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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.
Sperm morphology in stallions: ultrastructure as a functional and diagnostic tool. Conventional light microscopic evaluation of a seminal ejaculate does not fully avail potential indicators of functional impairment in spermatozoal organelles. The technique of critical quantitative evaluation of morphologic features of individual structural components of spermatozoa at a light microscopic level in conjunction with critical qualitative evaluation of spermatozoal organelles at an ultrastructural level, as described in this article, is a valuable clinical tool. Compared with a battery of sperm function assays used in human andrology clinics, this relatively less expensive and si...
Advanced methods for handling and preparation of stallion semen. Clinical reproduction in the horse more closely parallels human clinical reproduction than in other domestic farm animals. Horse breeders rarely include fertility as a selection criterion when making mating decisions; in most breeds, there is no licensing or approval of stallions. This has led to a significant number of stallions in the breeding pool that possess desirable performance traits but are subfertile for a variety of reasons, some of them genetically transmitted between generations. Therefore, semen characteristics can vary greatly among stallions within the breeding population. A ch...
Advanced insemination techniques in mares. Advanced artificial insemination techniques, such as deep uterine,hysteroscopic, oviductal, and intrafollicular insemination, are described in the context of the different types of spermatozoa that are now available for insemination, including fresh, chilled, frozen,sex-sorted, and epididymal spermatozoa. The implementation of these new technologies answers and poses questions about the interactions of sperm and oocytes in vivo.
Laparoscopic cryptorchidectomy and ovariectomy in horses. Laparoscopic surgery has become commonplace in the field of equine urogenital surgery. As with most surgical procedures, the limiting factors in developing new surgical techniques are limited to the patient size and demeanor, the skills of the surgeon, and the available equipment. Some of the greatest benefits of laparoscopic surgery in the horse include better visualization of the important structures; tension-free amputation of the testes or ovaries,which generally leads to less postoperative pain; and the ability to evaluate the transected stump carefully to make sure there is no hemorrhage...
Viability and acrosome staining of stallion spermatozoa by Chicago sky blue and Giemsa. A simple trypan blue-neutral red-Giemsa staining procedure for simultaneous evaluation of acrosome, sperm head, and tail membrane integrity and morphology has been used to evaluate equine spermatozoa. Some special characteristics and problems have arisen in evaluating stallion semen. One problem was the differentiation of intact vs. damaged sperm tails primarily in frozen and thawed samples. After freezing and thawing, a high percentage of spermatozoa with an unstained head and stained tail were observed. These cells are considered immotile. Therefore, unambiguous differentiation of intact vs....
Collection and freezing of epididymal stallion sperm. The ability to harvest and preserve epididymal sperm from a stallion after simple elective castration, a catastrophic injury, or severe acute illness and subsequent death has been realized, allowing for the preservation of genetics that would have been lost otherwise.Currently, the care taken to collect the testes and epididymides properly, coupled with proper packaging and shipping, could make the greatest contribution to salvaging viable sperm. As advances in assisted reproductive techniques continue, more offspring may be obtained from stored epididymal sperm from valuable stallions.
Prevalence of mycoplasmas in the semen and vaginal swabs of Danish stallions and mares. The reproduction rate of horses is one of the lowest within domestic livestock despite advances the veterinary medicine. Infertility in horses may be due mainly to the lack of suitable selection criteria in the breeding of horses. However, acquired infertility due to genital, bacterial infections may occur. Mycoplasmas have been implicated in genital disorders and infertility of many species including humans and horses. However, their role as commensals or pathogens of the genital tract of horses is still not determined. Bacteriological examinations made on the fossa glandis, urethra, penis an...
Effects of mating on plasma concentrations of testosterone, cortisol, oestrone sulphate and 15-ketodihydro-PGF2alpha in stallions. Very little information is available regarding the physiological mechanisms involved in the normal sexual activity in the stallion and, in particular, the endocrine control of reproduction is still not clearly understood. This experiment was designed to determine the short-term effect of sexual stimulation on plasma concentrations of testosterone, cortisol, oestrone sulphate and 15-ketodihydro-PGF(2alpha) in stallions. Semen samples were collected from 10 lighthorse stallions of proven fertility using a Missouri model artificial vagina. At the same time, blood samples were collected from the j...
