Factors influencing boar sperm cryosurvival1

Boar semen cryopreservation: State of the art, and international trade vision

Biosecurity is a major concern in the global pig production. The separation in time of semen collection, processing and insemination in the pig farm is a few days for chilled semen but it can be indefinite when using cryopreserved semen. Field fertility results of boar cryopreserved semen are close to chilled semen, which makes it a valuable resource for the establishment of semen genebanks, long-distance semen trade, and the implementation of other technologies such as the sex-sorted semen. But cryopreserved semen is far from being routine in pig farms. The most recent research efforts to facilitate its implementation include the use of additives before freezing, or in the thawing extender. Long-term preserved semen trade is a biosecurity challenge. To harmonize international trade of germplasm, the World Organization of Animal Health (WOAH) established a regulatory framework for all member countries. The present paper aims to review the latest advances of boar semen cryopreservation with special focus on the benefits of its inclusion as a routine tool in the pig industry. We also review recently reported field fertility results of cryopreserved semen, its international trade compared to chilled semen, and the regulatory framework involved. Boar cryopreserved semen is a valuable tool to control biosecurity risk, implement other technologies, and facilitate international trade. Research already demonstrated good field fertility results, but it still represents less than 0.1 % of the international trade. As boar cryopreserved semen gets closer to implementation, the correspondent authorities are reviewing the trade rules.

Study on the correlation of supplementation with L-citrulline on the gastrointestinal flora and semen antifreeze performance of ram

Introduction

Cryopreservation of semen can give full play to the reproductive advantages of male animals. However, in actual production, due to the poor frost resistance of sheep semen and the low conception rate, the promotion of sheep frozen semen is greatly hindered. Therefore, it is urgent to improve the frost resistance of semen to improve the quality of frozen semen. At present, most studies on improving the quality of frozen semen are based on the improvement of semen dilutions, and few studies on improving the freezing resistance of ram semen by feeding functional amino acids.

Methods

Therefore, 24 Turpan black rams were divided into high antifreeze group (HF) and a low antifreeze group (LF) Each of these groups was further randomly divided into control and experimental subgroups. The control subgroup was fed a basal diet, while the experimental subgroup received an additional 12 g/d of L-Cit supplementation based on the control group for a duration of 90 days.

Results

The results showed that Following L-Cit supplementation, the experimental group demonstrated significantly elevated sperm density and VSL (Velocity of straight line), T-AOC, GSH-Px, and NO levels in fresh semen compared to the control group (P < 0.01). After thawing, the experimental group exhibited significantly higher levels of T-AOC, GSH-Px, and NO compared to the control group (P < 0.01). Additionally, the HFT group, after thawing frozen semen, displayed significantly higher HK1 protein expression compared to the control group. The number of spermatogonia, spermatocytes, and sperm cells in the HFT group was significantly higher than that in the HFC group. Moreover, 16S rRNA sequence analysis showed that Candidatus_Saccharimonas, Staphylococcus, Weissella, succinivbrionaceae_UcG_002, and Quinella were significantly enriched in the rumen of the HFT group, while Ureaplasma was significantly enriched in the HFC group. In the duodenum, Clostridiales_bacterium_Firm_14, Butyrivibrio, and Prevotellaceae_NK3831_group were significantly enriched in the HFT group, whereas Desulfovibrio and Quinella were significantly enriched in the HFC group.

Discussion

Under the conditions employed in this study, L-Cit supplementation was found to enhance the intestinal flora composition in rams, thereby improving semen quality, enhancing the antifreeze performance of semen, and promoting the development of testicular spermatogenic cells.

