Effect of extender and amino acid supplementation on sperm quality of cooled-preserved Andalusian donkey (Equus asinus) spermatozoa

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.

Taurine induces hormesis in multiple biological models: May have transformative implications for overall societal health

This paper represents the first integrative assessment and documentation of taurine-induced hormetic effects in the biological and biomedical areas, their dose response features, mechanistic frameworks, and possible public health, therapeutic and commercial applications. Taurine-induced hormetic effects are documented in a wide range of experimental models, cell types and for numerous biological endpoints, with most of these experimental findings being reported within the past five years. It is suggested that the concept of hormesis may have a transformative effect on taurine research and its public health and therapeutic applications.

Effects of intratesticular injection of hypertonic mannitol and saline on the quality of donkey sperm, indicators of oxidative stress and testicular tissue pathology

OBJECTIVES

The aim of the present study was to examine donkey sperm quality after intratesticular injection of hypertonic mannitol (HM) and saline (HS).

METHODS

Randomly assigned to five treatment groups were 15 adult male donkeys: (1) Control group (no treatment), (2) Surgery group (surgical castration for testosterone control), (3) NS group (normal saline intratesticular injection), (4) HS group (hypertonic saline), and (5) HM group. We injected 20 mL per testicle. We took 5 mL blood from all donkeys before injection. Castration was performed under general anesthesia 60 days later. Samples included blood and testicular tissue. Total motility (TM), progressive motility (PM), movementy features, DNA damage, morphology, viability, and plasma membrane functionality were evaluated. Hormone analyses, histomorphometric studies and oxidative stress indices including total antioxidant capacity (TAC), glutathione peroxidase (GPx), glutathione (GSH), superoxide dismutase (SOD), malondialdehyde (MDA), and NADP+/NADPH were evaluated. Apoptosis, pyroptosis-related Bax, Caspase-1, GSDMD, and Bcl-2 expression were also assessed.

RESULTS

In HS and HM groups, testosterone, epididymal sperm count, motility, viability, and plasma membrane functionality dropped while sperm DNA damage increased. HS and HM groups had significantly lower histomorphometric parameters, TAC, GPx, SOD, GSH, and Bcl-2 gene expression. MDA, NADP+/NADPH, Bax, Caspase-1, and GSDMD gene expression were substantially higher in the HS and HM groups than in the control group.

CONCLUSIONS

Toxic effects of hypertonic saline and mannitol on reproductive parameters were seen following, hence, they might be considered as a good chemical sterilizing treatment in donkeys.

Monitoring of taurine dietary supplementation effect on parameters of Duroc boar ejaculate in summer season

The aim of this experiment was to find out whether the taurine supplementation in daily ration had an effect on quantity or quality of Duroc boar ejaculate. The experiment duration was from June to August, when it could assumed the possible occurrence of heat stress. For the study was chosen 12 Duroc boars of approximately the same age and condition. The control group of 6 Duroc boars was fed only by basic diet and the experimental group of 6 Duroc boars was fed by the same basic diet with supplementation of 15 g taurine/boar/day. Ejaculate was collected once a week by hand glowed technique. From ejaculate parameters were monitored volume of ejaculate, sperm concentration, total amount of sperm, morphologically abnormal sperm, taurine concentration and GSH/GSSH concentration. From microscopic analysis, results were statistically significant in motility in June and July (P<0.05). In biochemical results, a significant difference (P<0.05) has been found between the experimental groups in the concentrations of taurine as well as GSH/GSSG in ejaculate which indicates the effect of heat stress on boars during the experimental period.

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.

Combined addition of L-carnitine and L-proline improves cryopreservation of dairy goat semen

Cryopreservation of semen renders artificial insemination easier and cheaper compared to use of fresh semen. However, the cellular oxidative stress, toxicity of cryoprotectants, and osmotic imbalance may lead to a decline in semen quality and fertilization ability during the process of cryopreservation. L-carnitine and L-proline have been demonstrated to possess effective antioxidant properties in cryopreservation, with the latter also exhibiting excellent permeability and thus being utilized as a permeable cryoprotectant in the field. The aim of this study was to investigate the effects of LC and LP on cryopreservation of semen of dairy goats. After thawing, sperm motility, membrane integrity, and acrosome integrity rate of cryopreserved semen treated with LC (50 mM) were significantly higher compared to the untreated control samples. Based on this premise, we conducted experiments to assess the cryoprotective efficacy of different concentrations of LP. The findings demonstrated that the inclusion of 50 mM LP resulted in improved sperm motility compared to other concentrations. Furthermore, the levels of damaging reactive oxygen species and the malonyldialdehyde marker for oxidative stress were significantly lower in goat semen treated with these concentrations of LC and LP compared to semen exposed to other treatments. Semen treated with LC and LP also exhibited good fertilization ability during both in vitro fertilization and artificial insemination. Thus, LC (50 mM) and LP (50 mM) improve cryoprotection of dairy goat sperm which suggests that addition of these compounds will be highly beneficial to the development of dairy goat breeding.

