Evaluation of equine semen frozen in extenders free of egg yolk using two different freezing curves

A chemically defined cryopreservation extender that maintains seminal parameters is relevant. Fifteen ejaculates from 5 stallions (n= 5; r=3) were diluted in 5 extenders: 1) EDTA-glucose based extender with egg-yolk and dimethylformamide (EY); 2) commercial equine extender (CE); 3) CE with dimethylformamide (CE-3); 4) bovine commercial extender with liposomes (OP); 5) bovine commercial extender with soybean lecithin (BIO), and frozen using a slow and a rapid temperature descent curve. Post-thaw evaluations were: sperm kinematic parameters, viability and acrosome status, membrane lipoperoxidation and DNA fragmentation. Sperm data were analysed using an ANOVA or Friedman test (results mean ± SD). Paired comparison between the two freezing curves was analysed using the Wilcoxon test. Total and progressive motility were significantly higher (P<0.05) in the EY and CE-3 samples using the slow curve, whereas for the fast curve, total and progressive motility were significantly higher (P<0.05) in the EY samples compared to all the extenders and the samples frozen in CE-3 were significantly higher than the remaining extenders (P<0.05). The percentages of live acrosome intact sperm and of live non-peroxidized sperm were significantly higher (P<0.05) in the EY extender when using either of the freezing curves and in turn, were significantly higher (P<0.05) in samples frozen in CE-3 compared to the remaining extenders. Intact DNA was significantly lower (P<0.05) in the BIO extender, using the rapid curve. To conclude, the commercial equine extender with 3% dimethylformamide, without egg-yolk, could be a suitable alternative for extenders with animal proteins.

Vibration emissions affect the quality of liquid-preserved AI doses in stallions

Artificial insemination (AI) with liquid-preserved stallion semen is a widely used reproductive technology. As the demand for AI doses of high-class stallions is transnational, they are frequently exposed to long-distance transport. Since recent studies in boars indicated that vibration emissions caused by transport negatively affected sperm quality in vitro, this study questioned whether sperm quality in stallions is similarly impaired. Furthermore, we investigated stallion and extender-related differences in the spermatozoa's resistance to transport-related quality loss. Stallion ejaculates (n = 30) were collected at a German AI center, split in half, and subsequently diluted to a final sperm concentration of 50 × 106 sperm/mL using the semen extenders EquiPlus or Gent (both Minitüb GmbH, Germany). Four 12 mL aliquots of each sample were filled in plastic syringes according to a split-sample design and exposed to vibration (Displacement index Di = 3.0 ± 0.1) at 5 °C for 0 h (control), 3 h, 6 h or 9 h. All samples were stored for four days at 5 °C after transport simulation and analyzed for total sperm motility, thermo-resistance, membrane integrity, and mitochondrial activity determined by flow cytometry as well as the pH. After calculating generalized linear mixed models for each sperm quality trait, a negative impact of the duration of transport simulation could be shown on total sperm motility (P = 0.001), thermo-resistance (P = 0.030), and the pH (P = 0.001). Simulated transport for 6 h and 9 h diminished sperm quality (P ≤ 0.01), with 9 h reducing thermo-resistance by 5 ± 2.2% points (PP) for EquiPlus and sperm motility by 2.2 ± 1.7 PP for Gent compared to the control group. In contrast, samples exposed to vibration for 3 h showed no decline in sperm quality (P > 0.05). The individual stallion influenced every semen trait (P < 0.05) and transport-related losses in sperm thermo-resistance of up to 15.9 PP were demonstrated. Furthermore, EquiPlus was superior to Gent in all semen assessments (P < 0.001). We conclude that in vitro sperm quality is impaired by vibration. As the quality loss depends on the transport time, we recommend keeping shipping time as short as possible especially for spermatozoa of stallions that are susceptible to vibration-induced sperm quality loss.

Effect of probiotics and prebiotics on the composition of the equine fecal and seminal microbiomes and sperm quality: A pilot study

Probiotic and prebiotic effects on equine semen and gastrointestinal microbiome composition and sperm quality are unknown. This study aimed to evaluate the effects of pre-, pro- or synbiotic supplementation on fecal and semen microbiome composition and sperm quality parameters of stallions. This Latin square crossover trial involved four miniature pony stallions receiving control diet only, or addition of a pro-, pre- or synbiotic formulation. Full-length 16S rRNA gene amplicon sequencing was used to measure diversity of semen and fecal microbiomes. Total sperm count, total motility, progressive motility, DNA integrity, lipid peroxidation and mitochondrial oxidative stress, biomarkers of sperm quality, were measured after each intervention. A general linear model was employed to analyse and compare microbiome diversity measures and sperm quality data across four time points. Shannon's diversity index (alpha-diversity), and evenness of semen and gastrointestinal microbiomes were significantly different (p<0.001). A trend was observed for prebiotic effects on the diversity indices of the GI microbiome (p= 0.07). No effects of treatments were observed on either semen microbiome or sperm quality. Pre-, pro- and synbiotic supplements showed no negative effect on sperm quality parameters observed. This proof of concept provides preliminary data to inform future studies exploring the relationship between microbiomes and fertility.

Comparison of two processing techniques on the sperm quality of semen contaminated with urine

Urospermia in stallions can occur intermittently, consistently, or as an isolated event, and may result in reduced sperm quality which is often assumed to reduce fertility. Although sperm quality declines in urospermic ejaculates, fertility has not been assessed in mares bred with urine contaminated semen. The aims of this study were to compare sperm quality after simple dilution (SD), cushioned centrifugation (CC) alone, or cushioned centrifugation combined with a 40 % silane-coated silica solution (SC) in semen contaminated with 0, 20, or 40 % (v/v) urine. Sperm quality values tended to decrease as the percent urine increased within all treatments (SD, CC, SC) after 24 h of cooled storage. However, SC treated groups had higher sperm quality compared to SD and CC when exposed to 20 or 40 % (v/v) urine. Differences in pregnancy rates among treatment groups (SD with 0 or 40 % (v/v) urine, or 40 % (v/v) urine followed by SC) were unable to be detected.

Protamine 2 and phospholipase C zeta 1 are possible biomarkers for the diagnosis of male subfertility in frozen-thawed stallion semen

Subfertility is one of the main issues in horse breeding and the study of mRNAs in sperm might help in elucidating the reasons that lead to this diagnosis. The present study aims at assessing the differences in the expression of 10 potential candidate genes in stallions of different fertility. Frozen-thawed semen of 29 stallions was included. Each sample was classified into two groups according to pregnancy rates (PR) achieved with this semen: "good fertility" (GF; n = 17; PR ≥ 30 %) or "poor fertility" (PF; n = 12; PR <20 %). All stallions underwent a breeding soundness examination (BSE) before semen production and were only included into the semen cryopreservation program when raw semen characteristics at BSE met minimal requirements. Semen was cryopreserved following European Union regulations and all stallions met the respective health requirements. Each sample was assessed for concentration (NucleoCounter SP-100), motility (CASA), membrane functionality (SYBR-14/PI), mitochondrial membrane potential (JC-1), morphology (SpermacStain), acrosome integrity (SpermacStain), membrane integrity (HOS test) and chromatin integrity (Aniline blue). Sperm RNAs were extracted using the Direct-zol RNA Miniprep Kit (Zymo Research) and RT-qPCR was performed for each target gene. ACTB and RPL32 were included as reference genes (RGs) for normalization. For each variable of each group, mean, standard deviation and SEM were calculated. The difference in gene expression levels between the GF and PF group were analyzed using the Mann-Whitney U test and Spearman's rank correlation. Significant results were considered with p < 0.05. Sperm quality parameters did not differ significantly between the two groups except for concentration, that was significantly higher in GF (p = 0.043). In GF a positive correlation was identified for PRM1/PRM2 with r = +0.6, while PRM1/ACR (r = -0.495), PRM2/ZPBP (r = -0.645) and CRISP3/ACR (r = -0.551) were inversely correlated. In PF direct correlations were registered for PRM1/PRM2 (r = +0.629), PRM1/PRM3 (r = +0.657), PRM2/SPA17 (r = +0.685), SPA17/PLCZ1 (r = +0.786) and PRM3/ACR (r = +0.627). In the total sample (GF + PF), positive correlations were detected for PRM1/PRM2 (r = +0.625), PRM1/PRM3 (r = +0.368); PRM2/SPA17 (r = +0.465), SPA17/PLCZ1 (r = +0.637) and PLCZ1/ZAN (r = +0.587). Only two of the genes considered were differentially expressed in the 2 groups: PRM2 and PLCZ1, that were significantly (p < 0.05) overexpressed in the GF group. Stallions frozen-thawed semen with higher expression levels of PRM2 and PLCZ1 are more likely to belong to animals with a good pregnancy rate. Further studies are needed to investigate the role of sperm transcripts in male subfertility in stallions.