Antifreeze protein type III addition to freezing extender comprehensively improves post-thaw sperm properties in Okinawan native Agu pig

Sperm cryopreservation often leads to physical cell damage through ice crystal formation. This study evaluates the improvements to freezing extender cryoprotective activity due to antifreeze protein (AFP) addition, which primarily acts on ice crystal formation, through investigating the post-thaw sperm properties of Okinawan native Agu pig. Six individual boar sperm samples were diluted with the freezing extender supplemented with 1 μg/mL of AFP I or AFP III and then subjected to cryopreservation. Treatment with AFP I during the freezing procedure had no improvement for any characteristics after thawing compared to untreated sperm. In contrast, the addition of AFP III to the freezing extender strongly increased sperm motility, mitochondria and cell membrane integrity, and the acrosomal proteolytic activity of frozen-thawed sperm in 5 of 6 individuals (P < 0.05). Furthermore, cryoinjury prevention by AFP III significantly enhanced sperm viability (by ATP content), and maintained DNA quality and in vitro sperm penetrability compared with AFP I treatment (P < 0.05). These findings demonstrate that AFP III addition to the freezing extender of boar sperm is more effective in maintaining sperm characteristics than the extender without AFP III or AFP I, despite individual differences in response.

Type I Diabetes in Zebrafish Reduces Sperm Quality and Increases Insulin and Glucose Transporter Transcripts

Type I diabetes is a prominent human pathology with increasing incidence in the population; however, its cause is still unknown. This disease promotes detrimental effects on reproduction, such as lower sperm motility and DNA integrity. Hence, the investigation of the underlying mechanisms of this metabolic disturbance in reproduction and its transgenerational consequences is of the utmost importance. The zebrafish is a useful model for this research considering its high homology with human genes as well as its fast generation and regeneration abilities. Therefore, we aimed to investigate sperm quality and genes relevant to diabetes in the spermatozoa of Tg(ins:nfsb-mCherry) zebrafish, a model for type I diabetes. Diabetic Tg(ins:nfsb-mCherry) males showed significantly higher expression of transcripts for insulin a (insa) and glucose transporter (slc2a2) compared to controls. Sperm obtained from the same treatment group showed significantly lower sperm motility, plasma membrane viability, and DNA integrity compared to that from the control group. Upon sperm cryopreservation, sperm freezability was reduced, which could be a consequence of poor initial sperm quality. Altogether, the data showed similar detrimental effects related to type I diabetes in zebrafish spermatozoa at the cellular and molecular levels. Therefore, our study validates the zebrafish model for type I diabetes research in germ cells.

Optimizing Bull Semen Cryopreservation Media Using Multivariate Statistics Approaches

Cryo-injury reduces post-thaw semen quality. Extender components play a protective role, but existing experimental approaches do not elucidate interactions among extender components, semen samples, and post-thaw quality. To identify optimal concentrations for 12 extender ingredients, we ran 122 experiments with an I-optimal completely random design using a large dataset from our previous study. We obtained a maximum predicted total motility of 70.56% from an I-optimal design and 73.75% from a Monte Carlo simulation. Individual bull variations were significant and interacted with extenders independently. 67% of bulls reliably preferred extender formulations to reach maximum motility. Multifactor analysis suggests that some antioxidants may offer superior protection over others. Partial least squares path modeling (PLS-PM) found the highest positive loadings for glutathione in the antioxidant class, glycerol in the CPA class, and fructose in the basic compounds class. The optimal ranges for milk, water, and ethylene glycol were extremely narrow. Egg yolk, cholesterol-loaded cyclodextrin, and nerve growth factor had medium-loading impacts. PLS-PM showed that CPA, osmoregulators, and basic components were the most efficient contributors to motility, while the antioxidant and extracellular protectant classes had less efficiency. Thus, ingredients, concentrations, and interactions of extender compounds are critical to extender formulation, especially when using multiple compounds with the same function.

Albumin (ALB) and protein disulfide isomerase family A member 4 (PDIA4) are novel markers to predict sperm freezability of Erhualian boar