Role of antioxidants in fertility preservation of sperm - A narrative review

Male fertility is affected by multiple endogenous stressors, including reactive oxygen species (ROS), which greatly deteriorate the fertility. However, physiological levels of ROS are required by sperm for the proper accomplishment of different cellular functions including proliferation, maturation, capacitation, acrosomal reaction, and fertilization. Excessive ROS production creates an imbalance between ROS production and neutralization resulting in oxidative stress (OS). OS causes male infertility by impairing sperm functions including reduced motility, deoxyribonucleic acid damage, morphological defects, and enhanced apoptosis. Several in-vivo and in-vitro studies have reported improvement in quality-related parameters of sperm following the use of different natural and synthetic antioxidants. In this review, we focus on the causes of OS, ROS production sources, mechanisms responsible for sperm damage, and the role of antioxidants in preserving sperm fertility.

TMT-based comparative proteomic analysis of Dezhou donkey spermatozoa related to freezability

The freezability difference between donkey ejaculates is a limiting factor of sperm cryopreservation. Our recent study shows that the freezability of donkey semen is related to the seminal plasma proteome. In this study, we aimed to identify the different abundance sperm proteins in good freezability ejaculates (GFEs) and poor freezability ejaculates (PFEs) using a Tandem Mass Tag (TMT) peptide labeling coupled with LC-MS/MS approach. A total of 2682 proteins were identified, among which 58 were significantly up-regulated in GFEs and 16 were down-regulated compared with PFEs. Bioinformatic analysis results revealed that the majority of different abundance proteins (DAPs) participated in copper and calcium binding, regulation of RNA biosynthetic process, positive regulation of innate immune response, and negative regulation of programmed cell death. KEGG pathway enrichment analysis showed the up-regulated proteins in GF group were mainly involved in N-Glycan biosynthesis and protein processing in endoplasmic reticulum. Our study was the first to analyze the proteome of sperm from donkey ejaculates with different freezabilities. The identified candidate proteins might be used to explore the molecular mechanism related to donkey sperm cryotolerance and might improve the screening of jacks with good sperm freezability. SIGNIFICANCE: Cryopreserved semen has been widely used in assisted reproductive technology. However, semen cryopreservation is a damaging process, which can cause oxidative stress, reduce sperm motility and motility. There are differences in sperm freezability reported to exist between or within breeds, and even between fractions coming from the same ejaculate. The freezability difference between donkey ejaculates is a limiting factor of sperm cryopreservation. The mechanisms that affect the freezing difference in sperm quality remain to be investigated, and freezability differences was found to be related to protein composition of spermatozoa. Some protein markers that can indicate good freezability or poor freezability semen have been identified in mammals. Until now, there is no information about the relationship between donkey spermatozoa proteome and freezability. Additional novel biomarkers of semen freezability in donkey spermatozoa are also needed. The identified candidate proteins might be used to explore the molecular mechanism related to donkey sperm cryotolerance and might improve the screening of jacks with good sperm freezability.

Beneficial Effect of Proline Supplementation on Goat Spermatozoa Quality during Cryopreservation

Sperm cryopreservation contributes to the extensive utilization of artificial insemination (AI) in the daily livestock industry. However, due to the presence of few sperm with good biological function in post-thaw goat sperm, its use has been limited for AI purposes. Hence, its improvement has been the focus of many research studies. This study aimed to investigate the effects of proline supplementation of the freezing medium on goat sperm. The goat semen was cryopreserved with freezing medium supplementation of different concentrations of proline (0, 0.5, 1, 2 and 4 mM). The post-thaw sperm motility patterns, membrane integrity, acrosome integrity, lipid peroxidation (LPO) levels, malondialdehyde (MDA) levels, total antioxidant capacity (T-AOC), proline dehydrogenase (PRODH) activity, superoxide dis-mutase (SOD) activity, glutathione (GSH) levels and GSH/GSSG were evaluated. Likewise, the expression and immunofluorescent localization of PRODH in post-thaw goat sperm was also detected. It was observed that addition of 2 mM proline to the freezing medium significantly enhanced post-thaw goat sperm total motility, progressive motility, straight-linear velocity (VSL), curvilinear velocity (VCL), average path velocity (VAP), straightness (STR), linearity (LIN), membrane integrity and acrosome integrity. Interestingly, PRODH was expressed in post-thaw goat sperm, especially in the post-acrosome and sperm tail. Addition of 2 mM proline also significantly increased the post-thaw sperm PRODH activity compared to the control. Moreover, post-thaw goat sperm LPO levels and MDA levels were reduced by supplementation of 2 mM proline. Furthermore, compared to the control, the values of post-thaw goat sperm T-AOC, SOD activity, GSH level and GSH/GSSG were also significantly increased in 2 mM proline treatment. Reduction of post-thaw goat sperm apoptosis in 2 mM proline treatment was also observed as the levels of Caspase3 and Caspase9 were decreased by the supplementation with 2 mM proline. These observations suggest that the addition of 2 mM proline to the freezing medium increased post-thaw goat sperm quality by reducing oxidative stress during cryopreservation. These findings also provide novel insights into the use of proline as an efficient additive to enhance post-thaw goat sperm quality during cryopreservation.