Pyruvate enhances stallion sperm function in high glucose media improving overall metabolic efficiency

If a mechanism of more efficient glycolysis depending on pyruvate is present in stallion spermatozoa, detrimental effects of higher glucose concentrations that are common in current commercial extenders could be counteracted. To test this hypothesis, spermatozoa were incubated in a 67 mM Glucose modified Tyrode's media in the presence of 1- or 10-mM pyruvate and in the Tyrode's basal media which contains 5 mM glucose. Spermatozoa incubated for 3 h at 37 °C in 67 mM Tyrode's media with 10 mM pyruvate showed increased motility in comparison with aliquots incubated in Tyrode's 5 mM glucose and Tyrode's 67 mM glucose (57.1 ± 3.5 and 58.1 ± 1.9 to 73.0 ± 1.1 %; P < 0.01). Spermatozoa incubated in Tyrode's with 67 mM glucose 10 mM pyruvate maintained the viability along the incubation (64.03 ± 15.4 vs 61.3 ± 10.2), while spermatozoa incubated in 67 mM Glucose-Tyrode's showed a decrease in viability (38.01 ± 11.2, P < 0.01). 40 mM oxamate, an inhibitor of the lactate dehydrogenase LDH, reduced sperm viability (P < 0.05, from 76 ± 5 in 67 mM Glucose/10 mM pyruvate to 68.0 ± 4.3 %, P < 0.05). Apoptotic markers increased in the presence of oxamate. (P < 0.01). UHPLC/MS/MS showed that 10 mM pyruvate increased pyruvate, lactate, ATP and NAD+ while phosphoenolpyruvate decreased. The mechanisms that explain the improvement of in presence of 10 mM pyruvate involve the conversion of lactate to pyruvate and increased NAD+ enhancing the efficiency of the glycolysis.

Effect of quercetin, L-ergothioneine and H89 on sperm motility and kinematic pattern, plasma membrane functionality and in vitro heterologous fertilizing capacity of cryopreserved equine semen

Semen cryopreservation causes extensive chemical and physical damage to sperm structure, which generates premature aging and reduces viability and fertility of spermatozoa. The addition of antioxidants to freezing extenders can reduce the oxidative damage caused by excessive generation of reactive oxygen species (ROS), and the premature aging could be reduced by adding an enzyme inhibitor that prevents an anticipated capacitation. The aim of this study was to evaluate the in vitro effect of quercetin (Q), L-ergothioneine (E) and H89 addition to cryopreserved equine spermatozoa. Six experimental groups were stablished: control, Q, E, H89, H89Q and H89E. The analyzed parameters were sperm motility and kinematic using computer assisted sperm analysis (CASA), plasma membrane functionality with the hypoosmotic swelling test (HOST) and fertilizing capability with in vitro heterologous fertilization. Quercetin reduced curvilinear velocity (VCL) and increased beat-cross frequency (BCF), while its combination with H89 (H89Q) reduced total motility, progressive motility, VCL and hyperactive sperm (HA). Likewise, H89 and its combination with E (H89E) decreased VCL and amplitude of lateral head displacement (ALH). No significant differences were observed among treatments for membrane functionality and fertilizing capacity of sperm. In conclusion H89 in combination with Q and E reduced sperm motility or some kinematic parameters. However, they did not influence plasma membrane functionality and in vitro fertilizing capacity of frozen-thawed equine semen.

Short communication: Retrospective analysis of obligatory testing results for Equine virus arteritis reveals a decrease of its seroprevalence in stallions used for artificial insemination

Equine viral arteritis (EVA) can induce a persistent carrier state in stallions which then shed the virus via semen. About 30 years ago, obligatory EVA testing of stallions used for artificial insemination (AI) was implemented in the European Union. Information on the efficacy of these regulations on the prevalence of EVA in stallions are not yet available. Therefore, we retrospectively analyzed results of serological and virus antigen testing for EVA in sires of different age and breed referred to Vetmeduni Vienna for semen preservation or veterinary diagnostic procedures between 2001 and 2021. For analysis, stallions were grouped by age (1-5, 6-8, 9-12, >12 years) and breed. The EVA antibody titer was determined by serum neutralization test and semen was analyzed for EVA virus by PCR and/or virus isolation test. Of 308 stallions tested, 14.9% (n = 46) were EVA seropositive and in 12 stallions EVA virus was detected in semen (26% of seropositive stallions). The incidence of seropositive stallions decreased over time (P < 0.05, χ2 test). Differences in the seroprevalence of EVA antibodies existed among stallion age groups (P < 0.01, Fisher's test) with the highest percentage of seropositive stallions being > 12 years old (43.5%). The EVA antibody titer increased with age (P < 0.01, Kruskal-Wallis test), potentially reflecting repeated virus challenge. In conclusion, analysis of monitoring results revealed a decrease of EVA seroprevalence and virus shedding in a European sire population. As monitoring for EVA was the only measure implemented Europe-wide, testing might be a major contributor to this development.

Cellular and Molecular Consequences of Stallion Sperm Cryopreservation: Recent Approaches to Improve Sperm Survival

Cryopreservation of stallion semen does not achieve the post-thaw quality or fertility results observed in other species like cattle. There are many reasons for this, but the membrane composition and intracellular changes in stallion sperm predispose them to low resistance to the cooling, freezing, and subsequent thawing process. Damage to the sperm results from different processes activated during cryopreservation, including oxidative stress, apoptosis, and structural modifications in the sperm membrane that increase the deleterious effect on sperm. In addition, significant individual variability is observed among stallions in the ability of sperm to survive the freeze-thaw process. Recent advances in genomics, transcriptomics, proteomics, metabolomics, and epigenetics are making it possible to advance our understanding of the cellular and molecular processes involved in the cryopreservation process, opening new possibilities for improvement. This review addresses the ongoing research on stallion semen cryopreservation, focusing on the cellular and molecular consequences of this procedure in stallions and discusses the new tools currently available to increase the tolerance of equine spermatozoa to freeze-thaw.

Effects of therapeutic ultrasound and moderate heat on stallion testes

Transplantation of stem cells into dysfunctional testes is currently being investigated as a therapeutic option for men and stallions with advanced testicular degeneration. This series of "proof of concept" studies aimed to identify a safe and efficient method of inducing severe testicular degeneration to create an optimal equine recipient model for intratesticular stem cell transplantation (SCT). Two ex vivo and two in vivo experiments were conducted. At first, forty testes obtained from castrations were used to identify an effective therapeutic ultrasound (TUS) device and the protocol for increasing intratesticular temperature in stallions. Six min of treatment using the Vetrison Clinic Portable TUS machine raised the intratesticular temperature by 8°C-12.5 °C. This protocol was applied to treat three scrotal testes in three Miniature horse stallions, three times, every other day. Contralateral testes served as controls. There were signs of slight tubular degeneration in treated testes two and three weeks after TUS treatment. The number of seminiferous tubules (STs) with exfoliated germ cells (GCs) was increased in one testis only, three weeks after treatment. The degree of apoptosis of GCs was higher in each treated testis in comparison to the contralateral control testis. Next, the ability of various heating devices to increase intratesticular temperatures to at least 43 °C in stallion testes was tested, using twenty testes obtained from castrations. ThermaCare® Lower Back & Hip Pain Therapy Heatwrap (TC heat wrap) reliably increased intratesticular temperatures and kept them continuously between 43 °C and 48 °C for seven to 8 h. In the follow-up in vivo study, the left testes of three Miniature horse stallions were treated with TUS, after which both testes of each stallion were treated with moderate heat provided by the TC heat wrap (three times, every other day, for 5 h each time). There were signs of moderate tubular degeneration in the samples from all treated testes obtained three weeks after treatments (Heat only or Heat/TUS): areas with hypospermatogenesis, spermatogenic arrest, vacuolized Sertoli cells, numerous STs with exfoliated GCs, increased degree of GCs apoptosis, and changes in three histomorphometric numeric attributes of STs. We concluded that TUS or TC wraps increase intratesticular temperature of the isolated stallion testes. Further, treatment with TUS or moderate heat may induce mild to moderate degenerative changes in stallion testes. However, to achieve more robust result - severe testicular degeneration, our treatment protocol has to be modified.

Seasonality does not influence cortisol or testosterone production, or seminal quality of stallions located at low latitudes

The effects of seasonality on the reproduction of stallions vary based on the latitude. Although previous studies have shown the influence of seasonality in raw semen quality in south-eastern Brazil, data regarding the influence of seasonality in cooled and frozen stored semen in Brazil is limited. Therefore, in this study, we have analysed if seasonality influences the hormone production (i.e., cortisol and testosterone), spermatogenesis, and quality of fresh, cooled, and frozen semen of stallions in central Brazil, and established the season most suitable for semen cryopreservation in a latitude of 15°S. Ten stallions were followed-up for one year, which was divided into two seasons, namely, drought, and rainy. Fresh, cooled, and frozen-thawed semen samples were assessed using CASA and flow cytometry. Additionally, the temperature and humidity index (THI) was calculated to determine the thermal stress. Although the THI varied between the two seasons, no thermal stress was observed throughout the year, nor were there differences in the physiological parameters of the stallions or plasma cortisol or testosterone levels. Furthermore, differences were not detected in total and progressive motility, sperm capacitation, and sperm membrane integrity, as well as in the number of live sperm with intact acrosomes and high mitochondrial membrane potential, between the two seasons in the fresh and frozen-thawed semen. Our data suggest that semen can be effectively collected and cryopreserved throughout the year within central regions of Brazil.

The stallion sperm acrosome: Considerations from a research and clinical perspective

During the fertilization process, the interaction between the sperm and the oocyte is mediated by a process known as acrosomal exocytosis (AE). Although the role of the sperm acrosome on fertilization has been studied extensively over the last 70 years, little is known about the molecular mechanisms that govern acrosomal function, particularly in species other than mice or humans. Even though subfertility due to acrosomal dysfunction is less common in large animals than in humans, the evaluation of sperm acrosomal function should be considered not only as a complementary but a routine test when individuals are selected for breeding potential. This certainly holds true for stallions, which might display lower levels of fertility in the face of "acceptable" sperm quality parameters determined by conventional sperm assays. Nowadays, the use of high throughput technologies such as flow cytometry or mass spectrometry-based proteomic analysis is commonplace in the research arena. Such techniques can also be implemented in clinical scenarios of males with "idiopathic" subfertility. The current review focuses on the sperm acrosome, with particular emphasis on the stallion. We aim to describe the physiological events that lead to the acrosome formation within the testis, the role of very specific acrosomal proteins during AE, the methods to study the occurrence of AE under in vitro conditions, and the potential use of molecular biology techniques to discover new markers of acrosomal function and subfertility associated with acrosomal dysfunction in stallions.

