Horse Sperm Research Articles

Comparative Study on the Sperm Proteomes of Horses and Donkeys.

The reproductive performance of horse sperm and donkey sperm has been reported to differ. Sperm proteins play a crucial role in sperm viability and fertility. Although differences between species are known, no prior study has investigated disparities in the sperm proteome between horses and donkeys. Therefore, this study characterized and compared the sperm proteomes of horses and donkeys using 4D-DIA mass spectrometry technology. We identified 3436 proteins in horse sperm and 3404 proteins in donkey sperm. Of these, 3363 proteins were expressed in both horse and donkey sperm, with 73 proteins being specifically expressed in horse sperm, and 41 in donkey sperm. According to data analysis, donkeys exhibited a greater percentage of motility and progressive movement in straight-line sperm than horses, as well as lower percentages of static and slow sperm than horses. Joint analysis of the results from the horse and donkey sperm proteomes and their CEROS II-read parameters demonstrated a possible association between sperm proteins and their sperm viability patterns. These findings suggest that there are discrepancies in the expression levels and protein compositions of horse and donkey sperm and that certain specific proteins may be responsible for the differences in performance between these two species.

L-carnitine enhances the kinematics and protects the sperm membranes of chilled and frozen-thawed Peruvian Paso horse spermatozoa

l-carnitine (LC) transports fatty acids to the mitochondria for energy production, reducing lipid availability for peroxidation through β-oxidation. This research examines the effect of LC supplementation to two skimmed milk-based extenders on the cryosurvival of chilled (5°C) and frozen-thawed Peruvian Paso horse spermatozoa .An initial experiment determined the optimal LC concentration (0, 1, 5, 10, 25, and 50 mM) when added to INRA-96® and UHT (skimmed milk + 6% egg yolk) extenders, using nine ejaculates from three stallions chilled for up to 96 h. Subsequently, the effect of 25 mM LC supplementation (the optimal concentration) on chilling (INRA-96) and freezing (INRA-Freeze®) extenders was evaluated using eight pooled samples from sixteen ejaculates (2 ejaculates/pool) from four stallions. Results indicated that all LC concentrations produced significantly higher values (P<0.05) for kinematic variables (total [TM] and progressive motilities, curvilinear [VCL] and straight-line [VSL] velocity, and beat-cross frequency [BCF]), and the integrity of plasma/acrosome membranes (IPIA) compared to non-supplemented chilled sperm samples for up to 96 h with both extenders. Moreover, the use of 25 mM LC was more efficient (P<0.05) in preserving the post-chilled values of velocity, BCF, and IPIA for the long term than lower LC concentrations (1–10 mM). Post-thaw values of total motility, the amplitude of lateral head displacement (ALH), and IPIA were significantly improved (P<0.05) when INRA-Freeze extender was supplemented with 25 mM LC. In conclusion, supplementation of l-carnitine to skimmed milk-based extenders enhanced kinematic variables and protected the membrane integrity in chilled and frozen-thawed Peruvian Paso horse spermatozoa.

Impact of Seminal Plasma Antioxidants on DNA Fragmentation and Lipid Peroxidation of Frozen-Thawed Horse Sperm.

Cryopreservation is a stressful process for sperm, as it is associated with an increased production of reactive oxygen species (ROS). Elevated ROS levels, which create an imbalance with antioxidant capacity, may result in membrane lipid peroxidation (LPO), protein damage and DNA fragmentation. This study aimed to determine whether the membrane LPO and DNA fragmentation of frozen-thawed horse sperm relies upon antioxidant activity, including enzymes (superoxide dismutase (SOD), glutathione peroxidase (GPX), catalase (CAT) and paraoxonase type 1 (PON1)); non-enzymatic antioxidant capacity (Trolox-equivalent antioxidant capacity (TEAC), plasma ferric reducing antioxidant capacity (FRAP) and cupric reducing antioxidant capacity (CUPRAC)); and the oxidative stress index (OSI) of their seminal plasma (SP). Based on total motility and plasma membrane integrity (SYBR14+/PI-) after thawing, ejaculates were hierarchically (p < 0.001) clustered into two groups of good- (GFEs) and poor-(PFEs) freezability ejaculates. LPO and DNA fragmentation (global DNA breaks) were higher (p < 0.05) in the PFE group than in the GFE group, with LPO and DNA fragmentation (global DNA breaks) after thawing showing a positive relationship (p < 0.05) with SP OSI levels and ROS production. In addition, sperm motility and membrane integrity after thawing were negatively (p < 0.05) correlated with the activity levels of SP antioxidants (PON1 and TEAC). The present results indicate that LPO and DNA fragmentation in frozen-thawed horse sperm vary between ejaculates. These differences could result from variations in the activity of antioxidants (PON1 and TEAC) and the balance between the oxidant and antioxidant components present in the SP.