Anti-oxidative status and semen quality during cooled storage in stallions. Activity of the anti-oxidative enzymes glutathione peroxidase (GSH-Px), superoxide dismutase (SOD) and catalase (CAT), content of thiobarbituric acid reactive substances (TBARS) and SH-groups were determined in native stallion semen (n = 8 stallions). Semen was then diluted in Kenney extender, EquiPro((R)) extender either with or without addition of N-acetyl cysteine or phosphate-buffered saline (PBS) and stored for 72 h at 5 degrees C. Correlations between initial activity of enzymes and development of semen motility and membrane integrity were calculated. Activities of GSH-Px, SOD and CAT im...
Effect of seminal plasma fractions on stallion sperm survival after cooled storage. This study aimed to evaluate stallion sperm survival after 24 h of cooled storage in the presence of seminal plasma (SP) derived from the sperm-rich fractions (SRF) or sperm-poor fractions(SPF) of the ejaculate, without SP, or in the presence of SP from other stallions. Ejaculates were collected from four stallions using an automated phantom, which separated the semen into five cups. Centrifuged and washed spermatozoa from cup 2 (SRF) were mixed with skim milk extender to a concentration of 100 x 10(6) sperm/ml and then 1:1 (v/v) with SP from the stallion's own or another stallions' second (SP...
Post-testicular changes in the density and distribution of intramembrane particles of stallion sperm surface domains. Freeze-fracture replicas of stallion spermatozoa, collected from the proximal caput, corpus and cauda epididymides regions, were analyzed by electron microscopy to explore the distribution and density of intramembrane particles (IMP). Conspicuous differences in density and arrangement of the IMP were observed in the different topographical domains of mature and immature spermatozoa. A reduction of IMP, especially remarkable in the post-acrosomal domain, was observed in mature epididymal spermatozoa when compared with samples collected from ductuli efferentes. Some structural species-specific d...
Effects of flunixin meglumine on selected clinicopathologic variables, and serum testosterone concentration in stallions after endotoxin administration. Four clinically normal stallions were infused intravenously with endotoxin (LPS) from Escherichia coli 055:B5 at a dose of 0.3 microg/kg b.w. and four stallions were treated with flunixin meglumine (FM) as a single intravenous injection at a dose of 1.1 mg/kg b.w., 5 min after the infusion of LPS. In response to endotoxin infusion, stallions' reaction was fever (increased rectal and scrotal skin temperature), increased heart rate (HR) and leucopenia. Administration of endotoxin also influenced the level of testosterone (decrease at 3-24 h and increase at 48-72 h after LPS administration) in th...
Fertility of frozen-thawed stallion semen cannot be predicted by the currently used laboratory methods. The aim of the project was to use current simple and practical laboratory tests and compare results with the foaling rates of mares inseminated with commercially produced frozen semen. In Exp. 1, semen was tested from 27 and in Exp. 2 from 23 stallions; 19 stallions participated in both experiments. The mean number of mares per stallion in both experiments was 37 (min. 7, max. 121). Sperm morphology was assessed and bacterial culture performed once per stallion. In Exp. 1, progressive motility after 0, 1, 2, 3, and 4 h of incubation using light microscopy, motility characteristics measured wit...
Reproductive tract infections in horses. Diagnosis, treatment, and, ultimately, prevention of reproductive disease are vital components of equine veterinary medicine. A thorough understanding of anatomy and physiology is necessary to reconcile the pathologic findings of disease. Only then can a rational treatment plan be formulated. Many recent advances in knowledge about the reproductive system of multiple species have application to the mare and stallion.
Effect of exercise and suspensory on scrotal surface temperature in the stallion. In this study, the effect of exercise (treadmill, riding) on scrotal surface temperature (SST) in the stallion with and without suspensory was evaluated. Experiments were carried out between September and November 2004 using 12 Franches-Montagnes stallions from the National Stud in Avenches (Switzerland). Each stallion performed a standardized incremental treadmill and a ridden test with and without suspensory. The intensity of exercise was monitored by heart rate and blood lactate concentration. For SST measurements, special thermistors were developed and affixed to the most ventral part of t...