The frozen semen of Erhualian pig can promote the continuous improvement of commercial pigs, but currently, frozen semen fails to satisfy the practical application requirement. Oxidative damage is one of the crucial factors affecting the quality of frozen semen; besides, there are individual differences in boar sperm freezability. Based on the previous analysis of the proteomic differences of Erhualian boar sperm with different freezability, two differentially abundant proteins (DAPs) in boar sperm, albumin (ALB) and protein disulfide isomerase family A member 4 (PDIA4), were selected as the research objects in the current study. It is assumed that redox-related proteins ALB and PDIA4 can be used as markers to predict Erhualian boar sperm freezability. We cryopreserved the semen of 14 Erhualian boars. According to the difference of frozen semen quality, boars with good and poor freezability ejaculates (GFE and PFE, n = 3) were selected respectively. The relative contents of ALB and PDIA4 in GFE and PFE were analyzed by Western blot, and the localization patterns of ALB and PDIA4 in pre-frozen and frozen-thawed sperm were detected by immunofluorescence. The results showed that the abundances of ALB and PDIA4 in GFE were significantly higher than PFE, and there was a significant correlation between the relative contents of ALB and PDIA4 and frozen-thawed sperm quality parameters. Additionally, the freezing process had no effect on the localization patterns of ALB and PDIA4 in spermatozoa. In conclusion, these results suggest that ALB and PDIA4 are related to boar sperm cryotolerance and may be used as novel freezability markers.

Advances in sperm cryopreservation in farm animals: Cattle, horse, pig and sheep

Sperm cryopreservation is one of the most important procedures in the development of biotechnologies for assisted reproduction. In some farm animals, the use of cryopreserved sperm has so many benefits for which relevance has become more evident in recent decades. Values for post-thaw sperm quality, however, are variable among species and within individuals of the same species. There is no standardized methodology for each of the stages of the cryopreservation procedure (andrological examination, semen collection, dilution, centrifugation, resuspension of the pellet with the freezing medium, packaging, freezing and post-thaw sperm evaluation), which also contributes to differences among studies. Cryotolerance markers of sperm and seminal plasma (SP) have been evaluated for prediction of ejaculate freezability. In addition, in previous research, there has been a focus on supplementing cryopreservation media with different substances, such as enzymatic and non-enzymatic antioxidants. In most studies, inclusion of these substances have led to improved post-thaw sperm quality and fertilizing capacity as a result of minimizing the adverse effects on sperm structure and function. Another approach is the use of different cryoprotectants. The aim with this review article is to provide an update on sperm cryopreservation in farm animals. The main detrimental effects of cryopreservation are described, including the negative repercussion on reproductive performance. Furthermore, the potential use of molecular biomarkers to predict sperm cryotolerance is discussed, as well as the addition of substances that can mitigate the harmful impact of freezing and thawing on sperm.

Extracellular vesicles in seminal fluid and effects on male reproduction. An overview in farm animals and pets

Extracellular vesicles (EVs) are lipid bilayer nanovesicles released by most functional cells to body fluids, containing bioactive molecules, mainly proteins, lipids, and nucleic acids having actions at target cells. The EVs have essential functions in cell-to-cell communication by regulating different biological processes in target cells. Fluids from the male reproductive tract, including seminal plasma, contain many extracellular vesicles (sEVs), which have been evaluated to a lesser extent than those of other body fluids, particularly in farm animals and pets. Results from the few studies that have been conducted indicated epithelial cells of the testis, epididymis, ampulla of ductus deferens and many accessory sex glands release sEVs mainly via apocrine mechanisms. The sEVs are morphologically heterogeneous and bind to functional cells of the male reproductive tract, spermatozoa, and cells of the functional tissues of the female reproductive tract after mating or insemination. The sEVs encapsulate proteins and miRNAs that modulate sperm functions and male fertility. The sEVs, therefore, could be important as reproductive biomarkers in breeding sires. Many of the current findings regarding sEV functions, however, need experimental confirmation. Further studies are particularly needed to characterize both membranes and contents of sEVs, as well as the interaction between sEVs and target cells (spermatozoa and functional cells of the internal female reproductive tract). A priority for conducting these studies is development of methods that can be standardized and that are scalable, cost-effective and time-saving for isolation of different subtypes of EVs present in the entire population of sEVs.