Comparison of the metabolite profile of donkey and horse seminal plasma and its relationship with sperm viability and motility

Previous research revealed that several seminal plasma (SP) metabolites are related to sperm functionality, fertility, and preservation. While it is understood that variations between species exist, whether the SP metabolome differs between donkeys and horses has not been previously investigated. The aim of this work, therefore, was to characterize and compare donkey and horse SP metabolites using nuclear magnetic resonance (NMR) spectroscopy, and relate them to sperm viability and motility. For this purpose, ejaculates from 18 different donkeys and 18 different horses were collected and separated into two aliquots: one for harvesting the SP by centrifugation and obtaining the metabolic profile through NMR, and the other for evaluating sperm viability and motility. Based on total motility and sperm viability, samples were classified as with good (GQ) or poor (PQ) quality. The metabolomic profile of donkey and horse SP revealed the presence of 28 metabolites, which coincided in the two species. Yet, differences between horses and donkeys were observed in the concentration of 18 of these 28 metabolites, as well as between ejaculates classified as GQ or PQ and in the relationship of metabolites with sperm motility and viability. These findings suggest that sperm from donkeys and horses differ in their metabolism and energetic requirements, and that the concentration of specific SP metabolites may be related to sperm functionality. Further research should shed light on the metabolic needs of donkey and horse sperm, and evaluate how the knowledge collected from the contribution of these metabolites can help improve semen preservation in the two species.

Assessment of methods to activate epididymal sperm motility

Horse epididymal sperm has satisfactory motility activation (Mot-Act) after harvesting and cryopreservation; however, donkeys typically display poor Mot-Act despite high-plasma-membrane integrity (PMI) with high-mitochondrial-membrane-potential (ΔΨM). Mot-Act can be achieved in murine epididymal sperm with centrifugation by removal of sperm-bound seminal plasma (SP) proteins; also, in other mammals, the dilution of epididymal sperm with SP promotes Mot-Act. Dilution of cryopreserved sperm with an extender without cryoprotectants aids Mot-Act in other species. It is possible that all these methods can enhance donkey and horse epididymal Mot-Act and that there might be positive interactions between methods; however, these hypotheses have yet to be tested. Single-layer colloid-centrifugation (SLC) is a powerful tool to remove sperm-bound particles. Thus, this study sought to assess methods and potential interactions to promote Mot-Act in epididymal sperm by comparing an equid with satisfactory Mot-Act (i.e., the horse) with another poor Mot-Act (i.e., the donkey). Mot-Act, PMI, and ΔΨM were assessed by submitting horse and donkey cryopreserved sperm to re-extension (1:3) on the same egg-yolk extender used for cryopreservation (BC), also the same extender lacking CPA, and donkey- and horse-SP. The Mot-Act, PMI, and ΔΨM were carried out 10-, 30-, and 60-min after incubation. Results showed that donkey and horse epididymal sperm had lower Mot-Act, PMI, and ΔΨM when dilutedwith donkey- and horse-SP (P<0.05). Conversely, Mot-Act was similar between horse-SP, BC, and CPA (P>0.05), and it all increased after 10 min of incubation (P<0.05). PMI and ΔΨM were not different across groups in horse epididymal sperm (P>0.05). Then the same processing methods were applied before and after SLC for cryopreserved horse and donkey epididymal sperm, and then Mot-Act, PMI, and ΔΨM were assessed. The results showed that donkey epididymal sperm had higher Mot-Act when diluted in the same egg-yolk extender compared to donkey-SP or CPA (P<0.05); Horse epididymal sperm had lower PMI and ΔΨM when diluted in donkey-SP compared to BC and horse-SP (P<0.05). The sperm recovery after SLC was similar between donkey and horse epididymal sperm (P>0.05). Next, zona-pellucida binding was carried out as an in vitro functional assessment of Mot-Act, as it is necessary for fertilization. Dilution with SP from either species' sperm did not enhance zona-pellucida binding (P>0.05) as it does for other mammals. Previously, it was suggested that donkey sperm does not bind to heterologous zona-pellucida (i.e., bovine); however, herein, it did bind similarly to horse sperm (P<0.05). This study is a foundation to expand the knowledge in equine sperm biology, showing that donkey epididymal sperm can have Mot-Act enhanced using re-extension with BC, and other standard methods cannot. Also, this is the first report to demonstrate that donkey sperm binds to heterologous zona-pellucida.