Developments in European horse breeding and consequences for veterinarians in equine reproduction. The liberalization of European animal breeding legislation and an increasing diversity of equestrian sports have led to a constant rise in the number of horse breeds and breed registries. In addition to the trend towards more and smaller breed registries, there is another trend towards an international expansion of the bigger established sport horse breeds. Regional breeds, at least in smaller countries, may no longer be able to run an independent breeding programme. The typical horse breeder, in the future, will be a female and qualified in equestrian sports. Artificial insemination (AI) main...
Disease transmission in horses. Bacterial, viral and protozoal infections may cause severe reproductive losses. The present paper reviews the risk factors, clinical signs and preventive measures for the most important venereal or potential sexually transmitted diseases in horses. The stallion and use of semen for artificial insemination represent major risk factors for the transmission of bacterial contaminants of the penis, including Streptococcus equi subspecies zooepidemicus, Pseudomonas aeruginosa and Klebsiella pneumoniae, known to cause endometritis and infertility in the mare. The role of the stallion in disease trans...
Clinical, cytogenetic and hormonal findings in a stallion with hypospadias–a case report. This case report describes a three-year-old Friesian stallion with hypospadias. Physical examination revealed a ventrocaudal deviation of the shaft of the penis and an incomplete glans penis. The urethral opening was 4 cm in length, slit-like and had a mucous membrane covering. A short fold ran from the ventral aspect of the anus and ended with a non-pigmented hairless area of skin. A human choriongonadotropin (hCG)-stimulation test resulted in an increase in the plasma levels of estrogen sulfate and testosterone, indistinguishable from that of a normal stallion. The karyogram had a normal num...
Detection of an epidermoid cyst in the foot of a horse by use of magnetic resonance imaging. CASE DESCRIPTION-A 4-year-old Quarter Horse stallion was evaluated because of a 10-month history of moderate (grade 3/5) left forelimb lameness (detectable during trotting over a smooth, hard surface). CLINICAL FINDINGS-No abnormalities were detected in either forelimb via palpation or application of hoof testers; however, lameness was eliminated after administration of a palmar digital nerve block in the left forelimb. Whereas radiography and ultrasonography did not identify any left forelimb foot abnormalities, magnetic resonance (MR) imaging revealed a circumscribed soft tissue mass in the ...
Influence of immunization against GnRH on reproductive cyclicity and estrous behavior in the mare. The aim of this study was to evaluate the effect of active immunization against GnRH on ovarian activity, plasma progesterone and estradiol concentrations and on estrous behavior in adult mares. Eighteen cyclic mares were randomly divided into a treatment and control group. Nine mares were immunized twice with 2 mL (400 microg GnRH-protein conjugate) of a GnRH-vaccine (Improvac, CSL Limited, Australia) administered intramuscularly, 4 weeks apart. Control mares received the same amount of saline solution. Ovaries and uterus of all mares were examined weekly by ultrasonography from 3 weeks befor...
Insemination doses: how low can we go? This manuscript presents a brief historical review of investigations related to equine artificial insemination. The origin of recommended insemination doses for use fresh, cooled and frozen semen will be reviewed. Over 30 years ago, an insemination dose of 500 x 10(6) progressively motile sperm (PMS) was recommended to maximize pregnancy rates when mares were bred with fresh semen under less than ideal conditions. Since that time, 500 x 10(6) progressively motile sperm has been almost universally accepted as a standard insemination dose, regardless of a stallion's fertility or the refinements ...
Comparison of three containers used for the transport of cooled stallion semen. Three containers commonly used to transport cooled equine semen (Equitainer, ExpectaFoal and a Swedish-designed semen-transport container, previously called the Salsbro Box and now called Equine Express) were compared, using four ejaculates from each of three stallions. Each ejaculate was diluted to a spermatozoal concentration of 25 x 10(6)/ml with a nonfat dry milk-glucose extender containing amikacin sulfate (1 mg/ml) and potassium penicillin G (1000 units/ml). Extended semen was divided into three 40-ml aliquots for placement in each of the three semen-transport containers. The extended se...