Hydroxytyrosol and resveratrol improves kinetic and flow cytometric parameters of cryopreserved bull semen with low cryotolerance

There is considerable interest in breeding programs to "rescue" semen with poor post-thaw fertility from bulls known as "bad freezers". We hypothesized that there may be an interaction between the post-thaw recovery of sperm and the efficacy of antioxidant addition to extenders. The current study assesses the effects of antioxidant additives hydroxytyrosol (HT) and resveratrol (RSV) on the post-thaw semen parameters in two groups of bulls classified as either high or low cryotolerant (i.e., "good" and "bad" freezers). Semen samples were collected from 40 bulls and processed in the extenders containing different concentrations of HT (experiment 1; 0, 25 and 50 µM) and RSV (experiment 2; 0.0, 0.01, 0.1 and 1 mM). In experiment 1, bulls in the low cryotolerance group had a significant improvement in post-thaw recovery at 25 µM and 50 µM (P < 0.05). These improvements were observed in motility and several cellular parameters. However, post-thaw semen quality in the high cryotolerance group was not significantly affected by the HT addition. In experiment 2, although RSV did not have any positive impact in high cryotolerance group, post-thaw recovery in the low cryotolerance bulls was significantly improved in 0.1 mM RSV. Oxidative stress markers in either high or low cryotolerance groups were not significantly changed by RSV addition (P > 0.05). It can be concluded that addition of optimized concentrations of HT and RSV to the extender could be a strategy for improving the post-thaw semen, especially in bulls with high genetic merit but low initial cryotolerance.

Optimization of the Thawing Protocol for Iberian Boar Sperm

Simple Summary

Limited attention is paid to sperm thawing protocols, and their study could be relevant to endangered species or breeds, especially for cryopreserved material present in the existing gene banks. The aim of this study was to determine the most optimal thawing protocol for Iberian boar sperm through testing different thawing rates and different modifications of the thawing extender. Based on the findings, the most optimal results were obtained thawing at 70 °C for 8 s with the inclusion of cyclodextrins loaded with cholesterol (CLC) in the extender, revealing the importance of adapting the thawing protocols.

Abstract

Thawing protocols have been barely studied, and their modifications may lead to a substantial improvement in post-thawing sperm quality, which could be of great relevance to existing sperm banks, such as those for Iberian pig breeds with varieties in danger of extinction. For that, the study aimed to evaluate different thawing rates and to evaluate modifications in the composition of the thawing extender (basic pH to 8–8.2, incorporation of cyclodextrins loaded with cholesterol [CLC] and the incorporation of ion chelators [EDTA and EGTA]). After thawing, overall sperm motility and kinematic parameters, acrosome status and sperm membrane integrity were evaluated. The most optimal results were obtained with the thawing rate reaching 70 °C for 8 s with the inclusion of 12.5 mg of CLC/500 × 10⁶ spermatozoa in the thawing extender, which showed an improvement compared to the control at 70 °C. In conclusion, to adapt the thawing conditions may be relevant, especially for endangered species or breeds such as some varieties of Iberian pig, since this process could also be used in samples cryopreserved in gene banks.

Effect of Sperm Cryopreservation in Farm Animals Using Nanotechnology

Sperm cryopreservation is one of the sublime biotechnologies for assisted reproduction. In recent decades, there has been an increasing trend in the use of preserved semen. Post-thaw semen quality and values vary among animals of the same species. Similarly, there are species-specific variations in sperm morphology, i.e., sperm head, kinetic properties, plasma membrane integrity, and freezability. Similarly, the viability of sperm varies in the female reproductive tract, i.e., from a few hours (in cattle) to several days (in chicken). Various steps of sperm cryopreservation, i.e., male health examination, semen collection, dilution, semen centrifugation, pre- and post-thaw semen quality evaluation, lack standardized methodology, that result in differences in opinions. Assisted reproductive technologies (ART), including sperm preservation, are not applied to the same extent in commercial poultry species as in mammalian species for management and economic reasons. Sperm preservation requires a reduction in physiological metabolism by extending the viable duration of the gametes. Physiologically and morphologically, spermatozoa are unique in structure and function to deliver paternal DNA and activate oocytes after fertilization. Variations in semen and sperm composition account for better handling of semen, which can aid in improved fertility. This review aims to provide an update on sperm cryopreservation in farm animals.