Ability of donkey sperm to tolerate cooling: Effect of extender base and removal of seminal plasma on sperm parameters and fertility rates in mares

Artificial insemination using cooled-transported semen has marked importance in equine breeding programs around the world, and the high value of mules has generated avid interest in donkey semen biotechnology. However, donkey semen cools poorly in commercially available equine extenders. Therefore, this study aimed to develop approaches to improve the ability of donkey semen to tolerate cooling. Ejaculates of seven donkeys (n = 21) were cooled at 5°C for 48 h in three different extenders (milk-based, SM; sodium caseinate-based, SC; or egg yolk-based, EY) in the presence or absence of seminal plasma (centrifugation, C). Sperm motility, plasma membrane integrity (PMI), plasma membrane stability (PMS), mitochondrial membrane potential (HMMP), intracellular hydrogen peroxide (H₂O₂), and intracellular superoxide (O2−) were assessed before, 24 h, and 48 h post-cooling. In addition, 15 mares (163 estrous cycles) were randomly inseminated with semen from two jacks (Jack 1, n = 90; Jack 2, n = 73) previously cooled for 24 h under one of the treatments (SM, SC, EY, SM-C, SC-C, or EY-C). Groups EY, SC-C, and EY-C (P < 0.05) demonstrated superior sperm analytical parameters to SM at 24 and 48 h. Centrifugation positively affected sperm analytical parameters in cooled donkey semen extended in SM and SC (P < 0.05). Mares bred with semen extended in SC (67%, 18/27), SC-C (89%, 24/27), EY (89%, 25/28), or EY-C (74%, 20/27) had significantly greater conception rates than mares bred with SM (33%, 9/27; P < 0.05). Mares bred with SM-C had intermediate conception rates (59%, 16/27). In conclusion, SC and EY improved the cooling ability and fertility of donkey semen in horse mares, and centrifugation positively affected donkey semen extended in SM.

Beneficial effect of L-Proline supplementation on the quality of human spermatozoa

L-Proline is a natural anti-oxidative and osmoprotectant agent, playing a versatile role in cell metabolism and physiology. The present study aimed to explore the antioxidant effects of L-Proline on human sperm function during incubation. Thirty healthy, normozoospermic men (27-40 years) were enrolled. Sperm samples were incubated in an unsupplemented sperm medium (control group), or supplemented with L-Proline (1, 2 and 4 mmol/L) to evaluate its effect during 0, 1, 4 and 24 h of incubation. Sperm were assessed in terms of motility, viability, morphology, chromatin and DNA integrity. Moreover, the levels of reactive oxygen species (ROS), malondialdehyde (MDA), and total antioxidant capacity (TAC) were determined in the sperm medium. The results indicated that 2 mmol/L of L-Proline significantly improved the maintenance of sperm motility, viability, normal morphology, chromatin and DNA integrity, and TAC levels compared to the control group during 24 h of incubation (p < 0.05). However, 1 and 4 mmol/L of L-Proline could not significantly preserve sperm parameters, chromatin quality, and antioxidant status during different incubation times compared to the control group (p > 0.05). Collectively, the inclusion of L-Proline (2 mmol/L) in the human sperm medium maintains sperm parameters and chromatin quality probably by modulating the oxidative status.

Exogenous gonadotropin-releasing hormone counteracts the adverse effect of scrotal insulation on testicular functions in bucks

This study determined the effects of scrotal insulation on testicular functions in bucks and evaluated the impact of exogenous gonadotropin-releasing hormone (GnRH) administration before scrotal insulation on sperm production and testicular vascular dynamics. Twelve bucks were randomly divided into three groups: scrotal-insulated animals without GnRH treatment (INS), scrotal-insulated animals treated previously with GnRH (GnRH + INS), and animals without insulation as controls (CON). Doppler ultrasonography was used to evaluate testicular vascular changes, and semen samples were collected to assess seminal parameters. Testicular samples were collected from slaughtered bucks at the end of the experiment for histological investigations and immunohistochemical analysis for caspase 3 (apoptotic marker), and a vascular endothelial growth factor (VEGF; hypoxic marker) evaluation. Sperm motility drastically decreased (33%) in the INS group on day 8 compared with those in the GnRH + INS and CON groups (58% and 85%, respectively). Testicular blood flow significantly decreased for 3 and 2 weeks in the INS and GnRH + INS groups, respectively. The pulsatility index (PI) reached pretreatment values at 5 and 4 weeks after insulation in the INS and GnRH + INS groups, respectively. The resistance index (RI) values increased in both insulated groups for the first 2 weeks and decreased to control values 4 weeks after insulation. However, the maximum velocity (VP) started to increase reaching pretreatment values by the 5th and 3rd weeks after insulation in the INS and GnRH + INS groups, respectively. Histological investigations showed a marked reduction in lipid inclusions in Sertoli cells in the GnRH + INS group compared with those in the INS group. The distributions of both caspase 3 and VEGF decreased in the GnRH + INS group compared with those in the INS group. This study showed that the administration of a single dose of GnRH delayed the negative effects of scrotal insulation on different seminal traits and revealed the pivotal role of GnRH in compensating testicular insulation in bucks.

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.

Effects of Taurine on Sperm Quality during Room Temperature Storage in Hu Sheep

Simple Summary

Hu sheep sperm is highly susceptible to ROS during storage at room temperature. It is very important to use an antioxidant to ameliorate oxidative damage. Tau is an important amino acid peptide antioxidant with a wide range of biological effects. It can effectively scavenge free radicals, regulate reproductive function, improve immunity, and enhance its antioxidant capacity. However, the effects of Tau in the preservation of Hu sheep semen at room temperature are unclear. Therefore, Tau was added to Hu sheep semen preserved at room temperature to explore its effect on semen. The results showed that adding an appropriate concentration of Tau had a positive effect on Hu sheep semen preserved at room temperature; in particular, 20 mM Tau performed best.