The Autophagy Marker LC3 Is Processed during the Sperm Capacitation and the Acrosome Reaction and Translocates to the Acrosome Where It Colocalizes with the Acrosomal Membranes in Horse Spermatozoa

Despite its importance in somatic cells and during spermatogenesis, little is known about the role that autophagy may play in ejaculated spermatozoa. Our aim was to investigate whether the molecular components of autophagy, such as microtubule-associated protein 1 light chain 3 (LC3), are activated in stallion spermatozoa during the capacitation and acrosome reaction and if this activation could modulate these biological processes. To analyze the autophagy turnover, LC3I and LC3II proteins were assessed by western blotting, and the ratio between both proteins (LC3II/LC3I) was calculated. In somatic cells, this ratio indicates that autophagy has been activated and similar LC3 processing has been described in mammalian spermatozoa. The subcellular localization of autophagy-related proteins was assessed by immunofluorescence with specific antibodies that recognized Atg16, Beclin-1, and LC3. The colocalization of acrosomal membranes (PNA) and LC3 was studied by confocal microcopy, and the acrosome reacted cells were quantified by flow cytometry. The incubation of stallion sperm in capacitating conditions (BWW; 3 h) significantly increased LC3 processing. This increment was three to four times higher after the induction of the acrosome reaction in these cells. LC3 was mainly expressed in the head in mature ejaculated sperm showing a clear redistribution from the post-acrosomal region to the acrosome upon the incubation of sperm in capacitating conditions (BWW, 3 h). After the induction of the acrosome reaction, LC3 colocalized with the acrosome or the apical plasmalemma membranes in the head of the stallion spermatozoa. The inhibition or activation of autophagy-related pathways in the presence of autophagy activators (STF-62247) or inhibitors (E-64d, chloroquine) significantly increased LC3 processing and increased the percent of acrosome reacted cells, whereas 3-methyladenine almost completely inhibited LC3 processing and the acrosome reaction. In conclusion, we found that sperm capacitation and acrosome reaction could be regulated by autophagy components in sperm cells ex vivo by processes that might be independent of the intraluminal pH of the acrosome and dependent of LC3 lipidation. It can be speculated that, in stallion sperm, a form of noncanonical autophagy utilizes some components of autophagy machinery to facilitate the acrosome reaction.

ProAKAP4 Concentration Is Related to Sperm Motility and Motile Sperm Subpopulations in Frozen-Thawed Horse Semen.

ProAKAP4 is the precursor of AKAP4 (A-kinase Anchor protein 4), the main structural protein of the fibrous sheath of sperm. The amount of proAKAP4 reflects the ability of spermatozoa to maintain the flagellum activity and functionality up to the site of fertilization and is positively correlated with progressive motility in several mammalian species. The aim of this study was to investigate the relationship between proAKAP4 concentration with horse sperm motility descriptors and spermatic motile subpopulations. For this purpose, a total of 48 ejaculates from 13 different stallions were analyzed. Spermatic motility descriptors were obtained by the CASA system, and four motile subpopulations (SP) with specific motility patterns were statistically identified. ProAKAP4 concentrations were evaluated by ELISA. The relationship between motility descriptors of sperm subpopulations and proAKAP4 concentrations was evaluated. Following a hierarchical cluster statistical analysis, ejaculates were divided into two groups according to their proAKAP4 concentrations, either having low proAKAP4 concentrations (5.06−35.61 ng/10M spz; n = 23) or high (39.92−82.23 ng/10M spz; n = 25) proAKAP4 concentrations (p < 0.001). ProAKAP4 concentrations were positively correlated (p < 0.05) with total and progressive motility, as well as with parameters of velocity. ProAKAP4 amount also showed a negative correlation (p < 0.05) with sperm motile subpopulation number 3, which was the subpopulation with the lowest velocity parameters. In conclusion, proAKAP4 concentration in stallion semen positively reflects sperm progressive motility with the functional velocity kinematic descriptors. Concentrations of proAKAP4 higher than 37.77 ng/10M spz were correlated with a very good quality frozen/thawed stallion semen.

Effect of Melatonin and Caffeine Supplementation to Freezing Medium on Cryosurvival of Peruvian Paso Horse Sperm Using a Two-Step Accelerating Cooling Rate.

