, transcriptomic analysis, and...
Extreme male reproductive skew limits effective population size in American Standardbred horses. Standardbred horses are widely used for harness racing in North America, Europe, Australia, and New Zealand. In the U.S., two gaits (Pacers and Trotters) are genetically differentiated at a level typical for different horse breeds. We used the complete pedigree for all registered American Standardbred foals born 1970-2014 (>200 K Trotters and > 500 K Pacers) to calculate annual and lifetime reproductive skew and its consequences for the effective number of breeders per year (Nb) and effective size per generation (Ne). With rare exceptions, females can only produce 0 or 1 foal per year, w...
The Effect of Different Extenders and Testicular Anaesthesia During Orchiectomy on Post-Thawed Spermatological Parameters of Stallion Epididymal Spermatozoa. Cryopreservation of epididymal stallion spermatozoa is a valuable tool for fertility preservation, particularly after orchiectomy. However, the potential interactions between local anaesthesia and extender composition on post-thaw spermatozoal quality remain poorly understood. This study investigated the effects of intratesticular lidocaine injection and the efficacy of various extender (egg yolk [EY] vs. lecithin [LC]) and cryoprotectant (glycerol [GLY] vs. dimethyl sulfoxide [DMSO]) combinations on stallion epididymal spermatological parameters. Using a paired factorial design, epididymal s...
Testicular Disorders in Equids: A Case Series. Equine testicular disorders represent a diverse group of conditions that impact the longevity of a stallion's breeding career. Stud farm veterinarians should be familiar with the variety of clinical presentations and diagnostic options for these conditions. This retrospective case series reports 57 cases of testicular abnormalities in stallions and donkeys presented to the clinic for further diagnostics and treatment. These disorders included neoplasia (three unilateral and one bilateral seminoma; two Sertoli cell tumors; two Leydig cell tumors; and one malignant mixed sex cord-stromal tumor),...
Body Condition, Metabolic Parameters and Semen Traits in Purebred Spanish Horses. The growing relevance of the Purebred Spanish horse has driven the extensive use of assisted reproductive technologies to preserve elite stallion genetics. Optimal reproductive performance is intrinsically linked to systemic health and high semen quality. This study aimed to evaluate the impact of body condition on the stallion's metabolic and endocrine profiles and their seminal parameters. Semen and blood samples were collected from 26 stallions (February-May in 2024-2025) whose body condition score (BCS) was assessed using the Henneke scale. They were classified into two groups, low BCS wit...
Combined effects of pre-freeze cholesterol-loaded cyclodextrin and post-thaw pentoxifylline on the functional longevity of cryopreserved stallion sperm. Cryopreservation causes structural and metabolic damage to stallion spermatozoa, impairing post-thaw functional competence. Objective: This study evaluated whether cholesterol-loaded cyclodextrin (CLC) supplementation before freezing, combined with pentoxifylline (PTX) after thawing, improves the functional quality, oxidative status, mitochondrial activity, and preliminary fertility outcomes of cryopreserved stallion semen. Methods: Semen from twelve stallions was assigned to four CLC concentrations (0, 1, 1.5, and 2 mg), frozen, thawed, and divided into subgroups with or without PTX supplemen...
The effect of fenugreek (Trigonella foenum-graecum) on stallion spermatozoa motility and vitality in vitro. This study evaluated the effects of Trigonella foenum-graecum L. (fenugreek) seed extract on stallion spermatozoa quality in vitro, focusing on motility, vitality, and functional competence. In vitro spermatozoa analyses showed that fenugreek seed extract did not demonstrate overt cytotoxicity under the tested conditions: S1 = 1562 µg/mL; S2 = 781 µg/mL; S3 = 390.5 µg/mL; S4 = 195.25 µg/mL; S5 = 97.62 µg/mL; S6 = 48.81 µg/mL; S7 = 24.40 µg/mL. Computer-assisted semen analysis (CASA) revealed a concentration- and time-dependent Treatment × Time interac...
Isolation of high-quality stallion spermatozoa: a comparison of methods and their effects on sperm quality and yield, DNA damage, and functional competence by ICSI. Intracytoplasmic sperm injection (ICSI) is the primary method for equine in vitro embryo production, yet outcomes may be influenced by sperm selection techniques. Objective: This study compared four isolation methods: EquiPure™, Vetmotl™, Felix™, and Samson™, to assess effects on sperm quality and embryo development. Methods: Semen was collected from four fertile stallions, processed and evaluated for sperm motility, viability, DNA integrity, and yield of high-quality cells relative to input. Isolated samples were compared to non-isolated (centrifuged) samples. Spermatozoa were used fo...