Abstract

The present study aimed to investigate whether the presence of Tau protected Hu sheep sperm from ROS stress during storage at room temperature. The semen was diluted with extender (Tris-based) at room temperature, supplemented with different concentrations of Tau (0, 10, 20, 40, 80, or 100 mM), and stored at 15 °C. Sperm quality parameters (sperm progressive motility, kinetic parameters, plasma membrane integrity rate, acrosome integrity rate, and MMP) and antioxidant parameters (ROS, MDA, SOD, CAT, and T-AOC) were evaluated during the preservation of semen. The addition of Tau, especially at a concentration of 20 mM, exerted positive effects on sperm quality parameters and antioxidant parameters compared to the sperm without Tau treatment (control group). The addition of Tau, especially at a concentration of 100 mM, exerted negative effects on sperm quality parameters and antioxidant parameters compared to the control group. Interestingly, the results indicated that the sperm acrosome integrity rate did not change during storage time. In conclusion, the addition of Tau to sperm preserved at room temperature can enhance the antioxidant ability of sperm, reduce the LPO on the 5th day, and improve the quality of semen preserved at room temperature. These results implied that Tau had potential to enhance Hu sheep sperm reproductive performance.

Role of Antioxidants in Cooled Liquid Storage of Mammal Spermatozoa

Cooled preservation of semen is usually associated with artificial insemination and genetic improvement programs in livestock species. Several studies have reported an increase in reactive oxidative species and a decrease in antioxidant substances and sperm quality parameters during long-term semen storage at refrigerated temperatures. The supplementation of antioxidants in extenders before refrigeration could reduce this detrimental effect. Various antioxidants have been tested, both enzymatic, such as superoxide dismutase and catalase, and non-enzymatic, such as reduced glutathione, vitamins E and C and melatonin. However, the problem of oxidative stress in semen storage has not been fully resolved. The effects of antioxidants for semen-cooled storage have not been reviewed in depth. Therefore, the objective of the present study was to review the efficiency of the supplementation of antioxidants in the extender during cooled storage of semen in livestock species.

L-Proline: An Effective Agent for Frozen and Post-thawed Donkey Semen Storage

The aim of this study was to evaluate the effects of L-proline on the extender quality of frozen and post-thawed jackass semen. Jackass (n = 6) semen samples were collected and cryopreserved in gradient concentrations (0-80 mM) of L-proline in extenders; post-thawed semen samples were cultured in L-proline medium for 10 hours at 37°C. For cryopreservation experiment I, the motile parameters, mitochondrial membrane potential (MMP), and plasma membrane, acrosome, and chromatin structure integrities of post-thawed semen were assessed. For culture experiment II, additional ROS contents were analyzed after incubation. For the fertility trial, jennies (n = 135) were divided into group I (30 mM L-proline in cryopreservation extender), group II (40 mM L-proline in culture medium), and the control. Pregnancy was diagnosed using an ultrasound scanner 30 days after ovulation. The results of experiment I showed that, motile parameters and acrosome and chromatin structure integrities of groups I and 40 mM were significantly higher than the control (P < .05). MMP of group I was significantly higher than the control and 40 mM groups (P < .05). In experiment II, after 4 hours of incubation, motile parameters, MMP, and DNA integrity in group II were significantly higher than the control (P < .05). Additionally, 40 and 80 mM L-proline in culture medium significantly reduced ROS accumulation after 4 and 10 hours of incubation (P < .05). Pregnancy rates of the control and groups I and II were 28.85%, 40%, and 36.84%, respectively. In conclusion, the extenders containing 30 to 40 mM L-proline improved both qualities of frozen and post-thawed semen, and it will be a beneficial agent for donkey frozen spermatozoa or post-thawed semen storage.

Bayesian Linear Regression Modelling for Sperm Quality Parameters Using Age, Body Weight, Testicular Morphometry, and Combined Biometric Indices in Donkeys

Simple Summary

The prediction of sperm output and other reproductive traits based on testicular biometry is an important tool in the reproductive management of stallions. Nevertheless, corresponding research in donkeys remains scarce. Several donkey breeds in Europe face a compromising threat of extinction, which has been accelerated by the low renovation of populations and their inbreeding levels. Although research on female reproductive physiology has made crucial advances, much less is known about the physiology of the male. In the present work, two Bayesian models were built to predict for sperm output and quality parameters in donkeys. Models included combinations of age as a covariate and biometric and testicular measurements as independent factors. Results evidenced that the goodness-of-fit was similar for both models—hence, the combination of biometry and testicular factors presented improved predictive power. The application of these models may assist in the process of making decisions in respect to the reproductive/biological, clinical, and selection handling of the animals.

Abstract

The aim of the present study is to define and compare the predictive power of two different Bayesian models for donkey sperm quality after the evaluation of linear and combined testicular biometry indices and their relationship with age and body weight (BW). Testicular morphometry was ultrasonographically obtained from 23 donkeys (six juveniles and 17 adults), while 40 ejaculates from eight mature donkeys were analyzed for sperm output and quality assessment. Bayesian linear regression analyses were considered to build two statistical models using gel-free volume, concentration, total sperm number, motility, total motile sperm, and morphology as dependent variables. Predictive model 1 comprised the covariate of age and the independent factors testicular measurements (length, height and width), while model 2 included the covariate of age and the factors of BW, testicular volume, and gonadosomatic ratio. Although goodness-of-fit was similar, the combination of predictors in model 1 evidenced higher likelihood to predict gel-free volume (mL), concentration (×10⁶/mL), and motility (%). Alternatively, the combination of predictors in model 2 evidenced higher predictive power for total sperm number (×10⁹), morphologically normal spermatozoa (%), and total motile sperm count (×10⁹). The application of the present models may be useful to gather relevant information that could be used hereafter for assisted reproductive technologies.