An Investigation of Equine Sperm Quality Following Cryopreservation at Low Sperm Concentration and Repeated Freeze-Thawing

Stallion spermatozoa are typically cryopreserved at 200 to 300 million sperm/ml; however recent advances such as intracytoplasmic sperm injection (ICSI) requires only one spermatozoon, wasting many, after thawing a whole straw. Cryopreserving at concentrations less than the current standard or refreezing thawed spermatozoa could maximize the use of genetically valuable animals and reduce waste. This investigation aimed to identify if lowering the sperm concentration for cryopreservation affected post-thaw quality after one and two freeze-thaw cycles. Nine ejaculates were collected from three fertile, "good freezer" stallions (post-thaw motility ≥35%) for experiment 1. Each ejaculate was split into eight treatments: five, 10, 20, 50, 100, 200, 300, 400 million sperm/ml and cryopreserved. Post-thaw: motility, viability, acrosome integrity and oxidative stress were assessed. Experiment 2, straws from experiment 1 (300 million sperm/ml) were thawed, diluted to 20 million sperm/ml or left undiluted (control) and refrozen. Post-thaw motility and viability were assessed. In experiment 1 sperm concentration did not affect post-thaw total motility (TM), progressive motility (PM) or viability at 50 to 400 million sperm/ml (P > .05). Whilst sperm concentrations of five to 20 million/ml did differ (post-thaw TM and PM). Both refreezing and reducing spermatozoa concentration, decreased TM, PM and viability (P < .05) after two freeze-thaw cycles. These results suggest cryopreserving at sperm concentrations as low as 50 million/ml maintains spermatozoa quality in good freezer stallions. Spermatozoa maintained some motility and viability when initially cryopreserved at 20 million sperm/ml and after two freeze-thaw cycles but research should investigate more optimal conditions.

Re-stimulation of testicular function in GnRH-vaccinated stallions by daily GnRH agonist treatment

In stallions temporarily not intended for breeding, reversible suppression of testicular function by vaccination against GnRH can be of interest. In the present study, effects of GnRH agonist treatment on the resumption of testicular function after GnRH vaccination were investigated. Testis size, testosterone release, semen characteristics and behavior were evaluated. We hypothesized that GnRH agonist treatment would restore testicular function. Shetland stallions were assigned to an experimental and a control group (n = 6 each). Experimental stallions were GnRH-immunized twice, four weeks apart. Ejaculates for semen analysis and blood for analysis of testosterone concentration and GnRH antibody titers were collected. Each experimental stallion was hemicastrated together with an age-matched control animal when testosterone concentration decreased below 0.3 ng/mL. Three weeks thereafter, daily treatment with the GnRH agonist buserelin was initiated (4 μg/day for 4 weeks followed by 8 μg/day). The remaining testicle was removed when testosterone concentration exceeded 0.5 ng/mL in vaccinated stallions. Time from exposure to a mare until mounting increased in GnRH-vaccinated stallions and decreased with buserelin treatment. Total sperm count decreased after vaccination but increased only slightly in response to buserelin. Sperm motility and percentage of membrane-intact spermatozoa decreased after vaccination and returned to pre-vaccination values with buserelin treatment. Testosterone concentration and testis volume decreased after GnRH vaccination and started to increase with buserelin treatment. In conclusion, the downregulation of testicular function by GnRH vaccination can be counteracted with buserelin. This approach may be useful in GnRH-vaccinated stallions with prolonged suppression of testicular function.

Characterization of sperm cell membrane charge and selection of high-quality sperm using microfluidics in stallions

Intracytoplasmic sperm injection (ICSI) is the only method for in vitro embryo production (IVP) in horses. Besides oocyte developmental competence, the outcome of IVP is also highly dependent on sperm quality. Therefore, it is not only essential to employ superior methods of selecting high quality sperm, but also to be able to characterize which quantifiable properties of sperm quality are most indicative of its fertility. In men, a net negative surface charge, estimated by zeta potential (ZP) is highly correlated with sperm quality and in vitro embryo developmental outcomes. However, there is no information available about approximate charges or ZP in equine sperm. Therefore, in this study we aimed to characterize equine sperm ZP and identify its associations with known measures of sperm quality. Additionally, we aimed to complete a comprehensive comparison of conventional sperm selection techniques as compared to the novel method of microfluidic sorting. Ejaculates (n = 22) were partitioned into fresh (∼23 °C, 0 h; n = 12) and cooled (∼4 °C, 24 h; n = 10) groups, and processed by swim up (SU), density gradient centrifugation (DGC), density gradient-swim up combination (DG-SU), and microfluidic chip (MF) sorting. Motility, progressive motility, cell viability, normal morphology, and ZP were evaluated for both unprocessed fractions and post-selected fractions. The ZP of both fresh and cooled samples was net negative and also correlated with motility and progressive motility for both fresh and cooled samples (P < 0.05). The ZP of cooled samples was also correlated with viability (P < 0.05). Among the compared methods of sperm selection, MF was highly effective in selecting high quality sperm as determined by the measured parameters. Percent motility, progressive motility, normal morphology, and viability of MF selected sperm were of higher quality than sperm selected by SU, and of similar to DG-SU and DGC without the use of potentially harmful centrifugation steps. Correlations between ZP, motility, and viability parameters may indicate a role of external charge on the motility and survival of sperm within the female reproductive tract. In conclusion, we identified an average net negative ZP on equine sperm and correlations between ZP and other measures of sperm quality, as well as having identified MF as a novel effective method of equine sperm selection for IVP.

Genome-wide association study for frozen-thawed sperm motility in stallions across various horse breeds

Objective

The semen quality of stallions including sperm motility is an important target of selection as it has a high level of individual variability. However, effects of the molecular architecture of the genome on the mechanisms of sperm formation and their preservation after thawing have been poorly investigated. Here, we conducted a genome-wide association study (GWAS) for the sperm motility of cryopreserved semen in stallions of various breeds.

Methods

Semen samples were collected from the stallions of 23 horse breeds. The following semen characteristics were examined: progressive motility (PM), progressive motility after freezing (FPM), and the difference between PM and FPM. The respective DNA samples from these stallions were genotyped using Axiom™ Equine Genotyping Array.

Results

We performed a GWAS search for single nucleotide polymorphism (SNP) markers and potential genes related to motility properties of frozen-thawed semen in the stallions of various breeds. As a result of the GWAS analysis, two SNP markers, rs1141327473 and rs1149048772, were identified that were associated with preservation of the frozen-thawed stallion sperm motility, the relevant putative candidate genes being NME8, OR2AP1 and OR6C4. Potential implications of effects of these genes on sperm motility are herein discussed.

Conclusion

The GWAS results enabled us to localize novel SNPs and candidate genes for sperm motility in stallions. Implications of the study for horse breeding and genetics are a better understanding of genomic regions and candidate genes underlying stallion sperm quality, and improvement in horse reproduction and breeding techniques. The identified markers and genes for sperm cryotolerance and the respective genomic regions are promising candidates for further studying the biological processes in the formation and function of the stallion reproductive system.

The efficiency of different types of extenders for semen cooling in stallions

Objective

This study was focused on the influence of the skimmed milk-based extender (SM), the INRA 96 extender and BotuSemen Gold extender on parameters of stallions' ejaculate during storage.

Methods

In this study, 14 stallions between 4 and 20 years of age were monitored. Total and progressive motility, viability and morphology of sperm were evaluated at time intervals of 24, 48 and 72 hours after collection.

Results

The total motility, progressive motility, and values of sperm with normal morphology were significantly higher in the INRA 96 and BotuSemen Gold extenders than in the skimmed milk-based extender (p < 0.01). The sperm viability differed significantly in all extenders (p < 0.01). The highest value of sperm viability was in INRA 96 (64.69 ± 0.67%) and lowest in skimmed milk-based extender (59.70 ± 0.81%). The highest differences occurred at 72 hours of storage. Values of total motility, progressive motility and sperm viability decreased over time (p < 0.01). In case of sperm morphology there was no statistically significant decrease between 48- and 72-hour time intervals.

Conclusion

It can be concluded that the extenders with a chemically defined composition have shown better indicators of insemination capabilities in ejaculates than the skimmed milk-based extender. The BotuSemen Gold extender is a suitable alternative to the INRA 96, when used within 48 hours; after 72 hours of storage, however, the INRA 96 showed a higher share of viable spermatozoa.

Seminal plasma proteins as potential biomarkers for sperm motility and velocities

Seminal plasma proteins have important roles in sperm functionality, and different mechanisms including micro-vesicle transport of proteins are involved in the regulation of sperm biology. Due to the role of seminal plasma, we hypothesized that specific proteins present in seminal plasma may be used as discriminant variables with potential to identify stallions producing different quality ejaculates; 10 fertile stallions, with different motility and velocity values (although within normal ranges) were used in this study. Motilities and velocities were studied using computer assisted sperm analysis (CASA), while protein composition of the seminal plasma was studied using UHPLC-MS/MS. Specific proteins were more abundant in samples with poorer percentages of total motility, average path velocity and circular velocity, and were: Secreted phosphoprotein 1, Fructose-bisphosphate aldolase (p = 1,95E-09; q = 0.0005) and Malate dehydrogenase 1 (p = 1,41E-11; q = 0.002), to the contrary samples with better straight-line velocity values were enriched in Glutathione peroxidase (p=0.00013; q=0.04) and Triosephosphate isomerase (p=0.00015; q=0.04).