Behaviour and Movement Activity of Stallions and Geldings in Group Housing. There has been little research on the social behaviour of stallions and geldings kept together in group housing systems. The aim of this study was to investigate differences in behaviour and movement activity between stallions and geldings kept together in group housing. Behavioural observations and GPS measurements were conducted in Germany from July to September 2024 in four mixed groups of horses in Germany. The groups comprised 35 animals, 18 stallions and 17 geldings. The horses were observed for three consecutive days over eight hours per day. No injuries or stereotypic behaviours were o...
Factors Influencing Equine Embryo Outcomes in OPU‑ICSI Systems: Insights from a Large‑Scale Program in Brazil. Equine OPU‑ICSI supports commercial IVEP, yet substantial variability persists. We retrospectively analyzed a large dataset generated in Brazil spanning Quarter Horses, Warmbloods, and Mangalarga to evaluate whether predictors previously identified in the literature show comparable patterns under distinct ecological and breeding conditions. Overall oocyte and embryo outcomes were aligned with broadly reported trends from previous studies. Oocytes retrieved from estrous mares bearing a dominant follicle exhibited higher maturation and blastocyst rates. Stallion effects segregated into distinc...
Genetic Diversity in Domestic Horses: Temporal Patterns, the Influence of Assisted Reproductive Technologies, and Implications for the American Quarter Horse. Genetic diversity is the heritable variation within and among populations and is essential for the long-term health and selection potential of domestic horses. Previous studies show diversity across breeds is shaped by effective population size, founder events, artificial selection, and levels of inbreeding. While some closed-studbook breeds retain moderate genetic diversity, others have experienced rapid losses due to popular-sire effects and recent and extensive inbreeding. Even so, mare lines continue to help maintain genetic diversity within these populations. Assisted Reproductive Technol...
Untargeted Sweat Metabolomics and Targeted Plasma Amino Acid Profiling Reveal Dynamic Metabolic Remodeling During Conditioning in Yili Horses. Training induces sweat morphology changes in horses from muddy sweat (MS) to foamy sweat (FS) and clear sweat (CS), reflecting physiological adaptation. However, the metabolic mechanisms linking sweat phenotypes to systemic amino acid dynamics remain unclear. This study integrated sweat untargeted metabolomics and plasma amino acid targeted metabolomics to reveal coordinated metabolic remodeling. Six 2-year-old horse stallions underwent 10-week training. Plasma and sweat were sampled pre- and post-race at each stage. LC-MS/MS and UHPLC-MS/MS were used for sweat metabolome and plasma amino aci...
Advanced paternal age is associated with reduced reproductive success and offspring racing performance in Australian Thoroughbred racehorses. Reproductive ageing influences fertility and offspring fitness across mammals. In humans and model organisms, paternal age has been associated with changes in sperm quality and genomic integrity, including oxidative stress, DNA damage, and epigenetic alterations; however, these mechanisms have not been directly examined in large equine populations. Thoroughbred racehorses provide a system to investigate paternal age effects at scale using detailed breeding records. In this retrospective observational study, with data from 35 retired stallions and 33,546 progeny, we assessed associations betwee...
The progression values of heart rate and biochemical plasma parameters during training of 3-years old warmblood stallions for breeding licensing. Physiological adaptation to training in young sport horses remains incompletely characterized, particularly during standardized preparation for breeding licensing. Objective: The aim of this study was to evaluate cardiovascular and plasma biochemical responses to acute exercise and long-term training in three-year-old Czech Warmblood stallions during standardized free jumping exercise. Methods: Thirteen Czech Warmblood stallions were monitored over a 112-day training period. Heart rate parameters (minimum, maximum, and mean) were recorded during standardized free jumping tests. Plasma biochemi...
Achieving Success in Conventional Equine Embryo Transfer: A Practical Review. Equine embryo transfer is a well-established procedure in horse breeding programs and it's used to increase the number of offspring from valuable mares, obtain embryos from mares in competition and produce foals from mares unable to carry a pregnancy to term. The success of embryo recovery depends mainly on the day of flushing, management of insemination, and the fertility of donor mare and stallion. Other relevant factors include donor age and reproductive status, number of ovulations, operator experience, and flushing technique. Pregnancy rates after transfer are influenced by donor-recipien...