First pregnancies in jennies with vitrified donkey semen using a new warming method

Sperm vitrification has been recently developed, but fertility trials have not been performed yet in equine species. In this study, a new warming technique for vitrified donkey semen was developed and the uterine inflammatory response and fertility were compared to conventional freezing. In Experiment 1, sperm was vitrified in straws and warmed in 3 ml of extender or in a water bath at: 37 °C/30 s; 43 °C/10 s; and 60 °C/5 s. Sperm motility, plasma and acrosome membranes and DNA integrity were compared between treatments. In Experiment 2, jennies were inseminated twice (500 × 10⁶ sperm) in the uterine body either with vitrified or frozen semen (2 cycles/jenny). Pregnancy rates and the uterine inflammatory response (polymorphonuclear neutrophil concentration; PMN) were evaluated after artificial insemination (AI). No differences between warming in extender/water bath were found and 43 °C/10 s was better than lower temperatures in terms of total (53.8 ± 13.2%) and progressive sperm motility (41.4 ± 11.4%). No differences in PMN concentration (×10³ PMN/ml) were found between vitrified (276.8 ± 171.6) or frozen (309.7 ± 250.7) semen after AI. However, PMN decreased faster (P < 0.05) using vitrified semen. Pregnancy rates were greater for vitrified (22%) than frozen semen (10%) but not statistically different. In conclusion, donkey sperm vitrified in straws could be directly warmed in a water bath at 43 °C/10 s, reducing the uterine inflammatory response obtained after AI and promoting positive pregnancy outcomes. These findings confirm the possibility to use vitrified semen as an alternative for AI in jennies.

Antimicrobial activity of silver-carbon nanoparticles on the bacterial flora of bull semen

The spermicidal effects of silver nanoparticles (AgNPs) hinder its application in the field of artificial insemination. In this study, silver-carbon NPs (Ag@C NPs) was synthesized and applied as an alternative antibiotic agent for bull semen extender. Ag@C NPs were characterized using X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), atomic absorption flame spectroscopy, transmission electron microscope (TEM), and high-resolution TEM (HR-TEM). Data analysis revealed the successful synthesis of Ag@C NPs with a particle size of 1-5 nm (average particle size of 2.5 nm) embedded into carbon. The antimicrobial activity of Ag@C NPs was tested against bacteriospermia of fresh semen collected from five fertile bulls (three ejaculates/bull). Escherichia coli (E. Coli), Staphylococcus aureus (S. aureus), and Pseudomonas aeruginosa (P. aeruginosa) were isolated from fresh semen samples and identified by culture, staining, and conventional biochemical tests. The minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) of Ag@C NPs against bacteriospermia was determined at 5 and 37 °C. Ag@C NPs showed efficient antimicrobial activity (MIC: 3.125-12.5 μg/mL) against the tested strains and strong bactericidal effect on S. aureus, and P. aeruginosa (MBC: 3.125 μg/mL), with no detrimental effect (P ˃ 0.05) on the percentage of sperm motility (70.71 ± 4.82; 74.65 ± 4.46), plasma membrane integrity (68.39 ± 4.31; 72.38 ± 4.91), acrosome integrity (88.40 ± 13.21; 86.77 ± 14.23), and normal sperm morphology (86.85 ± 7.43; 87.82 ± 8.15) at concentrations of 15 and 30 μg/mL, respectively, after a cold storage of 48 h. However, Ag@C NPs showed a detrimental effect on sperm parameters in a dose dependent manner at concentrations ≥60 μg/mL. Ag@C NPs showed no adverse effect on the sperm's ultrastructure with limited sperm internalization at MIC. In conclusion, Ag@C NPs could be used as an alternative antibiotic agent for bull semen extender without a significant cytotoxic effect on the sperm during cold storage. However, further investigations for their effects on embryo production and female genitalia are still required.

Fertilizing capacity of vitrified stallion sperm assessed utilizing heterologous IVF after different semen warming procedures

The aim of this study was to evaluate the fertilizing capacity of frozen or vitrified stallion sperm after assessing different warming procedures. In Experiment 1, different warming procedures were compared after sperm vitrification: immersion in extender at 43 °C (C), or in a water bath at 37 °C/30 s (W37), 43 °C/10 s (W43) or 60 °C/5 s (W60). With the W60 treatment, there were greater values (P < 0.05) for VCL (83.93 ± 3.6 μm/s) and ALH (3.00 ± 0.2 μm) than freezing and with the C group, and greater values (P < 0.001) for PM (35.33 ± 2.5 %) than with the W43 treatment. In Experiment 2, the fertilizing capacity of vitrified and frozen sperm was assessed utilizing heterologous IVF procedures, using cattle oocytes. Vitrification resulted in greater values (P < 0.05) than freezing for the number of bound sperm (1.36 ± 0.3 and 0.69 ± 0.2, respectively). There were no differences between frozen or vitrified sperm in pronuclear formation (26 hours post-insemination - hpi; 14.08 ± 4.2 % and 22.78 ± 4.8 %, respectively) or cleavage rate (32.77 ± 4.3 % and 39.66 ± 4.6 %, respectively). In conclusion, vitrified stallion sperm warmed in a water bath at 60 ºC had the capacity to penetrate cattle oocytes, leading to pronuclear formation and hybrid embryo cleavage after heterologous IVF.