The seminal plasma proteins Peptidyl arginine deaminase 2, rRNA adenine N (6)-methyltransferase and KIAA0825 are linked to better motility post thaw in stallions

Seminal plasma plays an important role in sperm physiology. Seminal plasma proteins vehiculated in microvesicles, carry RNAs and proteins with a potential role in early embryo development. Additionally, proteins present in seminal plasma participate in redox regulation and energy metabolism. In view of these facts, we hypothesized that differences in protein composition of the seminal plasma among stallions may help to explain differences in freeze-ability seen among them. Three independent ejaculates from 10 different stallions of varying breeds were frozen using standard protocols in our laboratory. Aliquots of the ejaculate were separated and stored at -80 °C until further proteomic analysis. Semen analysis was performed using computer assisted sperm analysis and flow cytometry. Significant differences in proteome composition of seminal plasma were observed in the group of stallions showing better motility post thaw. 3116 proteins were identified, and of these, 34 were differentially expressed in stallions with better motility post thaw, 4 of them were also differentially expressed in stallions with different percentages of linearly motile sperm post thaw and 1 protein, Midasin, was expressed in stallions showing high circular velocity post thaw. Seminal plasma proteins may play a major role in sperm functionality; being vehiculated through extracellular vesicles and participating in sperm physiology. Bioinformatic analysis identifies discriminant proteins able to predict the outcome of cryopreservation, identifying potential new biomarkers to assess ejaculate quality.

INRA96 Supplemented With Phospholipids Liposomes, A Promising Approach for Stallion Sperm Chilling

Among biotechnologies of reproduction in the equine species, artificial insemination remains the most used technology especially for cooled transported sperm. Although the use of INRA96 extender has demonstrated its efficiency for long-term sperm storage at 4°C or 15°C, some stallions ("bad coolers") are excluded from such technology. Some years ago, we demonstrated that liposomes produced from egg yolk (EY) phospholipids could be an alternative to egg yolk plasma in stallion freezing extenders. To develop a new extender for sperm chilling, we evaluated the protective effect of liposomes produced from EY phospholipids on stallion sperm storage at 4°C. The sperm of stallions from two studs was diluted in INRA96 extender (as control) or an experimental extender (EE) composed of INRA96 supplemented with liposomes of EY phospholipids. After 24H (D1), 72H (D3), and 6 days (D6) or 7 days (D7), motility parameters were evaluated using Computer Assisted Semen Analyzer. Our results demonstrated that total and progressive motility decreased significantly after dilution and storage in INRA96 between D1 and D3 (P < .05) while no significant decrease was observed between D1 and D3 with EE. Regarding VAP parameter, no significant difference was observed between extenders except at D7 in stud 2. Moreover, total and progressive motility were maintained at a significantly higher level (D3, D6, D7) when sperm was stored in EE compared to INRA96. These promising results demonstrate that the supplementation of INRA96 extender with egg-yolk phospholipids liposomes allows a higher protection to stallion sperm cells.

Evaluation of Stallion Testicular Cell Types by Flow Cytometry

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 to determine if flow cytometry procedures could be used to detect differences. For both N and T, percentages of 2n cell types were greater in the Small than Large testes, whereas percentages of 1n cell types in N were greater in the Large than Small testes (P < .05). Testicular cell types in N regions were correlated to similar T regions (r between 0.51 and 0.99; P < .05) in both groups. Flow cytometry and histology scores were correlated in both groups (r between -0.95 and 0.93, P < .05). There were small differences in number of testicular cell types from N and T. With both sample acquisition methods, there was discrimination between the Small and Large testes, therefore, evaluation of testicular cell types using flow cytometry procedures might have clinical applications. Results with comparison of flow cytometry to histology procedures indicate that flow cytometry can be applied clinically to identify changes in testicular cell types of stallions using a needle aspirate.

Climatic factors affecting gestational length in mares under subtropical climate

The aim of this study was (i) to evaluate the relationship of climatic factors with gestational length (GL) and (ii) to evaluate the relationship of sire, foal gender and maternal factors with GL in mares. Retrospective data from 470 gestations of 202 respective mares were collected from a Criollo breeding farm in the southern hemisphere. GL was considered as the interval between ovulation and parturition. Climatic and environmental data (temperature, relative humidity, daily sunshine hours, precipitation, temperature humidity index - THI) were obtained daily and the mean values for foaling month and season were calculated. A multiple factor analysis of variance was performed to determine the relationship of the independent variables and interactions related to the mare, foal gender and stallion, and those related to the weather in each season of the year with GL as the dependent variable. The mean ± standard error (SE) of GL for the 470 gestations was 337 ± 0.4 days with a range of 311-363 days. Young-primiparous mares (340±0.9) had longer gestations (P < .001) than young-multiparous (336 ± 0.7) and mature-multiparous (334 ± 0.7) mares. Foal gender had no effect on GL. Gestational length was found to be affected by the stallion. Mares which experienced an autumn and winter gestational period with less daily sunshine hours had an increased GL (P < .05). In conclusion, environmental and climatic factors during pregnancy influenced the GL in mares, specifically, daily sunshine hours, precipitation and THI presented a negative correlation with GL. Young-primiparous Criollo mares presented longer gestational lengths than young or mature multiparous mares.

Effects of intravenous multiple busulfan injection on suppression of endogenous spermatogenesis in recipient stallion testes

Preparation of recipient stallions is critical step to produce donor spermatogonial stem cell (SSC) derived sperm using transplantation technique. This study was conducted to evaluate the effects of intravenous busulfan infusion on germ cell depletion, semen production, and libido in stallions. Six Thoroughbred stallions were separated into two treatment groups: 1) a multiple low-dose (2.5 mg/kg bw for the first 4 weeks and 5 mg/kg bw for the 5th week); and 2) control group treated with PBS. Testicular samples were obtained at 11 weeks and classified into three different patterns of spermatogenesis, such as normal, Sertoli cell only, and destroyed. Semen collection and libido experiments were performed 1 week before treatment, and 4 and 8 weeks after treatment. For the sperm analysis, total spermatozoa and motility were measured using a light microscope with a motility analyzing system. In the multiple low-dose group, the numbers of tubules categorized as Sertoli cell only were significantly higher than those in the control as well as the total population and total/progressive motility of sperm were significantly decreased 8 weeks after the start of the treatment. The sperm production and motility in the multiple low-dose group appears to be reduced, while libido was maintained. In conclusion, multiple administration of 2.5 mg/kg bw busulfan depletes endogenous germ cells in the stallion recipients for SSC transplantation.

Germ Cell Transplantation in Stallion Testes

The production of donor-derived sperm using spermatogonial stem cell transplantation has been studied in various animals including mice, rats, goats, boar, dogs, sheep, and monkeys. However, germ cell transplantation has not been applied in stallions. The objective of this study was to produce donor germ cell-derived sperm using germ cell transplantation in stallions. Donor germ cells were transplanted into the parenchyma of 3 recipient stallions that had been treated with busulfan IV injections of 15 mg/kg body weight. For the preparation of donor single germ cells, tissue (20 g) from each testis was subjected to a 2-enzyme digestion procedure. Donor testicular germ cells in minimum essential medium α supplemented with 10% fetal bovine serum were transplanted in the testis of recipient stallions at a rate of 2 ml/min. The semen of each recipient stallion was collected using an artificial vagina at 8 weeks after germ cell transplantation. General sperm evaluation and libido tests were performed. Microsatellite fingerprinting with 17 markers was performed to identify the presence of donor-derived sperm in the semen of the recipient stallions. Sperm were observed to have total and progressive motility exceeding 50% throughout the experimental period. The libido of the recipient stallions was unchanged. No donor-derived sperm could be detected in the semen of the recipient stallions by genotyping. In conclusion, the transplantation of donor germ cells into the testicular parenchyma of stallions was not an optimal transplantation technique for producing donor-derived sperm.

Cholesterol-Loaded Cyclodextrin Addition to Skim Milk-Based Extender Enhances Donkey Semen Cooling and Fertility in Horse Mares

The present study aimed to compare semen parameters and fertility of cooled donkey semen extended in a commercially available skim milk (SKM) based extender and the same extender with cholesterol-loaded cyclodextrin (SKM-CLC). In Experiment 1, thirty-five ejaculates from seven jacks were split in SKM and SKM-CLC, extended at 50 million sperm/mL and stored at 5°C for 48 hours. Total motility (TM), progressive motility (PM), percentage of sperm with rapid motility (RAP) were assessed with CASA. Plasma membrane stability (PMS), and high mitochondrial membrane potential (HMP) were assessed with the combination of Yo-Pro and MitoStatusRed with flow cytometry. Semen was assessed before (0), 24 and 48h after cooling. In Experiment 2, two estrous cycles of 15 mares were used for fertility assessment. Mares were examined every other day by transrectal ultrasonography and had ovulation induced with 250 µg of histrelin acetate when a ≥35 mm follicle was first detected. Mares were randomly inseminated with semen obtained from one jack. Semen was extended in either SKM or SKM-CLC and cooled-stored for 24 hours. Pregnancy diagnosis was carried out 15-day post-ovulation. Data were analyzed with a mix model and Tukey's as posthoc and logistic regression model. Significance was set at P ≤ .05. There were no differences in TM, PM, RAP, PMS, and HMP for semen extended in either extender immediately before cooling (P > .05). There was a reduction in TM, PM, RAP, PMS, and HMP overtime across groups (P < .05); however, semen extended with SKM-CLC had superior TM, PM, RAP, PMS, and HMP than semen extended in SKM at 24- and 48-hours post-cooling (P < .05). Mares bred with semen extended in SKM had a lower conception rate (13%, 2/15 cycles) than cycles bred with SKM-CLC (47%, 7/15 cycles; P < .05). In conclusion, incorporating CLC into SKM extender improved cooling ability and fertility of donkey semen in horse mares. It remains to be determined if similar results can be obtained in clinical practice with mares and jennies.