Addition of l-carnitine to the freezing extender improves post-thaw sperm quality of Okinawan native Agu pig

The objective of the present study was to establish whether the addition of l-carnitine (LC), which exhibits antioxidant activity, to the freezing extender improves the quality of cryopreserved Okinawan native Agu pig sperm. Ejaculated sperm frozen in an extender supplemented with 0, 1, 2.5, or 5 mM LC was thawed, and the integrities of mitochondria and the plasmalemma and other sperm characteristics were evaluated. The treatment with different concentrations of LC effectively improved sperm motility, mitochondrial and plasmalemmal integrities, and the proteolytic activity of acrosomal contents after freeze-thawing (P < 0.05). The proportion of post-thaw sperm possessing intact mitochondria and plasmalemma and higher proteolytic activity of acrosomal contents was markedly higher among sperm frozen in the presence of 2.5 mM LC than among sperm frozen in the extender without LC (P < 0.05). Furthermore, although the addition of LC to the freezing extender had no effect on disturbance of DNA damage and caspase activity, sperm treated with 2.5 mM LC during freezing exhibited significantly higher penetrability into matured oocytes in vitro than untreated sperm. Collectively, these results indicate that the addition of LC to the freezing extender effectively improved the post-thaw quality of Agu pig sperm by preventing mitochondrial dysfunction caused by oxidative stress during cryopreservation.

Spermatozoa and seminal plasma small extracellular vesicles miRNAs as biomarkers of boar semen cryotolerance

Freeze boar semen is still the biggest challenge for the swine industry due to the high cold shock sensitivity of boar sperm cells and the variance of post-thaw results among individuals and ejaculates from the same boar. To solve this problem, we investigate if miRNAs present in sperm cells and small extracellular vesicles (EVs) from seminal plasma of raw boar ejaculates can predict high-quality ejaculates after underwent the freeze-thaw process. For this, we obtained miRNAs samples of sperm cells and EVs from raw seminal plasma from 27 ejaculates before the cryopreservation process. Two groups with different freezability considering the analysis post-thaw of structure and sperm functionality were formed: High freezability (HF; n = 04) and low freezability (LF; n = 04). That done, we investigated the miRNAs profile of sperm cells and EVs from seminal plasma in both groups. Three miRNAs were differently abundant in LF ejaculates, being the ssc-miR-503 found in higher levels in sperm cells (P < 0.10). The ssc-miR-130a and ssc-miR-9 most abundant in EVs from seminal plasma (P < 0.10), in LF ejaculates. Through enrichment analysis, it was possible to verify that these miRNAs could be performing modifications in the development of male germ cells and in the production of energy to spermatozoa to maintain their viability and functionality. Therefore, we can demonstrate that ssc-miR-503, ssc-miR-130a, and ssc-miR-9 are related to low sperm cryotolerance in boars semen. So those miRNAs can be used as a biomarker to predict their low ability to tolerate the cryopreservation process.

Evaluation of Microscopic, Flow Cytometric, and Oxidative Parameters of the Frozen-Thawed Bull Sperm in a Freezing Extender Containing Myo-Inositol

Introduction: This research was conducted to assess the effect of myo-inositol (MYO) in the freezing extender on the semen quality and oxidative stress parameters of frozen-thawed bull sperm. Materials and Methods: Semen samples were obtained from four bulls (n = 24, six ejaculates per bull), twice a week, and diluted into four equal aliquots in freezing extenders containing different concentrations of MYO (0, 2, 3, and 4 mg/mL). After a freezing/thawing process, velocity parameters, plasma membrane integrity, apoptosis status, malondialdehyde level, and oxidative stress parameters were assessed. Results: Supplementation of freezing extender with 3 mg/mL MYO resulted in higher rapid motility (62.22% ± 2.63%), progressive motility (77.45% ± 2.65%), viability (78% ± 0.91%), plasma membrane integrity (86 ± 0.85), catalase (20.03 ± 0.39 U/mL) activity, and lower significance of lipid peroxidation (3.60 ± 0.15 nmol/dL) than those of the control group (p < 0.05). A significantly lower percentage of normal morphology and intact acrosomes were observed for frozen-thawed semen in the extender supplemented with 4 mg/mL MYO than those of the control group (p < 0.05). Freezing of the sperm in the extender containing 3 mg/mL of MYO leads to a higher percentage of live cells (38.3 ± 2.76). Beat-cross-frequency, amplitude of lateral head displacement, linearity, total antioxidant capacity, total peroxidase activity, early apoptotic status, and superoxide dismutase activities were not affected by MYO levels in the extenders (p > 0.05). Conclusion: The findings of this study suggest that the supplementation of the freezing extender with 3 mg/mL MYO resulted in a higher quality of frozen-thawed bull sperm.