Proline Protects Boar Sperm against Oxidative Stress through Proline Dehydrogenase-Mediated Metabolism and the Amine Structure of Pyrrolidine

Simple Summary

Reactive oxygen species that accumulate during liquid storage of boar semen lead to oxidative stress to sperm. In this study, we found that proline significantly improved boar sperm quality and protected sperm against oxidative damages during liquid storage at 17 °C. Using the model of artificially induced oxidative stress, we found that proline exerted an antioxidative role by modulating redox homeostasis in boar sperm. The secondary amine structure of proline and proline dehydrogenase-mediated metabolism are involved in the antioxidative role. We suggest that addition of proline to the extender would be beneficial to improve boar sperm quality.

Abstract

Proline was reported to improve sperm quality in rams, stallions, cynomolgus monkeys, donkeys, and canines during cryopreservation. However, the underlying mechanism remains unclear. The aim of this study was to investigate the effect of proline on boar semen during liquid storage at 17 °C and explore the underlying mechanism. Freshly ejaculated boar semen was supplemented with different concentrations of proline (0, 25, 50, 75, 100, 125 mM) and stored at 17 °C for nine days. Sperm motility patterns, membrane integrity, ATP (adenosine triphosphate), reactive oxygen species (ROS), and GSH (glutathione) levels, and the activities of catalase (CAT) and superoxide dismutase (SOD) were evaluated after storage for up to five days. It was observed that boar sperm quality gradually decreased with the extension of storage time, while the ROS levels increased. Addition of 75 mM proline not only significantly improved sperm membrane integrity, motility, and ATP levels but also maintained the redox homeostasis via increasing the GSH levels and activities of CAT and SOD. When hydrogen peroxide (H₂O₂) was used to induce oxidative stress, addition of proline significantly improved sperm quality and reduced ROS levels. Moreover, addition of proline also improved sperm quality during the rapid cooling process. Notably, addition of DL-PCA (DL-pipecolinic acid) rescued the reduction of progressive motility and total motility caused by H₂O₂, and THFA (tetrahydro-2-furoic acid) failed to provide protection. Furthermore, addition of proline at 75 mM increased the activity of proline dehydrogenase (PRODH) and attenuated the H₂O₂-induced reduction in progressive motility. These data demonstrate that proline protects sperm against oxidative stress through the secondary amine structure and proline dehydrogenase-mediated metabolism.

Nano-depletion of acrosome-damaged donkey sperm by using lectin peanut agglutinin (PNA)-magnetic nanoparticles

Lectin is considered as a suitable biomarker for nano-depletion of acrosome-damaged sperm. The aim of this study was to synthetize magnetic nanoparticles (MNPs) coated by peanut (Arachis hypogaea) agglutinin lectin (PNA) and investigate its beneficial effect in improving of sperm characteristics. MNPs were obtained by co-precipitation method, functionalized with chitosan and coated by PNA at a concentration of 0.04 mg/mL. Semen was frozen either with glycerol-based or sucrose-based extenders. Frozen-thawed straws from five donkeys (three ejaculates per donkey) were incubated with lectin-MNPs (2 mg/mL), and then exposed to an external magnet enabling the non-bound sperm to be collected as nanopurified sperm. Sperm were evaluated post-thawing (control) and after nanopurification for motility, plasma membrane integrity, acrosome integrity, morphology, DNA fragmentation and concentration. The statistical analyses were extended to investigate the correlation between the initial quality of the frozen-thawed semen samples and the effect of nanopurification after thawing. The obtained MNPs were biocompatible to the sperm and significantly improved the progressive motility (P < 0.05) for the glycerol nanopurified group (43.08 ± 3.52%) in comparison to control (33.70 ± 2.64%). Acrosome-damaged sperm were reduced (P < 0.05) in both nanopurified groups (19.92 ± 2.69 for G and 21.57 ± 2.77 for S) in comparison to control (36.07 ± 3.82 for G and 35.35 ± 3.88 for S). There were no significant changes in sperm morphology and membrane integrity after nanopurification. The average sperm recovery after nanopurification was 80.1%. Sperm quality index was significantly higher (P < 0.001) in nanopurified groups regardless of the initial quality of the frozen thawed semen samples. However, in the high sperm quality group, nanopurification significantly improved the progressive motility and membrane integrity besides the increasing of acrosome-intact sperm. Sperm nanopurification using lectin-magnetic nanoparticles can be considered as a suitable method to reduce the proportion of acrosome-damaged sperm and to increase the quality of frozen thawed donkey semen.