Equine frozen semen: freezability and fertility field results. The freezability of stallion semen defined as the number of selected ejaculates/total number of ejaculates frozen from 161 different stallions was analyzed. Of the stallions, 19, 30, 27 and 24% had a freezability of 0%, 0 to 33%, 33 to 66%, over 66%, respectively In 85 different stallions, the correlation of freezability between first and second year was 0.60 (P < 0.001). The relationship between fertility with fresh and frozen semen and freezability was analyzed in 40 stallions whose freezability and fertility information was recorded during 5 years. There was a strong relationship between fe...
Factors affecting spermatogenesis in the stallion. Spermatogenesis is a process of division and differentiation by which spermatozoa are produced in seminiferous tubules. Seminiferous tubules are composed of somatic cells (myoid cells and Sertoli cells) and germ cells (spermatogonia, spermatocytes, and spermatids). Activities of these three germ cells divide spermatogenesis into spermatocytogenesis, meiosis, and spermiogenesis, respectively. Spermatocytogenesis involves mitotic cell division to increase the yield of spermatogenesis and to produce stem cells and primary spermatocytes. Meiosis involves duplication and exchange of genetic materia...
New staining methods for sperm evaluation estimated by microscopy and flow cytometry. New staining methods and automated instruments are now available to evaluate the sperm cell in vitro. Individual compartments of the sperm cell, such as the nucleus and the plasma and acrosomal membranes, may be investigated, as well as the cell function as shown by mitochondria activity and capacitation. Various probes are used and they can be analyzed by direct light or fluorescent microscopy or by flow cytometry. The automated instruments allow objective and accurate analysis and quantification as well as the ability to evaluate large population of cells in a shorter time, thus providing ac...
Determination of acrosin amidase activity in equine spermatozoa. Acrosin amidase activity of spermatozoa has been been associated with in vitro fertilization success in humans and has been proposed as an additional method for assessing sperm function in vitro. In this study, acrosin amidase activity was determined in equine spermatozoa by the hydrolysis of an arginine amide substrate. This assay includes a detergent to release acrosomal enzymes into a medium of basic pH to activate proacrosin to acrosin, which subsequently hydrolyses N-alpha-benzoyl-DL-arginine para-nitroanilide-HCl (BAPNA) to a chromogenic product. Spermatozoa (n = 3 ejaculates from each o...
Cholesterol-to-phospholipid ratio in whole sperm and seminal plasma from fertile stallions and stallions with unexplained subfertility. Semen samples were collected from six fertile stallions and seven stallions with unexplained infertility. Percentages of motile sperm (77.5 +/- 11.3 versus 67.5 +/- 12.2, P = 0.2), and progressively motile sperm (70.8 +/- 13.6 versus 60.7 +/- 14.0, P = 0.2) were similar between fertile and subfertile stallions, respectively. Morphologic characteristics in ejaculates of control and affected stallions (% normal: 60.2 +/- 18.2 versus 52.9 +/- 11.3, P = 0.4; % abnormal heads 7.3 +/- 4.8 versus 12.1 +/- 5.0, P = 0.11; and % abnormal acrosomes 1.6 +/- 2.1 versus 3.0 +/- 3.4, P = 0.4) did not differ....
Social relationships in a herd of Sorraia horses Part I. Correlates of social dominance and contexts of aggression. Factors related to dominance rank and the functions of aggression were studied in a herd of Sorraia horses, Equus caballus, under extensive management. Subjects were 10 adult mares 5-18 years old and a stallion introduced into the group for breeding. Dominance relationships among mares were clear, irrespective of rank difference, and remained stable after introduction of the stallion. The dominance hierarchy was significantly linear and rank was positively correlated with age and total aggressiveness. Higher-ranking mares received lower frequency and intensity of agonistic interactions. Nevert...