Sport predispositions in warmblood horses: insights from Grand Prix competitions. The aim of this study was to pilot the assessment of sport predispositions in warmblood horse breeds, both domestic and foreign, and to evaluate factors influencing their performance. Data from 293 horses (725 starts) competing in national Grand Prix events with obstacle heights of 140-145 cm were analysed using general mixed models. The origins of Polish Halfbred Horses were examined, and correlations between results in the Young Horse Championships and later Grand Prix performance were assessed. Results showed that performance is significantly influenced by genetic factors, such as breed and...
Effect of Spirulina platensis extract (C-phycocyanin) supplementation to the semen extender on kinematic and oxidative parameters of Marwari stallions during freezing. The current research aimed at examining the impact of different quantities of Spirulina platensis extract (C-phycocyanin) supplemented to the semen extender on the post-thaw quality of Marwari stallion spermatozoa. Semen samples were obtained via an artificial vagina from six fertile stallions and diluted with an extender containing Spirulina platensis extract (C-phycocyanin) at concentrations of 10, 20, and 50 µg/mL, or without Spirulina as a control. Aliquots of diluted semen were subjected to cooling (4 °C, 120 min) and then frozen (-196 °C, 1 day), after which the kinematic paramet...
Effect of Antioxidant Supplementation on Systemic Oxidative Status in Breeding Stallions During Intensive Semen Collection. Breeding stallions are subjected to increased metabolic and physiological demands during the reproductive season, which may lead to enhanced production of reactive oxygen species and disruption of redox balance. The present study evaluated the effects of dietary antioxidant supplementation on oxidative status, metabolic profile, and hindgut fermentation in stallions undergoing intensive semen collection activity. Ten adult breeding stallions were assigned either to a control group or to a treatment group receiving a commercial antioxidant supplement (Oxyliver) for 60 days, followed by a 60-day...
Prevalence, genomic diversity and emerging antimicrobial resistance of Taylorella asinigenitalis in Grand Noir du Berry breeding donkeys. Taylorella asinigenitalis is a fastidious Gram-negative bacterium of the equine genital tract, found more commonly in donkeys than horses. Although considered non-pathogenic, it is closely related to Taylorella equigenitalis, the agent of contagious equine metritis, and has been linked to experimental and natural cases of endometritis. The SAFRAN project (French acronym for "Sauvegarde de la fertilité de l'âne", meaning "Preservation of donkey fertility"), launched in 2024 by the French National Research Institute for Agriculture, Food and Environment (INRAE) with support from the Centre-Val...
Annual Variation in Stallion Testicular Measurements and Its Association With Hormonal Profiles and Semen Quality. In a stallion breeding-soundness examination, testicular volume may be estimated either from total scrotal width or by measuring the height, width and length of both testes. This study aimed to determine whether testicular morphometric parameters obtained by ultrasonography fluctuate throughout the year, and whether these variations affect semen quality and hormone production in stallions located at low latitudes in the Southern Hemisphere. Eight healthy light-breed stallions were evaluated every 15 days for 1 year, encompassing the breeding (October-April) and non-breeding(May-September) ...
The Role of Omega-3 Fatty Acids in Horses’ Nutrition-A Review. This narrative review presents examples of omega-3 fatty acids supplementation in horse nutrition. Fats are essential in equine nutrition, serving not only as an energy source but also as functional components influencing health. Among them, omega-3 polyunsaturated fatty acids (PUFAs), particularly EPA and DHA, play a key role in modulating inflammatory and metabolic processes. This review summarizes their effects on respiratory health, equine metabolic syndrome (EMS), musculoskeletal function, reproduction, and early development. Omega-3 supplementation has been shown to support airway inflam...
Conventional IVF in the horse past, present, and future: physiological and technical insights. For decades, conventional in vitro fertilization (IVF) in the horse was ineffective, leading to reliance on intracytoplasmic sperm injection (ICSI) for both research and clinical in vitro embryo production. However, the ability to achieve IVF is essential to the study of key reproductive processes, including sperm capacitation, fertilization, and early embryonic development. Recently we have established a repeatable and efficient IVF system for horses, using long-term (9-22 h) sperm pre-incubation. For clinical use, IVF has many features that may support higher embryo quality than does ICSI, a...