Cryopreservation of Andalusian donkey (Equus asinus) spermatozoa: Use of alternative energy sources in the freezing extender affects post-thaw sperm motility patterns but not DNA stability

The aim of this study was to compare the effect of three sugars and Equex paste in a freezing extender for donkey sperm cryopreservation. Ejaculates (n = 18) were collected from six Andalusian donkeys of proven fertility were pooled (two ejaculates per pool) and cryopreserved using a freezing extender containing three different sugars (glucose, fructose and sorbitol), with or without the addition of Equex paste. Sperm quality was assessed before and after freezing-thawing for motility, morphology, plasma membrane integrity, acrosome integrity and DNA integrity. The use of sorbitol in the freezing extender improved total and progressive sperm motility (P < 0.05) and amplitude of lateral head displacement (P < 0.01), but it reduced the values for other sperm motility variables compared with glucose (P < 0.001). The use of fructose resulted in a reduction in values for most CASA variables (P < 0.05), whereas addition of Equex paste did not have any beneficial effect on values for these variables (P > 0.05). Glucose was more effective in maintaining sperm morphology (P < 0.05), while there was no beneficial effect with the addition of Equex paste (P > 0.05). Supplementation of fructose and Equex paste in the freezing extender decreased plasma membrane integrity (P < 0.05) as compared with glucose, but there were no differences between treatments for acrosome and DNA integrity (P > 0.05), even after 24 h of incubation. The use of different sugar sources in the extender could affect the in vitro post-thaw quality of cryopreserved donkey spermatozoa, with sorbitol being an interesting alternative for improving the sperm quality. Results of the present study indicate the use of Equex paste could negatively affect post-thaw outcomes for sperm viability in this species.

Vitrification of stallion sperm using 0.25 ml straws: Effect of volume, concentration and carbohydrates (sucrose/trehalose/raffinose)

Sperm vitrification is a rapid freezing method in which carbohydrates are used as cryoprotectants. The aim of this study was to determine the optimal volume, concentration and type of carbohydrates for stallion sperm vitrification using 0.25 ml straws in comparison to conventional freezing. Ejaculates (n = 54) were collected from six stallions. For vitrification, straws were filled with different volumes (30, 70, 100 μl), sperm concentrations (50, 100, 200 × 10⁶ sperm/ml) and extenders containing sucrose (20, 100, 200 mM), trehalose (50, 100, 200 mM) and raffinose (50, 100, 200 mM) and plunged into LN₂. Conventional freezing was performed in 0.5 ml straws frozen in LN₂ vapors. Sperm motility, plasma and acrosome membrane integrities and DNA fragmentation were compared among treatments. The use of straws filled with 100 μl at 100 × 10⁶ sperm/ml with the extender containing 100 mM trehalose resulted in greater values for sperm quality than the other concentrations, volumes and carbohydrates. With vitrification, there were greater values (mean ± SEM; P < 0.05) than freezing for progressive motility (48.2 ± 2.3 compared with 37.3 ± 2.2%), plasma membrane integrity (82.8 ± 1.5 compared with 74.1 ± 1.9%), and intact acrosomes (50.2 ±  1.2 compared with 43.1 ± 1.4%); and less DNA fragmentation (6.4 ± 0.7 compared with 8.2 ± 0.3%). In conclusion, stallion sperm can be vitrified in 0.25 ml straws filled with 100 μl of sperm at 100 x 10⁶ sperm/ml using an extender with 100 mM of trehalose, obtaining better sperm quality after warming than conventional freezing.

Optimization of donkey sperm vitrification: Effect of sucrose, sperm concentration, volume and package (0.25 and 0.5 mL straws)

The aim of this study was to assess the effect of different factors affecting vitrification success of donkey sperm: extender, sperm concentration, volume and storage vessel type. In Experiment 1, sucrose supplementations at 0.25 and 0.1 M were compared using two base extenders (containing or not egg-yolk); in Experiment 2, three sperm concentrations were assessed: 100, 200 or 300 million sperm/mL; and in Experiment 3, three different sperm volumes (100, 160 and 200 μL) and two different storage vessels (0.25 and 0.5 mL straws) were assessed. Sperm motility variables (CASA), plasma membrane and acrosome (evaluated under fluorescence microscopy) and sperm DNA integrity (flow cytometry) were evaluated after warming with comparisons of protocols. There was a greater total (55.7 ± 16.4%) and progressive (44.0 ± 11.5%) motility using the extender with egg-yolk and 0.1 M sucrose. There were no effects of sperm concentrations on vitrification results (P > 0.05). The 0.25 mL covered straw showed higher values than the 0.5 mL straw for total (50.0 ± 17.3% vs 2.0 ± 6.7%) and progressive (40.5 ± 14.9% vs 0.9 ± 1.5%) motility, plasma membrane (43.9 ± 14.4% vs 14.0 ± 16.4%) and acrosome integrity (51.5 ± 13.6% vs 28.0 ± 14.7%), respectively. In conclusion, values for donkey sperm quality variables after vitrification were greater using an extender containing egg-yolk and 0.1 M sucrose, at 300 million sperm/mL in 0.25 mL straws with outer covers.