This research examined the antioxidant and cryoprotective effects of melatonin (ME) and caffeine (CAF) supplementation in freezing medium on the cryosurvival of Peruvian Paso horse sperm using a two-step accelerating cooling rate. Twenty ejaculates from four adult and fertile stallions were recovered, initially diluted with INRA-96®, and finally frozen with INRA-Freeze® with either no supplementation (as control), 1 μM ME, or 2 mM CAF using a two-ramp freezing system content inside a cryogenic-box and liquid nitrogen vapors. The sperm kinematic parameters and integrity of the plasma and acrosomal membranes of fresh semen and cryopreserved samples were evaluated using the CASA system (SCA-Evolution® 2018) and PI/fluorescein isothiocyanate-conjugated peanut (Arachis hypogaea) agglutinin double fluorescent test, respectively. The oxidative stress of post-thaw sperm samples was also assessed using the CellRox Deep Red fluorescence test. The results showed that curvilinear velocity and average-path velocity were greater (p < 0.05) after freezing with CAF than the control group. In addition, there were significance differences (p < 0.01) between stallions (1-4) in post-thaw kinematic parameters regardless of ME or CAF addition. Both ME and CAF improved (p < 0.05) the proportion of sperm with intact plasma membranes and intact acrosomes. Nevertheless, neither CAF nor ME improved the oxidative stress after the cryopreservation process.

Seminal Plasma Antioxidants Are Related to Sperm Cryotolerance in the Horse.

The objective of this study was to determine the relationship of enzymatic (superoxide dismutase, SOD; glutathione peroxidase, GPX; catalase, CAT; and paraoxonase type 1, PON1) and non-enzymatic antioxidants (measured in terms of: Trolox equivalent antioxidant capacity, TEAC; cupric-reducing antioxidant capacity, CUPRAC; and ferric-reducing ability of plasma, FRAP), as well as the oxidative stress index (OSI) in seminal plasma (SP) with the resilience of horse sperm to freeze-thawing. Twenty-one ejaculates (one per individual) were collected and split into two aliquots: the first was used to harvest the SP and assess the activity levels of antioxidants and the OSI, and the second one was cryopreserved. The following post-thaw sperm quality parameters were evaluated: sperm motility, plasma membrane and acrosome integrity, mitochondrial membrane potential, intracellular levels of reactive oxygen species (ROS), and plasma membrane lipid disorder. Based on post-thaw total motility (TM) and plasma membrane integrity (SYBR14+/PI−), ejaculates were hierarchically (p < 0.001) clustered into two groups of good (GFE) and poor (PFE) freezability. The SP activity levels of PON1, SOD, and TEAC were higher (p < 0.05) in GFE than in PFE, showing a positive relationship (p < 0.05) with some sperm motility parameters and with plasma membrane (PON1 and TEAC) and acrosome (SOD and TEAC) integrity. In contrast, OSI was higher (p < 0.05) in the SP of PFE than in that of GFE, and was negatively correlated (p < 0.05) to some sperm motility parameters and to plasma membrane and acrosome integrity, and positively (p < 0.05) to the percentage of viable sperm with high plasma membrane lipid disorder. In conclusion, enzymatic (PON1 and SOD) and non-enzymatic (TEAC) antioxidants of SP are related to horse sperm cryotolerance. In addition, our results suggest that PON1 could be one of the main antioxidant enzymes involved in the control of ROS in this species. Further investigation is needed to confirm the potential use of these SP-antioxidants and OSI to predict sperm cryotolerance in horses.

Phospholipase C zeta characterization and egg activation ability of donkey sperm

Assisted reproduction in horses has rapidly increased in the last few years. This has opened the opportunity to explore its application in other equids, such as donkeys, considered vulnerable or endangered. Up to date, no in vitro blastocyst production has been reported in donkeys. Our work aimed to describe the localization of donkey phospholipase C zeta (PLCζ), considered to be the physiological molecule responsible for generating calcium oscillations that induce egg activation, and to compare the ability of the donkey sperm to induce the pronuclear formation and recruit maternal SMARCA4 when injected into pig eggs through ICSI. Frozen ejaculated sperm cells from two jacks and three stallions were used. IF using PLCζ and SMARCA4 antibodies were performed in sperm and zygotes respectively. Zygotes were fixed 18 h after injection. Four different main patterns of PLCζ expression were observed after analyzing a total of 590 sperm cells: F, flagellum only; A, acrosomal; PA, post-acrosomal, and A+PA: acrosomal and post-acrosomal. Surprisingly, around 60% of donkey sperm expressed F and A PLCζ localization, whereas in horses, PA and A+PA were the most common patterns (∼80%). All sperm cells showed flagellum localization of PLCζ. Interestingly, pig oocytes were significantly less activated after injection with donkey sperm than horse sperm ( Table 1 ),although SMARCA4 pronuclear localization levels in the zygotes were similar among groups. Our results describe for the first time the expression pattern of PLCζ in the donkey sperm. Moreover, we observed that horse sperm has a significantly increased ability to induce pig oocyte activation compared to the donkey. Since PLCζ is a crucial molecule for oocyte activation, we hypothesize that the different patterns of localization described for donkey sperm could be associated with low activation rates observed when injected into the egg. Therefore, strategies to improve the in vitro development of donkey ICSI embryos, such as assisted activation, might be required. More research is needed to confirm these preliminary results.