Factors influencing gestation length in Mares in the Tiaret region, Algeria. Gestation length is a key parameter in equine reproductive management, yet its variability remains poorly documented in Barb and Arabian mares under Algerian conditions. Objective: This study aims to determine gestation length in mares and to assess the influence of various factors, including breed, year of mating, mating month, mare age, parity, reproductive status, stallion and the foal's sex on gestation duration. Methods: A total of 133 mares from the National Stud Farm of Tiaret (Algeria) were monitored over the period 2021-2024. Results: The mean gestation length was 332.5 days (range: 3...
The Equine Reproductive Microbiota: Composition, Dynamics, Dysbiosis, and Implications for Fertility in Mares and Stallions. The equine reproductive microbiota has emerged as an important factor influencing reproductive health and fertility in both mares and stallions. Traditionally, the equine uterus was considered sterile, and microbial presence was interpreted primarily in the context of infection. However, sequencing-based studies have demonstrated that the reproductive tract, including the uterus and semen, contains detectable microbial communities or microbial DNA signatures, challenging this traditional paradigm. In mares, the vaginal microbiota is consistently dominated by , , , and , whereas the uterine env...
Nano-Encapsulated Vitamin E Enhances Cryo-Resistance of Stallion Spermatozoa: A Comprehensive Evaluation of Sperm Quality, Kinematic Parameters, Antioxidant Capacity, Microbiota and Ultrastructure. This experiment explores the comparative ability of vitamin E (VE) and its nano-emulsion (VEN) in enhancing cryo-resistance of stallion spermatozoa by examining semen quality, kinematic variables, acrosome integrity, apoptosis, antioxidant capacity, ultra-structural alterations and microbiota of cryopreserved stallion sperm. Semen from five stallions (8-10 years) was cryopreserved with 0.1 or 1 mM of VE or VEN; and a non-additive group served as the control. The VEN particles ranged in size from 72 to 172 nm, with a mean diameter of 287 nm. Supplementation with VE (1 mM) or VEN (0.1 ...
miRNA Sequencing and Differential Analysis of Testis in 1-Year-Old and 2-Year-Old Kazakh Horses. The represents a significant genetic resource within China's population, characterized by notable resilience and an ability to thrive on coarse forage. Nevertheless, a decline in its numbers has been observed recently, making the improvement of its reproductive performance crucial for the preservation of this breed and the advancement of the related industry. In this study, testicular tissues from 1-year-old (pre-pubertal) and 2-year-old (post-pubertal) were analyzed. miRNA sequencing was conducted on tissues from these age groups, followed by bioinformatics analyses to elucidate the functi...
Hyperactivation and Tyrosine Phosphorylation of Cryopreserved Stallion Spermatozoa in Relation to Conventional In Vitro Fertilization Blastocyst Production. Challenges in establishing clinical conventional in vitro fertilization (IVF) in horses include variation in sperm and oocyte quality, which can be affected by mare age. Extended preincubation of stallion spermatozoa has resulted in successful IVF. However, there is limited research on the impact of preincubation on sperm characteristics and IVF success. Objective: Responses of frozen-thawed stallion spermatozoa over time under IVF preincubation conditions were evaluated, and samples based on specific responses were tested for their ability to fertilize oocytes, including those from older mare...
Membrane and mitochondrial antioxidants improve post-thaw functional quality of stallion spermatozoa. Cryopreservation of stallion semen induces oxidative stress that compromises sperm motility, membrane integrity, and mitochondrial function. Given the high mitochondrial reliance of equine spermatozoa and their susceptibility to oxidative damage, compartment-specific antioxidant strategies may improve post-thaw functional resilience. This study evaluated the effects of astaxanthin, a membrane-active carotenoid, and MitoTEMPO, a mitochondria-targeted superoxide scavenger, on the functional and oxidative status of frozen-thawed stallion spermatozoa. Ejaculates from nine stallions were cryopreser...
ProAKAP4 as a predictor of semen freezability in Asturcon ponies. Cryopreservation is a valuable tool in equine reproduction, although its success remains highly variable among stallions. The proAKAP4 protein has been proposed as a molecular marker of sperm quality and cryotolerance. Objective: This study aimed to evaluate the relationship between proAKAP4 concentration and sperm cryotolerance in ejaculates from Asturcon ponies, and to assess whether proAKAP4 levels in fresh semen can predict post-thaw sperm quality parameters before and after cryopreservation. Methods: Twenty-four ejaculates from eight different stallions were used (three ejaculates per ani...