Freezability of Andalusian donkey (Equus asinus) spermatozoa: effect of extenders and permeating cryoprotectants

The aim of this study was to compare the effect of two semen extenders and four permeating cryoprotectants on post-thaw sperm quality of Andalusian donkeys. First, 32 ejaculates were pooled, split and frozen in either Gent B or INRA 96 with egg yolk and glycerol. Second, 12 pooled semen samples were simultaneously frozen in Gent B (glycerol) or Gent A containing ethylene glycol (EG; 1 or 1.5%) or dimethyl sulfoxide (DMSO; 1.5 or 2%). Finally, nine pooled samples were simultaneously cryopreserved in Gent A containing 1% EG (as control), dimethylformamide (DMFA; 1 or 2.5%) or a combination of 1% EG and 1.5% DMFA. Gent B yielded a higher (P<0.01) post-thaw sperm motility than modified INRA96. EG 1% increased the sperm membrane integrity (P<0.001), whereas DMSO affected sperm motility and membrane integrity (P<0.001). DMFA 2.5% yielded higher (P<0.001) values for sperm motility and membrane integrity. We concluded that Gent B improves in vitro post-thaw sperm quality of donkey spermatozoa, but the replacement of glycerol with 1% EG or 2.5% DMFA increased sperm protection against cryodamage. The use of DMSO for freezing donkey semen was unsuccessful and a toxic effect is suspected. These extenders should be included in the pre-freeze test for each donkey.

Supplemented stallion seminal plasma can improve impaired motility due to the dilution effect in chilled Asian elephant sperm

The dilution effect and effect of restoring seminal plasma (SP) proportion in diluted semen were determined in chilled Asian elephant sperm. Semen was collected from eight males, and samples with ≥30% motile sperm were used in the study. Tris-glucose-egg yolk extender (TE) was used for cooled storage at 4°C for 48 hr. In experiment 1 (n = 18), semen was diluted to 1:1, 1:3, 1:7 and 1:15 with TE (volume per volume). There were no significant changes in sperm viability and sperm with normal acrosome integrity among dilutions, but sperm motility and motility velocities were greater (p < .05) in the 1:1 dilution than those of the 1:7 and 1:15 dilutions at 48 hr of storage. In experiment 2, supplemented SP was derived from elephants and stallions. In experiment 2.1, diluted semen (1:7 dilution) was restored with SP to obtain a 1:2 proportion (n = 8). Sperm motility, viability and sperm with normal acrosome integrity were similar among treatments, but motility velocities were greater (p < .05) with stallion SP at 48 hr of storage. In experiment 2.2, diluted semen (1:15 dilution) was restored with SP to obtain a 1:3 proportion (n = 10). Sperm viability and sperm with normal acrosome integrity were similar among treatments at 48 hr of storage. However, sperm motility and motility velocities were greater (p < .05) with stallion SP than those of others. In conclusion, elephant sperm motility was affected by a dilution effect and restoration of SP proportion with stallion SP, but not with elephant SP, could improve motility in chilled highly diluted sperm.

Cryoprotective effect of glutamine, taurine, and proline on post-thaw semen quality and DNA integrity of donkey spermatozoa

This study was conducted to evaluate the effect of amino acid addition to semen on post-thaw quality of donkey spermatozoa. Eighteen ejaculates were pooled and divided into aliquots which were cryopreserved in Gent A^® containing 1% ethylene glycol (Gent-EG) and supplemented with 0 (as control), 20, 40, or 60 mM of glutamine, proline, or taurine. The greatest concentration (60 mM) of glutamine and taurine resulted in greater (P < 0.001) post-thaw sperm motility. Amino acid supplementation did not improve (P > 0.05) sperm morphology and membrane plasma integrity compared with the control samples. Whereas, improvement (P < 0.05) of acrosome integrity was observed with use of 60 mM glutamine. After thawing, there were no differences (P > 0.05) in the sperm DNA fragmentation index (sDFI) among treatments. The 60 mM glutamine and 40 mM taurine treatments, however, resulted in a reduction (P < 0.05) in sDFI values in the first 6 h of semen incubation, compared with the control samples. At 24 h, the sDFI values were less (P < 0.05) in all supplemented as compared with control samples, except for the 20 mM proline treatment group. In conclusion, supplementation of the Gent-EG extender with glutamine or taurine at 60 mM improved post-thaw donkey sperm quality. The addition of proline to the freezing extender, however, did not provide any significant enhancement in sperm quality, compared with the control group.

Effect of glutamine supplementation and replacement of tris-egg yolk based extender with defatted cow milk on spermatozoa quality after equilibration and thawing

AIM

The present study was designed to evaluate the effect of supplementation of glutamine and replacement of Tris-egg yolk (TE) based buffer with defatted cow milk on the spermatozoa quality after equilibration and thawing.

MATERIALS AND METHODS

Semen was collected from five Bhadawari bulls biweekly, and a total of 30 ejaculates were taken. The semen ejaculates were pooled and divided into three equal parts. The pooled semen was diluted by TE based extender (control), TE + glutamine (8 mM) (T1) and 50% TE + 50% deffated cow milk + glutamine (8 mM) (T2). At two stages viz. after equilibration and after 12 h of cryopreservation (thawed samples), progressive motility, percent live, and percent acrosomal damage of the spermatozoa was assessed.

RESULTS

Supplementation of glutamine improved (p<0.05) the spermatozoa quality with respect to the progressive motility, percent live and acrosomal damage both post-equilibration and post-thaw. T2 improved (p<0.05) the spermatozoa quality as compared to control, however; it was less (p<0.05) effective as compared T1 both post-equilibration and post-thaw.

CONCLUSION

From the results of present study it can be concluded that glutamine supplementation was effective in maintaining post-equilibration and post-thaw spermatozoa quality whereas defatted cow milk was not as effective as TE based buffer in the extender in improving the spermatozoa quality.