Use of specific mitochondrial complex inhibitors to investigate mitochondrial involvement on horse sperm motility and ROS production

Equine spermatozoa highly rely on oxidative phosphorylation for their energy management.The present work aimed to characterize the role of mitochondria on horse sperm motility and ROS production by incubating spermatozoa with specific inhibitors of the different mitochondrial complexes. Equine spermatozoa were incubated 1 h and 3 h at 37 °C with: complex I inhibitor rotenone (5 μM, ROT), complex II inhibitor dimethyl-malonate (10 mM, DMM), complex III inhibitor antimycin A (1.8 μM, ANTI), the uncoupling agent carbonyl cyanide m-chlorophenyl hydrazine (5 μM, CCCP), ATP synthase inhibitor oligomycin (5 μM, OLIGO), and 2 μL vehicle DMSO (control, CTL). Samples were analyzed for sperm motility and for mitochondrial membrane potential (MMP), mitochondrial integrity, mitochondrial O2•– production, and cytoplasmic H2O2. A multivariate analysis was performed on the data.CCCP caused a pronounced MMP reduction at both time points while ROT and ANTI showed the same effect at 3 h. All treatments at 3 h incubation significantly reduced the percentage of sperm with early changes in membrane permeability with active mitochondria. The H2O2 production of live cells was low at 1 h incubation in all treatments; after 3 h a slight decrease in the percentage of low-H2O2 producing cells was recorded. All treatments, except DMM, induced a significant decline in sperm motility and kinematics and modified the pattern of sperm subpopulations. The effect of DMM was evident only after 3 h, increasing the percentage of slow sperm subpopulation.In conclusion, the disruption of mitochondrial integrity induces an increase of mitochondrial ROS production that could be detrimental for cell function and survivior.

Impact of glyphosate and its formulation Roundup® on stallion spermatozoa

The growing and widespread use of glyphosate-based herbicides (GBHs) has raised an intense public debate about the impact of environmental contamination on animal and human health, including male fertility. The aim of this study was to deepen the impact of glyphosate (Gly) and GBHs on mammalian sperm investigating the effect of in vitro exposure of stallion spermatozoa to Gly and to its commercial formulation Roundup® (R).Spermatozoa were incubated at 37 °C with different Gly or R concentrations (from 0.5 to 720 μg/mL Gly or R at the same Gly-equivalent concentrations). After 1 h of incubation motility, viability, acrosome integrity, mitochondrial activity and ROS production were assessed.Gly, at all the concentrations tested, did not induce any detrimental impact on the sperm quality parameters evaluated. Conversely, R starting from 360 μg/mL (Gly-equivalent dose) significantly (P < 0.05) decreased total and progressive motility, viability, acrosome integrity, mitochondrial activity and the percentage of live spermatozoa with intact mitochondria not producing ROS.Our results indicate that the commercial formulation R is more toxic than its active molecule Gly and that the negative impact on stallion sperm motility might be likely due to a detrimental effect mainly at membrane and mitochondrial level and, at least in part, to redox unbalance. Moreover, based on the data obtained, it can be hypothesized a species-specificity in sperm sensitivity to Gly and GBHs as horse spermatozoa were negatively influenced at higher concentrations of R compared to those reported in literature to be toxic for human and swine male germ cells.