Proteins involved in mitochondrial metabolic functions and fertilization predominate in stallions with better motility

Even in stallions with sperm quality within normal reference ranges at ejaculation, subtle differences in sperm quality exist that in many cases lead to reduced time frames for conservation of the ejaculate and/or reduced fertility. The spermatozoon is a cell highly suitable for proteomics studies, and the use of this technique is allowing rapid advances in the understanding of sperm biology. The aim of the present study was to investigate differences among stallions of variable sperm quality (based on motility and sperm velocities), although all horses had sperm characteristics within normal ranges. The proteome was studied using UHPLC/MS/MS and posterior bioinformatic and enrichment analysis; data are available via ProteomeXchange with identifier PXD025807. Sperm motility, linear motility and circular, straight line and average velocities (VCL, VSL, VAP) were measured using computer assisted sperm analysis (CASA). In stallions showing better percentages of motility, circular and average velocity predominated mitochondrial proteins with roles in the Citric acid cycle, pyruvate metabolism and oxidative phosphorylation. Interestingly, in stallions with better percentages of total motility, sperm proteins were also enriched in proteins within the gene ontology (G0) terms, single fertilization (G0: 0007338), fertilization (G0: 0009566), and zona pellucida receptor complex (GO:0002199). The enrichment of this proteins in samples with better percentages of total motility may offer a molecular explanation for the link between this parameter and fertility. SIGNIFICANCE: Proteomic analysis identified a high degree of specificity of stallion sperm proteins with discriminant power for motility, linear motility, and sperm velocities (VCL, VAP and VSL). These findings may represent an interesting outcome in relation to the molecular biology regulating the movement of the spermatozoa, and the biological meaning of the measurements that computer assisted sperm analysis (CASA) provide. Of a total of 903 proteins identified in stallion spermatozoa, 24 were related to the percentage of total motility in the sample; interestingly, gene ontology (G0) analysis revealed that these proteins were enriched in terms like single fertilization and fertilization, providing a molecular link between motility and fertility. Field studies indicate that the percentage of total motility is the CASA derived parameter with the best correlation with fertility in stallions.

Flow-cytometric analysis of membrane integrity of stallion sperm in the face of agglutination: the "zombie sperm" dilemma

PURPOSE

To define the effect of sperm agglutination, associated with incubation under capacitating conditions, on accuracy of membrane assessment via flow cytometry and to develop methods to mitigate that effect.

METHODS

Sperm motility was measured by CASA. Sperm were stained with PI-PSA or a novel method, LD-PSA, using fixable live/dead stain and cell dissociation treatment, before flow-cytometric analysis. Using LD-PSA, acrosome reaction and plasma membrane status were determined in equine sperm treated with 10 μm A23187 for 10 min, followed by 0, 1, or 2 h incubation in capacitating conditions.

RESULTS

Using PI-PSA, measured membrane integrity (MI; live sperm) was dramatically lower than was total motility (TMOT), indicating spurious results ("zombie sperm"). Sperm aggregates were largely of motile sperm. Loss of motility after A23187 treatment was associated with disaggregation and increased MI. On disaggregation using LD-PSA, MI rose, and MI then corresponded with TMOT. In equine sperm incubated after A23187 treatment, as the percentage of live acrosome-reacted sperm increased, TMOT decreased to near 0.

CONCLUSION

Flow cytometry assesses only individualized sperm; thus, agglutination of viable sperm alters recorded membrane integrity. As viable sperm become immotile, they individualize; therefore, factors that decrease motility, such as A23187, result in increased measured MI. Disaggregation before assessment allows more accurate determination of sperm membrane status; in this case we documented a mismatch between motility and live acrosome-reacted equine sperm that may relate to the poor repeatability of A23187 treatment for equine IVF. These findings are of profound value to future studies on sperm capacitation.

Effects of Spermine and Spermidine supplemented extenders on post-thaw Spermatological Parameters in Stallion Semen Cryopreservation

In this study, the effects of polyamines, Spermine and Spermidine, on long-term preservation and post-thaw spermatological parameters were evaluated. Moreover, determination of the most suitable polyamine and its dose that can be added to standard extenders were aimed. Four adult Arabian stallions were used in the study. Five ejaculates were collected from each of four stallions via artificial vagina two days interval. Each ejaculate was divided into 13 aliquots. INRA96 (95,5%), egg yolk (2%), and glycerol (2,5%) were used as a control extender. Extenders of experimental groups were prepared with different doses of Spermine and Spermidine (0,1 mg/ml; 0,2 mg/ml; 0,4 mg/ml; 1 mg/ml; 2 mg/ml; 4 mg/ml). Stallion semen that were cryopreserved with Control and experimental extenders were evaluated in terms of Total Motility, Progressive Motility, Plasma Membrane Integrity, Capacitation Index, Acrosome Integrity and DNA Fragmentation Index. At the end of the evaluations, it was determined that 0,2 mg/ml Spermine and 0,4 mg/ml Spermidine showed better Total Motility and Progressive Motility, numerically. On the other hand, it was observed that 4 mg/ml Spermine and Spermidine had the lowest statistically significant values (p < 0,001). While statistically similar differences were obtained between groups in terms of the Plasma Membrane and Acrosome Integrity, it was determined that all experimental groups had lower and statistically significant values in terms of Capacitation and DNA Fragmentation Index (p < 0,001). As result, it was observed that the stallion semen cryopreservation success can be increased by the addition of 1-2 mg/ml Spermine that had effective protection on Capacitation and DNA Fragmentation Index without damaging other spermatological properties.

Cryopreservation of Semen from Domestic Livestock: Bovine, Equine, and Porcine Sperm

In modern livestock breeding, cryopreserved semen is routinely used for artificial insemination. Sperm cryopreservation allows for long-term storage of insemination doses and secures reproduction at a desired time point. In order to cryopreserve semen, it needs to be carefully processed to preserve its vital functions after thawing. In this chapter, we describe the processes involved in cryopreservation of bull, stallion, and boar sperm. These include preparation of diluents, dilution of sperm in primary and freezing extender, slow cooling from room temperature to 5 °C, packaging of insemination doses in straws, freezing at a defined cooling rate in liquid nitrogen vapor, cryogenic storage, and thawing. Two-step dilution approaches, with commonly used diluents, are presented, namely, TRIS-egg yolk (TEY) extender for bull sperm, skim milk (INRA-82) extender for stallion sperm, and lactose-egg yolk (LEY) extender for boar sperm. Furthermore, simple methods are presented for cooling and freezing of sperm at defined cooling rates.

Matrix metalloproteinase (MMP)-2, MMP-9, semen quality and sperm longevity in fractionated stallion semen

Matrix metalloproteinase (MMP)-2 and MMP-9 are gelatinases that take part in several reproductive processes. The aim of this study was to measure levels of MMP-2 and MMP-9 in fractionated stallion ejaculates, and to evaluate the association between these components and semen quality, and sperm longevity during cooled storage. Semen quality were assessed separately for sperm-rich fractions (HIGH), sperm-poor fractions (LOW), and whole ejaculate samples (WE) from 33 stallions. After cooled storage with SP either present or removed, sperm motility and DFI were determined. The relative activity of the pro-form of MMP-2, active MMP-2 and total MMP-9 were evaluated using gelatin zymography, and all were present in all fractions of the stallion's ejaculate, with higher relative activity of the latent than active forms and the highest relative activity in the HIGH fraction. The relative activities of MMP-2 and MMP-9 were positively correlated to sperm concentration and total sperm count, but only in the HIGH fraction and not in LOW or WE. The relative activities of MMPs were not related to differences in sperm longevity during cooled storage, measured as sperm motility and DFI. There was a harmful effect of SP on DFI during storage, but this effect was not associated with differences in the relative activities of MMPs. In conclusion, the relative activities of MMPs are not useful as markers for semen quality (other than sperm concentration), or sperm survival during storage in horses.

Hormone Concentrations and Semen Parameters in Criollo Breed Stallions Under Training

The stress associated with training may reduce reproductive efficiency in Criollo stallions. The objective of this study was to compare semen quality and hormone concentrations in Criollo stallions under training or under regular field conditions. Criollo breed stallions (n = 18) were evaluated during the spring. The exercise group (n = 9) performed 1 hour of exercise per day and participated in competitions during the experimental period. The control group (n = 9) neither performed exercise nor participated in competitions. Serum and semen samples were obtained every 15 days (two separate ejaculates an hour apart). Sperm motility, velocity, and morphology were evaluated with a phase-contrast microscope and concentration by a hemocytometer. Diff-Quik stain was used to identify polymorphonuclear cells, and the degree of chromatin condensation was evaluated with the toluidine blue stain. The sperm survival test was performed at a room temperature of 22°C. Semen evaluation was performed in raw samples and in samples diluted in a skim milk and glucose-based extender. Cortisol, testosterone, and estradiol were measured using radioimmunoassay. There was no effect of exercise on testosterone and estradiol concentrations (P = .28 and P = .97, respectively). However, in the exercise group, cortisol concentration was higher after exercise (P = .004). There was an effect of exercise on the following semen parameters: gel-free volume (P < .001), sperm motility (P < .0001), total number of sperm (P = .0001), normal sperm morphology (P < .0001), and total number of morphologically normal and motile sperm (P < .001). No effect of exercise was found in the following semen parameters: color, pH, and sperm concentration. This study showed that exercise had a negative impact on seminal quality; nevertheless, semen parameters were within the normal ranges established for the equine species.