Post-Thaw Sperm Quality and Functionality in the Autochthonous Pig Breed Gochu Asturcelta

Simple Summary

Genetic resource banks were created to preserve the genetic material of endangered, rare, valuable individuals or genetically relevant breeds. Sperm cryopreservation is a practical and widespread strategy to preserve these genetic materials. This study aimed to characterize the frozen-thawed sperm of the native pig breed Gochu Asturcelta, considering the effects of boar age and season of semen collection on post-thaw sperm quality. We found that the boar age did not have a significant effect on the sperm parameters assessed. However, the season significantly affected many of these parameters (motility, viability, acrosomal status, mitochondrial activity). In general, sperm samples collected in spring and summer showed higher quality post-thawing, the lowest in winter. Our findings demonstrated that the post-thawing sperm quality of Gochu Asturcelta was in the range of results for commercial breeds, bringing a good prospect for the use of assisted reproductive technologies in this local breed.

Abstract

Genetic resource banks (GRB) preserve the genetic material of endangered, valuable individuals or genetically relevant breeds. Semen cryopreservation is a crucial technique to reach these goals. Thus, we aimed to assess the sperm parameters of semen doses from the native pig breed Gochu Asturcelta stored at the GRB of Principado de Asturias (GRB-PA, Gijón, Spain), focusing on intrinsic and extrinsic (boar, season) factors. Two straws per boar (n = 18, 8–71 months of age) were thawed, pooled, and assessed after 30 and 150 min at 37 °C by CASA (computer-assisted sperm analysis system; motility and kinematic parameters) and flow cytometry (viability, acrosomal status, mitochondrial activity, apoptosis, reactive oxygen species, and chromatin status). The effects of age, incubation, and season on post-thawing quality were determined using linear mixed-effects models. Parameters were on the range for commercial boar breeds, with chromatin status (SCSA: fragmentation and immaturity) being excellent. Incubation decreased sperm quality and functionality. The boar age did not have a significant effect (p > 0.05), but the between-boar variability was significant (p < 0.001). The season significantly affected many parameters (motility, kinematics, viability, acrosomal status, mitochondrial activity), especially after 150 min of incubation. In general, samples collected in spring and summer showed higher quality post-thawing, the lowest in winter. In conclusion, the sperm doses from the Gochu Asturcelta breed stored at the GRB-PA showed excellent chromatin status and acceptable characteristics after thawing. Therefore, boar and seasonal variability in this autochthonous breed could be relevant for cryobank management.

Cold-Shock Test Is a Practical Method for Selecting Boar Ejaculates Yielding Appropriate Seminal Plasma for Post-Thawing Supplementation

Simple Summary

The pig industry routinely uses artificial insemination with refrigerated semen. Cryopreserved semen has many advantages, but it is not widely used, partly because of unreliable results. The supplementation with seminal plasma (SP) could improve these results, but this fluid also presents variability. We evaluated if a simple cold-shock test (CST) could allow to easily identify the most suitable ejaculates for obtaining SP. Therefore, we tested 63 ejaculates, obtaining SP from the 4 showing higher quality (SPr, cold-shock-resistant) and lower quality (SPs, cold-shock-sensitive) after the CST. SPs and SPr pools supplemented thawed semen (20% SP) from six different boars, incubating at 37 °C and analyzing at times 0, 2, and 4 h. SPr was able to improve post-thawing sperm motility while maintaining viability. SPs had a similar but lower effect. SP in general seemed to stimulate sperm physiology, however decreasing membrane stability, acrosomal integrity, and disulfide bridges in the chromatin. This study supports the suitability of SP for improving thawed semen, with CST-selected ejaculates as preferable for this aim. Artificial insemination trials with thawed semen supplemented with SPr and SPs must validate the practical application of CST.