A New Approach of Sperm Motility Subpopulation Structure in Donkey and Horse

This study aimed to characterize the sperm kinematic values with high frames per second, to define the subpopulation structure of a horse and a donkey and compare them. A total of 57 fresh semen ejaculates (26 Spanish and 16 Arabian horse breeds and 10 donkeys) were collected and subsequently analyzed for kinematic parameters using the Computer-aided sperm motility analysis ISAS®v1.2 system and using a Spermtrack® 10-μm depth counting chamber. Sequences were recorded at 250 frames per second, and eight kinematic parameters were automatically evaluated. All kinematic parameters showed significant differences between a donkey and a horse and between horse breeds. All ejaculates evaluated showed excellent semen motility characteristics, with significantly higher values for all kinematic parameters for donkeys compared with horses except for beat-cross frequency. Donkey sperm was faster and linear than the horse. Regarding horse breeds differences, the Spanish horse had higher average path velocity, curvilinear velocity, and beat-cross frequency compared with the Arabian horse. Spanish horse sperm was rapid, but Arab horse was more linear. The principal component analysis showed three sperm subpopulations in the ejaculate of donkeys and horses with a significantly different motility characteristic between them. The dominant subpopulation for both donkey and horse was for rapid, straight, and linear with a high beat sperm (38.2 and 41.7%, respectively), whereas the lowest subpopulation was for the slowest and non-linear sperms. This, plus slight differences in the distribution of these subpopulations between Arabian and Spanish horses, were found. In conclusion, higher frames permitted to have a new interpretation of motile subpopulations with species and breed differences. More so, future works on donkey and horse breed spermatozoa should take into account differences between breeds that may interfere and alter the real analysis performed.

Acrosome staining with Coomassie brilliant blue G or R on the horse spermatozoa

Acrosome staining with Coomassie brilliant blue G or R on the horse spermatozoa

Horse ooplasm supports in vitro preimplantation development of zebra ICSI and SCNT embryos without compromising YAP1 and SOX2 expression pattern.

Several equids have gone extinct and many extant equids are currently considered vulnerable to critically endangered. This work aimed to evaluate whether domestic horse oocytes support preimplantation development of zebra embryos obtained by intracytoplasmic sperm injection (ICSI, zebroid) and cloning, and to study the Hippo signaling pathway during the lineage specification of trophectoderm cells and inner cell mass cells. We first showed that zebra and horse sperm cells induce porcine oocyte activation and recruit maternal SMARCA4 during pronuclear formation. SMARCA4 recruitment showed to be independent of the genetic background of the injected sperm. No differences were found in blastocyst rate of ICSI hybrid (zebra spermatozoon into horse egg) embryos relative to the homospecific horse control group. Interestingly, zebra cloned blastocyst rate was significantly higher at day 8. Moreover, most ICSI and cloned horse and zebra blastocysts showed a similar expression pattern of SOX2 and nuclear YAP1 with the majority of the nuclei positive for YAP1, and most SOX2+ nuclei negative for YAP1. Here we demonstrated that horse oocytes support zebra preimplantation development of both, ICSI and cloned embryos, without compromising development to blastocyst, blastocyst cell number neither the expression of SOX2 and YAP1. Our results support the use of domestic horse oocytes as a model to study in vitro zebra embryos on behalf of preservation of valuable genetic.

Red-Light Irradiation of Horse Spermatozoa Increases Mitochondrial Activity and Motility through Changes in the Motile Sperm Subpopulation Structure.

Previous studies in other mammalian species have shown that stimulation of semen with red-light increases sperm motility, mitochondrial activity, and fertilizing capacity. This study sought to determine whether red-light stimulation using a light emitting diode (LED) at 620–630 nm affects sperm motility and structure of motile subpopulations, sperm viability, mitochondrial activity, intracellular ATP levels, rate of O2 consumption and DNA integrity of horse spermatozoa. For this purpose, nine ejaculates were collected from nine different adult stallions. Upon collection, semen was diluted in Kenney extender, analyzed, its concentration was adjusted, and finally it was stimulated with red-light. In all cases, semen was packaged in 0.5-mL transparent straws, which were randomly divided into controls and 19 light-stimulation treatments; 6 consisted of a single exposure to red-light, and the other 13 involved irradiation with intervals of irradiation and darkness (light-dark-light). After irradiation, sperm motility was assessed using a Computerized Semen Analysis System (CASA). Flow cytometry was used to evaluate sperm viability, mitochondrial membrane potential and DNA fragmentation. Intracellular levels of ATP and O2 consumption rate were also determined. Specific red-light patterns were found to modify kinetics parameters (patterns: 4, 2-2-2, 3-3-3, 4-4-4, 5-1-5, and 5-5-5 min), the structure of motile sperm subpopulations (patterns: 2, 2-2-2, 3-3-3, and 4-1-4 min), mitochondrial membrane potential (patterns: 4, 3-3-3, 4-4-4, 5-1-5, 5-5-5, 15-5-15, and 15-15-15 min), intracellular ATP levels and the rate of O2 consumption (pattern: 4 min), without affecting sperm viability or DNA integrity. Since the increase in some kinematic parameters was concomitant with that of mitochondrial activity, intracellular ATP levels and O2 consumption rate, we suggest that the positive effect of light-irradiation on sperm motility is related to its impact upon mitochondrial activity. In conclusion, this study shows that red LED light stimulates motility and mitochondrial activity of horse sperm. Additional research is needed to address the impact of red-light irradiation on fertilizing ability and the mechanisms through which light exerts its effects.