Oxytocin receptor expression in stallion testes and epididymides

Endocrine, paracrine, and autocrine factors orchestrate the development and physiology of the stallion reproductive system. Oxytocin (OXT) is one of the critical endocrine, paracrine, and autocrine factors for the male reproductive system. Previous studies have investigated OXT receptor (OXTR) expression in testes and epididymides, including humans, marmosets, macaques, swine, and sheep. This study aimed to explore (1) OXTR localization in the testes and epididymides and (2) the seasonal modification of OXTR expression in the testes. Adult stallion testis and epididymis samples were prepared using routine castration procedures. Reverse-transcription PCR was performed to detect the presence of OXTR messenger RNA (mRNA) in the testes. Western blot procedure was performed to confirm the cross-reactivity of OXTR antibody to horse OXTR. Immunohistochemistry was performed to detect OXTR protein expression in the testes and epididymides. Oxytocin receptor mRNA was detected in the stallion testes. The OXTR protein band was observed at 55 kDa. Interestingly, the relative intensity of the OXTR protein band varied between nonbreeding and breeding season. The OXTR protein level in the testes collected during the breeding season was higher than that during the nonbreeding season. Oxytocin receptor localization was observed in the cytoplasm of Type A spermatogonia and spermatid. Oxytocin receptor protein expression was also observed in the cytoplasmic area of Leydig cells and the membrane of the seminiferous tubules. The cytoplasm of principal and basal cells in the caput, corpus, and cauda was also immunolabeled with OXTR antibody. In conclusion, based on the expression of OXTR in tissues of testes and epididymides, OXT-OXTR system may be a critical factor for stallion testicular and epididymal function. In addition, according to the seasonal alteration of intensity, the OXT-OXTR system may be associated with seasonal changes in the reproductive system in stallions.

Unusual Penile Prolapse with an Infectious Background Caused by the Burkholderia cepacia Complex in a Stallion

Penile prolapse is a disease manifested by an inability to retract the penis into the preputial sheath. It is reported in a variety of animal species, especially in young and intact males. However, penile prolapse in horses is commonly caused by trauma, sexual activity, pseudohermaphroditism, or neurological deficits, and less often by an infectious background. The present case report aimed to determine the etiological factor of penis infection associated with penile prolapse in a stallion in Poland. Our report indicates that the infectious background of penile prolapse was related to the Burkholderia cepacia complex. Based on antibiotic susceptibility results, the stallion was administered effective streptomycin and enrofloxacin treatment and recovered without complications. The following options are likely to be the infection source: contamination of hay or animal hygiene products. Finally, given its ability to grow in antiseptic solutions, difficulties in culturing, and innate multidrug resistance, this microorganism is currently a challenge to both detection and treatment in veterinary medicine cases.

Effect of season on individual stallion semen characteristics

Horses are long-day seasonal breeding animals, however, with modern stallion reproductive management it is important for collection of semen during periods that are not part of the traditional breeding season. This study was conducted to examine variation in the seminal characteristics of individual stallions in Avila, Spain during 1 year with a particular emphasis on sperm DNA fragmentation. Semen was collected twice per season from a total of 20 stallions. There was a marked seasonal effect on all seminal characteristics, with the greatest on progressive motility, % membrane integrity and least for SDF in the spring months; there was also an interaction effect with respect to individual stallion, indicating that some stallions did not fit this generalised pattern for semen quality. Sperm DNA fragmentation was assessed both immediately after semen collection (T0) and following incubation of extended semen for 24 h (T24) to broadly mimic changes in SDF that might occur in the female reproductive tract. While SDF evaluated at T0 was also generally less in spring, the proportion of stallions with the least SDF values in spring increased from 45% to 60% when assessed at T24, therefore, being consistent with the importance of dynamic SDF assessment in detecting DNA damage that was not detected at T0 or cryptic DNA damage. The results from this study indicate there is individual seasonal variation among stallions in all aspects of seminal characteristics; such variation needs to be considered when prioritising stallions that are to be used for breeding.

The Relationship of Mitochondrial Membrane Potential, Reactive Oxygen Species, Adenosine Triphosphate Content, Sperm Plasma Membrane Integrity, and Kinematic Properties in Warmblood Stallions

Equine sperm possesses a unique physiology because its energy supply is mostly dependent on oxidative phosphorylation of mitochondria as an aerobic source of adenosine triphosphate (ATP) generation. The present study was, therefore, conducted to investigate the relationship between sperm kinematic and functional variables in stallions. Semen samples were collected from five warmblood stallions (three ejaculates from each stallion), diluted with INRA96 and transferred to the laboratory. Next, sperm motility, mitochondrial membrane potential (MMP), production of superoxide anion (as a reactive oxygen species; ROS), ATP content, and plasma membrane integrity were assessed. Motion and functional characteristics differed among investigated stallions (P < .05). In addition, it was revealed MMP was positively correlated with the level of ROS and ATP content and progressive motility (P < .05). The level of ROS was positively correlated with ATP content and negatively correlated with plasma membrane integrity and straightness (P < .05). Adenosine triphosphate content was positively correlated with progressive motility, curvilinear velocity, average path velocity, and beat cross frequency and reversely correlated with plasma membrane integrity and straightness (P < .05). Plasma membrane integrity was positively correlated with straight line velocity, linearity, and straightness and negatively correlated with curvilinear velocity (P < .01). In conclusion, the present study substantiated that kinematic and functional characteristics varied among various warmblood stallions. Furthermore, the present study implicated although higher mitochondrial activity increases ATP synthesis, it leads to elevated superoxide anion production, which could culminate in disintegration of the sperm plasma membrane, thereby altering motion characteristics and swimming pattern of sperm.

Nicotinic Acid (Niacin) Supplementation in Cooling and Freezing Extenders Enhances Stallion Semen Characteristics

In the present study, we aimed to evaluate the possible protective effects of the nicotinic acid (NA) at three concentrations (10, 20, and 40 mM) on the equine cooled and frozen-thawed spermatozoa quality markers including viability, plasma membrane or acrosome integrity, DNA fragmentation, lipid peroxidation, and total oxidant levels. We also evaluated the effects of NA on preservation of the post-thaw sperm quality after 6 hours of cold storage before freezing. Five stallions were used for semen collections. The current experiment was repeated six times using pooled semen samples from two stallions, each time. We showed that NA at 20 and 40 mM concentrations could significantly improve the stallion sperm quality markers during cold storage. However, the protective effects were not different between 20 mM and 40 mM concentrations in most measures. Nicotinic acid could also improve the post-thaw stallion sperm quality at 10, 20, and 40 mM concentrations. However, the 40 mM concentration showed a negative impact on some post-thaw kinematic sperm parameters. Nicotinic acid at 10 and 20 mM concentrations could preserve the sperm cryo-tolerance to be frozen up to 8 hours after collection without a significant decline in most of the post-thaw sperm quality measures. Nicotinic acid could also decrease the level of the lipid peroxidation and total reactive oxygen/nitrogen species in the cooled and frozen-thawed spermatozoa, in a dose-dependent manner. Therefore, NA at 20 mM concentration could preserve most of the stallion sperm quality measures during cold storage (42 hours, 5°C) and enabled storage of cooled stallion semen for 6 hours before freezing without significant deterioration of the post-thaw sperm quality.

Effects of Hemicastration on Testes and Testosterone Concentration in Stallions

The endocrine system is critical to the maintenance of testicular function. The homeostasis of sex hormone levels is orchestrated by positive and negative feedback systems controlled by the hypothalamic-pituitary-gonadal axis. This study investigated the long-term effects of hemicastration on testicular size and function in stallions. Four Thoroughbred stallions, 4-6 years of age, were included in this study. Several parameters, including testicular weight and volume, plasma testosterone concentrations, VASA-positive germ cell populations and cross-sectional areas of the seminiferous tubules were compared in stallions that underwent two hemicastrations, approximately 11 months apart. The weights and volumes of testes harvested at the second hemicastration were significantly higher than those of testes collected at the first hemicastration. However, VASA-positive germ cell populations and the cross-sectional areas of seminiferous tubules were not significantly different between testes harvested at the first and second hemicastrations. Similarly, plasma testosterone concentrations measured weekly for 3 weeks before the first hemicastration, 3 weeks after the first hemicastration, and 3 weeks before the second hemicastration were not significantly different. Our results suggest that hemicastration results in compensatory enlargement of the remaining testis and compensatory steroidogenesis to maintain normal reproductive function in stallions.