Abstract

Artificial insemination (AI) with cryopreserved semen is still unreliable for extensive pig industry application. Adding seminal plasma (SP) could improve post-thawing quality, but its suitability could vary. We applied a simple cold-shock test (CST, 5 min at 0 °C) on neat semen for classifying ejaculates (n = 63) as resistant or sensitive, obtaining two SP pools (CST-resistant: SPr, sensitive: SPs). Subsequently, frozen/thawed spermatozoa from six boars were incubated (37 °C) in MR-A® extender (control), 20% SPr, or 20% SPs, and analyzed at 0, 2, and 4 h. SP improved total and progressive motility, with a higher effect for SPr and STR (p < 0.05), decreasing kinematic parameters VCL and VAP, ALH, and BCF. Sperm viability was unaffected. SP increased apoptotic and membrane disorder ratios, and acrosomal damage, not affecting the chromatin structure (DNA fragmentation and immaturity by SCSA), protamination (CMA3), or disulfide levels (mBBr). However, the proportion of spermatozoa with elevated free thiols (disulfide bridges reduction) significantly increased. Results support a stimulatory role of SP on thawed semen, with additional benefits from SPr. The effect of SP and especially SPr after AI should be tested since CST could be a practical test for selecting suitable ejaculates in AI centers.

Achievements and future perspectives of embryo transfer technology in pigs

Commercial embryo transfer (ET) has unprecedented productive and economic implications for the pig sector. However, pig ET has been considered utopian for decades mainly because of the requirements of surgical techniques for embryo collection and embryo deposition into recipients, alongside challenges to preserve embryos. This situation has drastically changed in the last decade since the current technology allows non-surgical ET and short- and long-term embryo preservation. Here, we provide a brief review of the improvements in porcine ET achieved by our laboratory in the past 20 years. This review includes several aspects of non-surgical ET technology and different issues affecting ET programmes and embryo preservation systems. The future perspectives of ET technology are also considered. We will refer only to embryos produced in vivo since they are the only type of embryos with possible short-term use in pig production.

Proteomics in fresh and preserved pig semen: Recent achievements and future challenges

Proteins in semen, either in spermatozoa (SPZ) or seminal plasma (SP), are directly involved in molecular processes and biological pathways regulating sperm function, including fertilizing ability. Therefore, semen proteins are candidates of choice for biomarkers discovery for fertility and for sperm (dys)function. Mass spectrometry (MS)-based proteomics has opened up a new era for characterizing and quantifying the protein profile of SP and SPZ, as well as for unveiling the complex protein interactions involved in the activation of sperm functionality. This article overviews existing literature on MS-based proteomics regarding porcine semen, with a specific focus on the potential practical application of the results achieved so far. The weaknesses of current studies and the perspectives for future research in MS-based pig semen proteomics are also addressed.

Transcriptome analysis of boar spermatozoa with different freezability using RNA-Seq

Semen freezability is associated with genetic markers, and there is a diverse set of sperm transcripts that have been attributed to various cellular functions. RNA-Seq was performed to compare the transcript profiles of spermatozoa from boars with different semen freezability. We examined ejaculates from the Polish large white (PLW) boars that were classified as having good and poor semen freezability (GSF and PSF, respectively; n = 3 boars per group) by assessing post-thaw motility characteristics, mitochondrial membrane potential, plasma membrane and acrosome integrity. Total RNA was isolated from fresh spermatozoa from boars of the GSF and PSF groups and subjected to RNA-Seq (Illumina NextSeq 500 platform). Transcript abundance was assessed with the DESeq2, DESeq, and EdgeR Bioconductor R packages, and varying numbers of differentially expressed gene (DEG) transcripts were detected in the spermatozoa of each boar. Using RNA-Seq, we identified several genes associated with inflammation and apoptosis (FOS, NFATC3, ITGAL, EAF2 and ZDHHC14), spermatogenesis (FGF-14 and BAMBI), autophagy (RAB33B), protein phosphorylation (PTPRU and PTPN2) and energy metabolism (ND6 and ACADM) that were predominantly up-regulated in poor freezability ejaculates. Quantitative reverse transcription polymerase chain reaction (RT-qPCR) validated the transcript expression levels detected by RNA-Seq and thus confirmed the reliability of this technique. Subsequent validation with western blotting showed that the expression of three proteins was in accordance with the transcript abundance. Overall, we demonstrated that the up-regulation of the DEG transcripts in spermatozoa was associated with poor semen freezability. We suggest that spermatozoa transcriptome profiling provides a foundation to further elucidate the relevance of sperm-related transcripts on cryo-survival. The sperm-related transcripts, namely FOS, NFATC3, EAF2, BAMBI, PTPRU, PTPN2, ND6 and ACADM, are potential markers for predicting the freezability of boar semen.