Functional Assessment of Diluent Choice for Semen Cryopreservation from Stallions with High and Low Freezability

Background: fertility rates using horse frozen-thawed semen remain lower than in other livestock species. This fact further suggests that horse semen hold intrinsic sensitivity to cryoinjury that must be investigated. Moreover, there is a substantial influence of genetic factors and diluent choice upon horse cryopreservation outcome. Collectively, these genetic and technical properties of horse semen could be explored to identify factors or conditions that may increase semen viability after freeze-thawing. The aim of this work was to evaluate the effect of diluents Botu-Crio®,Lactose-EDTA®, and INRA-82® on cryopreserved semen from stallions with high (HFA) and low freezability (LFA).Materials, Methods &amp; Results: frozen-thawed semen was evaluated for motility, membrane integrity, and sperm DNA fragmentation using the thermoresistance test (TRT). Comparisons for each parameter were done in a pair-wise fashion between HFA and LFA semen at one-hour intervals during the TRT (0 h - 4 h). Sperm motility in HFA, regardless of the diluent, was larger (P &lt; 0.05) than LFA, both on 0h and 1h. In the 2h evaluation, sperm motility using Botu-Crio® and Lactose-EDTA® was greater (P &lt; 0.05) for HFA. Analysis of sperm membrane integrity was similar between HFA and LFA semen (P &gt; 0.05) at 0 h and 3 h. Sperm DNA fragmentation was lower (P &lt; 0.05) in HFA semen at 0 h and 1 h. Discussion: frozen-thawed semen from stallions of high freezing ability showed greater motility at all analysis, irrespectively of diluent choice, suggesting a strong influence of genetic factors on cryopreservation outcome. Membrane integrity was similar immediately after thawing but did differ later on other TRT time-points, irrespectively of diluent choice. As observed for motility, it was expected that sperm cells of stallions of HFA would show higher membrane integrity than their LFA counterparts. Sperm DNA fragmentation was quite low for both groups, as described in horses. Surprisingly, sperm DNA fragmentation incidence was constant throughout the analysis for both HFA and LFA. It was initially envisioned that increased DNA fragmentation would be found in semen from LFA stallions, since it is caused by multiple origins such as genetic factors. In conclusion, the semen diluent affects horse sperm motility after thawing, particularly from stallions with lower semen freezability.

181 Equine androgenic embryos: ability of the equine sperm to develop in a heterospecific ooplasm

Androgenic haploid embryos were originally produced for the study of certain aspects of early embryo development. The generation of androgenic haploid embryos allows us to better understand the complementary parental contribution to embryonic development, and to examine the effects of haploid development on gene expression. Because mare oocytes for research are scarce, the generation of heterospecific androgenic embryos could be useful to study aspects of the biology of early embryo development, or to identify genes and their variations or mutations that are responsible for reproduction-related problems in mares and stallions, which is of interest for the breeding industry. Therefore, the aim of this work was to study the capability of equine sperm to induce embryonic development after injection into an enucleated oocyte from a different species. Porcine cumulus-oocyte complexes (COC) were obtained from abattoir ovaries and placed in 100-µL drops in vitro maturation (IVM) medium for 42h. Cumulus cells were removed with hyaluronidase and vortexing. Then, mature oocytes were subjected to intracytoplasmic sperm injection (ICSI) with stallion frozen-thawed semen (according to Rodriguez et al. 2015). Immediately after the last injection, the zona pellucida of injected oocytes was removed with protease treatment, the oocytes were treated with cytochalasin B, and the metaphase II enucleated with a 20-µm micropipette. Finally, embryos were placed in culture medium (SOF) in plates with the well-of-the-well (WOW) system. As control treatment, non-enucleated pig oocytes were injected with stallion (CE) and boar (CC) semen. At Day 4, embryos were evaluated for cleavage and number of blastomeres, and stained with Hoechst 33342 to verify the presence of DNA in each blastomere under the UV light. Embryos were stored for future PCR studies to validate the presence of equine DNA. Data were analysed by chi-squared test to compare the cleavage of both controls with the androgenic embryos. From a total of 53 androgenic haploid embryos, the cleavage rate was 62% (33/53). Embryos were cleaved in 2 to 4 cells in 72.7%, 5 to 8 cells in 18.2%, and 9+ cells in 9.1% at Day 4. Presence of DNA in all blastomeres was observed in 60.6% (20/33) of the androgenic haploid embryos, while 21.2% (7/33) of the embryos had 10 to 50% of blastomeres with DNA, and 18.6% (6/33) of the embryos did not have DNA in their blastomeres. The ICSI control embryos cleaved in 45.3% (34/75) and 64.9% (98/151) for groups CC and CE, respectively. Cleavage rates in control CE were significantly higher than those in control CC (P&amp;lt;0.004). No statistical difference was observed in the control groups versus androgenic embryos. This preliminary results showed that a heterospecific ooplasm can be successfully used to allow an equine sperm DNA to decondense and to develop, even in absence of the female counterpart. Using this method, copies of a single sperm DNA can be produced to potentially evaluate individual aspects of early embryo development concerning the male contribution. This is the first report of successful androgenic embryos using a heterospecific oocyte to create copies of a horse sperm DNA.