A retrospective study on semen quality parameters from four different Dutch horse breeds with different levels of inbreeding

A high degree of inbreeding has been reported to negatively impact semen quality in Friesian horses and Shetland ponies. Both breeds are characterized by a closed studbook, small population size, and high incidence of inbreeding. The Dutch Warmblood studbook (KWPN: Koninklijk Warmblood Paardenstamboek Nederland) is a much larger studbook with two distinct populations: the KWPN-Riding horses, managed as an 'open' studbook, and the KWPN-Harness horses, representing a much smaller subpopulation within the KWPN breed and managed as an 'almost closed' studbook. It was recently reported that the degree of inbreeding in KWPN-Harness horses has increased in recent decades due to the small gene pool; however, the degree of inbreeding is still lower than that of Friesian horses and Shetland ponies. We hypothesized that a high or rising degree of inbreeding might negatively impact semen quality. In the present study, we retrospectively compared semen quality parameters of stallions from four different breeds or types (Friesian Horses, Shetland Ponies, KWPN-Riding horses, and KWPN-Harness horses), each reported with different degrees of inbreeding. Semen concentration, and percentages of motile, morphologically normal and live spermatozoa, and the total number of morphologically normal, progressive motile spermatozoa per ejaculate (TNM) were analyzed for 2832 semen evaluations performed over a 15-year period. KWPN-Harness horses had a significantly lower sperm concentration, % motile spermatozoa and % live spermatozoa than KWPN-Riding horses but the % motile and % morphologically normal spermatozoa and TNM in both KWPN-Harness and KWPN-Riding horses were significantly higher than in Friesian horses and Shetland ponies. These results suggest a lower semen quality in KWPN-Harness than KWPN-Riding horses, potentially as a result of a higher coefficient of inbreeding. The negative trend observed in the KWPN-Harness horses may be a warning sign, and breeders or stud books should monitor the degree of inbreeding carefully to avoid a further reduction in semen quality, to the levels observed in Friesian horses and Shetland ponies.

Direct contact may affect the efficacy of stallion exposure in hastening the onset of cyclicity in anestrous mares

Introducing males to seasonally anestrous females has been shown to increase LH concentrations and hasten the first ovulation in ewes and goat does. Investigation of this sociosexual phenomenon in mares has not been well studied. The objective of this study was to determine if direct or indirect exposure of anestrous mares to a stallion would result in a similar increase in LH and hasten the first ovulation. In late February, mares were stratified by parity and age and assigned randomly to three treatments (n = 7/treatment): (1) DXP (direct exposure; mares housed adjacent to stallion and allowed direct contact for 2 h for 3 d/wk by placing the stallion into a cage in the center of a tease pen); (2) IXP (indirect exposure; mares housed in an adjacent pen to the stallion but not allowed direct contact); and (3) CON (control; mares housed away from stallion and not allowed direct or indirect exposure). During the first, third, and fifth treatment days, blood was collected hourly for 8 h beginning just before treatment initiation for measurement of LH and prolactin (PRL) concentrations. Hormone concentrations were analyzed as repeated measures and time from the first day of treatment to ovulation was analyzed using one-way ANOVA. Interval from treatment initiation to first ovulation did not differ (P > 0.05) among treatments: 36.3 ± 6.7, 42.8 ± 4.2, and 48.3 ± 4.2 d for DXP, IXP, and CON, respectively. When comparing the mares based on social status within treatment and level of direct interaction with the stallion, socially dominant DXP mares ovulated sooner (P < 0.05) than socially subordinate DXP mares (23.8 ± 3.2 and 53.0 ± 6.8 d, respectively). Although LH concentrations did not differ (P > 0.05) among treatments, a significant (P < 0.05) day effect was detected with concentrations being greater on the fifth treatment day compared with the first and third days. Concentrations of PRL were greater (P < 0.05) in IXP compared with DXP and CON, regardless of treatment day. Regardless of treatment, PRL concentrations were greater (P < 0.05) on the third treatment day, compared with the first and fifth days. We conclude that exposure of anestrous mares to a stallion, whether direct or indirect, to anestrous mares failed to elicit the same effects that have been observed in short-day breeders. The effect of stallion exposure on the onset of cyclicity in anestrous mares may be dependent on the duration of direct contact.

Effects of cashew gum and nanoparticles on cooled stallion semen

BACKGROUND

Cryopreservation of stallion spermatozoa tends to cause plasma membrane damage due to the low ratio of cholesterol to phospholipids. Gums have been suggested as an alternative cryoprotectant to glycerol for stallion spermatozoa. Therefore, the present experiment was designed to verify whether the effect of addition of cashew gum (CG), or nanoparticles (NP) containing CG, to the extender before cooling on sperm quality in stallion semen. Ejaculates from 6 stallions were extended and split between six treatment groups (control, a-tocopherol [TOC], CG1, CG0.5, NP1 and NP0.5), stored in cryotubes at 4 °C.

RESULTS

Aliquots were analysed by computer-assisted sperm motility analysis on the day of collection, and after 24 h and 48 h of cold storage. After 48 h, the total motility with NP1 (78.53 + 6.31%) was similar to control 85.79 + 6.31% at 0 h. The same pattern was observed for progressive motility. Membrane integrity assessed by flow cytometer was similar between control, TOC and G1 at all storage times. The DNA fragmentation in the control group increased at all time points, whereas chromatin integrity was maintained after 24 h in TOC and NP0.5 compared to 0 h. There was no increase in the proportion of live spermatozoa producing hydrogen peroxide, but there was a tendency for an increased proportion of spermatozoa in the live superoxide category in CG1 after 24 h cooled storage.

CONCLUSIONS

The addition of CG or CG-derived NP to extender for stallion semen was not harmful to the sperm cells.

High-throughput sperm assay using label-free microscopy: morphometric comparison between different sperm structures of boar and stallion spermatozoa

The capacity for microscopic evaluation of sperm is useful for assisted reproductive technologies (ART), because this can allow for specific selection of sperm cells for in vitro fertilization (IVF). The objective of this study was to analyze the same sperm samples using two high-resolution methods: spatial light interference microscopy (SLIM) and atomic force microscopy (AFM) to determine if with one method there was more timely and different information obtained than the other. To address this objective, there was evaluation of sperm populations from boars and stallions. To the best of our knowledge, this is the first reported comparison when using AFM and high-sensitivity interferometric microscopy (such as SLIM) to evaluate spermatozoa. Results indicate that with the use of SLIM microscopy there is similar nanoscale sensitivity as with use of AFM while there is approximately 1,000 times greater throughput with use of SLIM. With SLIM, there is also allowace for the measurement of the dry mass (non-aqueous content) of spermatozoa, which may be a new label-free marker for sperm viability. In the second part of this study, there was analysis of two sperm populations. There were interesting correlations between the different compartments of the sperm and the dry mass in both boars and stallions. Furthermore, there was a correlation between the dry mass of the sperm head and the length and width of the acrosome in both boars and stallions. This correlation is positive in boars while it is negative in stallions.

Effect of Caffeine and Pentoxifylline Added Before or After Cooling on Sperm Characteristics of Stallion Sperm

Different additives have been tested in cooled stallion sperm, in order to maintain sperm quality and to ameliorate the decrease in sperm fertility potential. In several species, caffeine and pentoxifylline promote sperm motility by increasing energy production. We evaluate the effects of caffeine and pentoxifylline when added to stallion sperm before or after cooling. Three ejaculates from five stallions each were processed and resuspended in skim milk extender. Caffeine (5 mM), pentoxifylline (3.5 mM), or both additives combined were included to sperm before or after cooling (4°C for 24 hours). Cooled sperm were incubated at 37°C and evaluated at 0, 30, 60, and 120 minutes for motility, morphology, viability (flow cytometry), and membrane functionality (hypo-osmotic swelling test). Results were analyzed by two-factor mixed model for repeated measures and Tukey comparisons. As main effects, the caffeine and pentoxifylline affected significantly motility and kinematic parameters, without interaction between treatment and incubation after cooling. No differences were observed whether the additives were added prior or after cooling. Pentoxifylline added after cooling reduced significantly motility during incubation, but with higher values at 30 minutes. We detected a decrease in morphologically normal sperm (P < .0001), caused by an increase of tail defects (P < .003) in the presence of both additives. Viability and membrane functionality were also significantly impaired by additives. Pentoxifylline when added after cooling improved sperm motility and kinematic parameters for a short period of time. However, sperm characteristic related to fertility potential was compromised after a prolonged exposure to caffeine or pentoxifylline.

Motility and Fertility Evaluation of Thawed Frozen Stallion Semen After 24 Hours of Cooled Storage

Breeding mares with cryopreserved semen requires specialized equipment for storage and thawing and more intensive mare management. The objectives of this study were (1) evaluate the longevity of frozen stallion semen once it had been thawed, extended, and maintained at 5°C for 48 hours in a passive cooling container, and (2) determine fertility potential of frozen semen that had been thawed, extended, and used to inseminate mares after 24 hours of cooled storage. Eight ejaculates were collected and aliquots were cooled in either INRA96 and CryoMax LE minus cryoprotectant at a concentration of 50 million total sperm/mL. The remainder of the ejaculate was frozen in CryoMax LE extender at a concentration of 200 million total sperm/mL. Semen was thawed using 1 of 3 thawing protocols, and diluted to a concentration of 50 million total sperm/mL in either INRA96 or CryoMax LE minus cryoprotectant and cooled to 5°C. Sperm motility was evaluated at 24 and 48 hours. Eight mares were inseminated over two estrous cycles using frozen semen that had been thawed, extended in INRA96, and cooled for 24 hours. There was no difference in progressive motility at 24 or 48 hours of cooled-storage post-thaw between the 3 thawing protocols. An overall per cycle pregnancy rate of 56% (9/16 cycles) was achieved using frozen-thawed semen that had been extended and cooled for 24 hours. In summary, frozen stallion sperm was thawed, extended, and cooled to 5°C for 24 hours and still maintained adequate (>30%) sperm motility and fertility.