Effect of feeding pomegranate seed oil as a source of conjugated linolenic acid on Arabian stallion semen quality in cooled and postthawed condition.

The objective was to assess the influence of pomegranate seed oil supplementation on the quality of fresh, cooled and frozen-thawed Arabian breed stallion semen. Eight stallions (n=4 per group) received their normal diet (control group) or normal diet top dressed with 200ml of pomegranate seed oil (PSO group). Semen was collected every fifteen days for 90days. Stallions were reversed across the treatments after a sixty-day interval. In cooled and stored condition (2, 12 and 24hr), spermatozoa motion characteristics, membrane integrity, viability, morphology and lipid peroxidation were analysed. In frozen-thawed semen, sperm dynamic characteristics were analysed by CASA, acrosome status and mitochondrial activity (evaluated by Flow cytometry) determined. The effects of treatment, time, semen type and their interactions were submitted to PROCMIX (SAS® ), and means compared by the Tukey test. Also, collected semen samples were artificially inseminated to evaluate fertility and pregnancy rate after day 60 of the experiment. The results from fresh condition showed that semen volume, sperm concentration, abnormality and live sperm were not affected by dietary treatment (p>0.05). In cooled condition, the higher value for sperm plasma membrane integrity and viability was observed in PSO group compared to control after 24hr cooled and stored in 5°C. In postthawed condition, the higher value for CASA total motility and acrosome status was observed in PSO group compared to control group (p<0.05). One hundred and twenty-six mares were artificially inseminated for fertility trial using control and PSO groups' fresh semen. The average pregnancy rates were not significantly different between control and treated group (62.88% and 65.90%, respectively) (p>0.05). We concluded that under the conditions of this study, dietary supplementation of 200ml pomegranate seed oil seems to relatively improved Arabian horse sperm quality during storage in cooled and frozen condition via increasing plasma membrane integrity, viability and acrosome status, but did not improve the pregnancy rates.

Effects of staining method and clinician experience on the evaluation of stallion sperm morphology

Evaluation of sperm morphology is part of the assessment of fertility in human and animal reproduction. Analyses can be performed using different techniques, including the use of staining methods In our prospective study, the morphology of equine sperm was evaluated using 3 staining methods Diff-Quik, eosin-nigrosin, and SpermBlue, the latter being a relatively new stain commonly used for human sperm. Our hypotheses were that (1) SpermBlue allows easier assessment of horse sperm morphology and facilitates better identification of sperm abnormalities, and (2) sperm morphology classification differs depending on the evaluator’s experience. Semen was obtained from various horse breeds; 40 samples from stallions between 2 and 15 years of age were collected during the 2016 breeding season and stored in a 2% buffered formaldehyde solution until processing. For each sample, 3 semen smears were made and stained with Diff-Quik, eosin-nigrosin, and SpermBlue. All morphological parameters were then evaluated blindly using a light microscope by a novice evaluator and a more experienced evaluator. For each slide, 200 spermatozoa were examined randomly and classified according to their characteristics. For the identification of morphologically normal spermatozoa, no significant difference between evaluators was found with any of the staining methods used. In contrast, significant differences between evaluators were observed in the classification of some anomalies affecting mainly the midpiece and the tail. Poor dye fixation was observed with SpermBlue.