Seasonal variations in sperm DNA fragmentation and pregnancy rates obtained after artificial insemination with cooled-stored stallion sperm throughout the breeding season (spring and summer)

The aim of this study was to assess seasonal variations during different periods of the breeding season (spring and summer) on stallion sperm DNA fragmentation and in vivo fertility associated with cooled-stored semen samples. Ejaculates were collected from eleven stallions and assessed for sperm motility (assessed by computer-assisted sperm analysis) and plasma membrane integrity (evaluated under fluorescence microscopy). Sperm DNA fragmentation (evaluated by the Sperm Chromatin Dispersion test) was assessed in cooled-stored semen at 5 °C for up to 24 h. Artificial insemination was performed throughout the breeding season. Mares were inseminated with cooled-stored semen (up to 24 h) every other day until ovulation. Pregnancy rates per cycle were determined detecting the embryonic vesicle by ultrasonography fifteen days after ovulation. Values (mean ± SD) for progressive sperm motility were significantly higher (P < 0.05) in spring (53.57 ± 9.97%) in comparison to summer (41.37 ± 10.81%). No significant differences in plasma membrane integrity were found between seasons (P > 0.05). Sperm DNA fragmentation was significantly lower (P < 0.01) in spring in comparison to summer after 0h (4.81 ± 1.87% vs. 8.77 ± 5.78%), 6h (9.00 ± 3.19% vs. 18.73 ± 8.22%) and 24h (14.6 ± 4.13% vs. 30.14 ± 9.85%) of cooled-storage. Pregnancy rates per cycle were also significantly higher (P < 0.01) in spring (50%) in comparison to summer (37%). There was a moderate negative relationship between positive pregnancies and sperm with fragmented DNA (r = - 0.619; P < 0.001). Semen samples associated with moderate fertility levels (Pregnancy rate < 50%) showed a higher percentage of sperm with fragmented DNA compared to samples obtaining higher fertility levels. In conclusion, seasonal variations were found during the breeding season, obtaining lower sperm DNA fragmentation and higher pregnancy rates in spring. Additionally, samples with the highest proportion of sperm with fragmented DNA showed the lowest fertility levels throughout the breeding season.

Endoscopic Laser Ablation of a Midline Cyst of the Colliculus Seminalis as a Treatment for Anejaculation in a Stallion

An 18-year-old Appaloosa stallion presented with a history of ejaculatory dysfunction, which had recently progressed to an inability to ejaculate (anejaculation). Transrectal ultrasound evaluation revealed the presence of a prominent midline cyst of the colliculus seminalis, which was compressing the most terminal parts of the deferent ducts. Both ducts were enlarged and filled with hyperechoic content. The stallion was diagnosed with a complete occlusion of the deferent ducts because of the compression from the midline cyst of the colliculus seminalis. To date, there are no established treatments for this condition in stallions, although several procedures have been successfully used in men affected by similar problems. Therefore, we proposed performing one of these procedures-a laser ablation of the cyst to collapse it and to open the ejaculatory path. The stallion was placed under general anesthesia, and an endoscopic ultrasound-guided laser ablation of the cyst was performed. No immediate or long-term complications were observed. After the expulsion of accumulated material, the stallion produced normal semen and successfully impregnated mares during the next breeding season.

Does Coenzyme Q10 Exert Antioxidant Effect on Frozen Equine Sperm?

During semen cryopreservation, the sensitivity of equine sperm to oxidative stress is increased by the eliminated seminal plasma. Thus, antioxidant addition to the semen extender can be helpful to the sperm survival after freezing and thawing. This work aimed to test whether coenzyme Q10 (CoQ10) added in different concentrations to the INRA 82 freezing extender has antioxidant function on equine sperm to improve its fertilizing ability. Semen samples from five stallions were frozen with the extenders: (T1) INRA 82, control, (T2) T1+ 5 μM CoQ10, (T3) T1+ 25 μM CoQ10, and (T4) T1+ 50 μM CoQ10. After sample thawing, sperm motility and kinetics characteristics were evaluated using a computer-assisted sperm analysis and sperm membrane functionality and integrity were evaluated with a hypo-osmotic swelling test and an epifluorescence microscopy, respectively. The nitrite (NO₂^-) and hydrogen peroxide (H₂O₂) concentrations of the semen samples were measured with spectrophotometry. There was no difference on the sperm characteristics among all treatments (P > .05). However, the 25 μM CoQ10 (T3) decreased NO₂^- concentration (6.7 ± 2.2 μM/μg protein) compared with the treatments T1, T2, and T4 (64.3 ± 3.7, 59.4 ± 5.3, 45.1 ± 8.6 μM/μg protein), respectively, as well H₂O₂ concentration (1.8 ± 0.3 μM/μg protein) compared with the control (4.6 ± 0.4 μM/μg protein) and 5 μM CoQ10 treatments (4.8 ± 0.2 μM/μg protein, P < .05). In conclusion, 25 μM CoQ10 plays a significant role as antioxidant to the frozen equine sperm, decreasing NO₂^- and H₂O₂ concentrations. Thus, its addition to the INRA 82 freezing extender may be beneficial to the fertilizing ability of equine semen.

Season does not have a deleterious effect on proportions of stallion seminal plasma proteins

The mechanism by which the content of the major groups of seminal plasma proteins in stallion semen changes between the breeding and non-breeding seasons remains unknown. Here, we investigated the proportions of non-heparin-binding, phosphorylcholine-binding, and heparin-binding proteins in seminal plasma with the aim of relating them to sperm quality and testosterone levels in good and bad freezer stallions. Only minor variations in the major protein groups were found between the breeding and non-breeding seasons. In the non-breeding season, a higher content of a subset of non-heparin binding proteins as well as of heparin-binding proteins was found. Analysis of semen characteristics revealed a somewhat contrasting picture. While only minor variations in sperm kinematics and sperm morphology were found between seasons, the flow-cytometric measurements of mitochondrial membrane potential and also, to some extent, reactive oxygen species production indicated lower sperm quality in the breeding season. Chromatin integrity and testosterone levels were unchanged between seasons. The results suggest that stallion ejaculates could be used year-round for freezing, since only minor differences in protein composition exist between the breeding and non-breeding seasons, as well as between good and bad freezers. In addition, sperm quality is not impaired during the non-breeding season.

Genetic and Environmental Factors Influencing Gestation Length in Lusitano Horses

Breeding and parturition records collected over a period of 35 years in the Alter Real stud of Lusitano horses were used to calculate gestation length (GL). The 1027 gestations by 209 mares mated to 60 stallions had a mean GL of 338.1 ± 9.26 days. The mixed model analysis of variance indicated that the sex of the foal and inbreeding of the dam and foal had no significant effect on GL (P > .05). On the other hand, GL increased linearly with mare age, with an estimated regression coefficient of 0.155 ± 0.069 days/year (P < .05). Year and conception month affected GL (P < .05), with longer gestations observed when breeding occurred between January and April, followed by a decline of about 5 and 10 days in GL of mares bred in May and in June-July, respectively. Important differences were observed between stallions (P < .05), with most stallions resulting in a distribution of GL in an interval of ±5 days. The inclusion of the mare as a random effect in the mixed model resulted in an estimated repeatability of GL of 0.427, indicating that mares tend to be regular in having long or short gestations across their lifetime. Variance components estimated in an Animal Model resulted in heritability estimates of 0.39 for maternal genetic effects and 0.19 for direct genetic effects, with no association between the two components. Overall, the mare seems to have the major genetic influence on GL in Lusitano horses, but environmental factors, such as month of conception and also the age of the mare, have a noticeable effect.

Stallion Sperm Integrity After Centrifugation to Reduce Seminal Plasma Concentration and Cool Storage for 4 days

The objective of the study was to investigate if reducing the seminal plasma of stallion extended semen by centrifugation once will suffice to maintain acceptable semen quality for insemination after 4 days of cool storage. Collected semen was extended to 25 × 10⁶ sperm/mL and subjected to one of the following treatments: noncentrifuged (control), centrifuged for 10 minutes at 900 × g and 1800 × g. The supernatant was partially removed, and the sperm pellet, reconstituted and re-extended. It was then placed in a passive cooling device overnight and then transferred to a refrigerator for the remainder of the cooling period. At day 0, 2, and 4, total motility (TM), progressive motility (PM), and plasma (PLM) and acrosomal membrane integrity were assessed. Centrifuged groups had higher TM and PM at day 4 than the control group (P < .05). Likewise, centrifuged groups had higher intact PLM in day 4 (P < .05). A single centrifugation cycle to reduce seminal plasma concentration will suffice to preserve sperm integrity acceptable for an artificial insemination dose up to 4 days of cool storage.

Ejaculated compared with epididymal stallion sperm vitrification

The aim of this study was to evaluate the effect of trehalose and lactose extenders on ejaculated and epididymal stallion sperm vitrification. Ejaculated semen samples were collected from seven fertile stallions, and cauda epididymis samples were collected from ten stallion carcasses after slaughter. Both the ejaculated and the epididymis samples were diluted and vitrified using INRA 96® and bovine serum albumin as well as trehalose or lactose. As a control, ejaculated and epididymal samples were collected and frozen using the conventional method. Vitrification was performed by immersing sperm suspensions directly in LN2. After thawing or devitrification, there was assessment of samples for sperm motility using computer-assisted analysis. Viability was assessed using SYBR-14 and propidium iodide (PI) and acrosome integrity by fluorescein using isothiocyanate combined with peanut agglutinin (FITC-PNA) and PI. Epididymal sperm vitrification with trehalose (EPT) or lactose (EPL) resulted in greater progressive sperm motility than sperm of the control sample (EPC). After post-thaw/devitrification of sperm in the EPT group, sperm motility was greater (P<0.001) compared to that using EPL (50.72 ± 5.09% compared with 34.21 ± 3.02%). The results from assessment of ejaculated sperm samples after undergoing the vitrification process indicated cells were less viable (P<0.001) than the control (EJC) sample. In conclusion, vitrification of epididymal stallion sperm using trehalose might be a beneficial alternative for the long-term storage of sperm samples with great economic value. Spermatozoa from vitrified ejaculates of stallions, however, had lesser motility and viability rates than samples subjected to conventional freezing.