Relative content of Niemann-Pick C2 protein (NPC2) in seminal plasma, but not that of spermadhesin AQN-1, is related to boar sperm cryotolerance

Variation between and within boar ejaculates in terms of their ability to withstand freeze-thawing is a limitation for sperm cryopreservation. Consequently, searching for freezability markers not only in sperm but also in seminal plasma (SP) is imperative. The present study aimed to evaluate the relationship between cholesterol content, relative levels of NPC2 and AQN-1 at two different holding times (0 h: HT0 and 24 h: HT24) at 17 °C, and boar sperm freezability. Forty-five ejaculates were cryopreserved and subsequently classified as of good (GFE) or poor (PFE) freezability according to their post-thaw sperm viability and total motility. Prior to cryopreservation, relative abundances of two SP proteins (NPC2 and AQN-1) and cholesterol content in sperm and SP were determined through immunoblotting and colorimetric methods, respectively. These determinations were made after ejaculation (HT0) and after 24 h of storage at 17 °C (HT24). Two bands for NPC2 protein (16 kDa and 19 kDa) were identified. Relative amounts of the 16 kDa-band were significantly (P < 0.05) higher in poor (PFE) than in good (GFE) freezability ejaculates both at HT0 and HT24, whereas those of the 19 kDa-band were significantly (P < 0.05) higher in PFE than in GFE at HT24 only. In the case of AQN-1, no significant differences between GFE and PFE were observed. In addition, no variations in the cholesterol content of sperm and SP were observed either between HT0 and HT24 or between GFE and PFE. We can conclude that the content of two NPC2 isoforms in SP, but not of that of spermadhesin AQN-1, may be involved in the sperm resilience to withstand freeze-thawing procedures and may predict ejaculate freezability. While a possible mechanism through which NPC2 during HT could affect boar sperm cryotolerance is suggested to be related to its ability to bind the plasma membrane cholesterol, further research is warranted.

A new test based on the hypotonic resistance and functional competence to evaluate the sperm quality, cryotolerance and in vitro fertilizing ability in pigs

The present work aimed at setting a new test of boar sperm functional competence (SFCt) to determine the association with sperm in vitro fertilizing ability and cryotolerance. Three independent experiments were conducted. In the first experiment, a gage repeatability and reproducibility (R&R) study was carried out to determine the reliability of the SFCt. Following this, 1565 ejaculates were clustered on the basis of sperm membrane and acrosome integrity, total motility, morphology and membrane functional integrity. Two groups were obtained and their SFCt values were compared. In the second experiment, 45 ejaculates were classified into two groups based on cleavage rates after in vitro fertilization and the SFCt outcomes of the two groups were examined. In the third experiment, 45 ejaculates were cryopreserved and classified as with good (GFE) or poor freezability (PFE) based on their post-thaw sperm membrane integrity and total motility; the SFCt outcomes in liquid-stored semen were also compared. ROC curves were used to address the accuracy of the SFCt in each experiment. In the R&R study, the greater variability of the study was attributed to the differences between ejaculates (97.61%); SFCt values were significantly (P < 0.01) higher in the good than in the poor sperm quality group. Ejaculates with high cleavage rates showed significantly (P < 0.05) higher SFCt values than ejaculates with low cleavage rates. SFCt values of GFE before cryopreservation were significantly (P < 0.05) higher than those of PFE. The SFCt had a fair discriminatory value in all experiments. In conclusion, the SFCt is a useful and reliable test to evaluate the sperm quality and is also related to the sperm resilience to withstand freeze-thawing procedures. However, further studies evaluating blastocyst formation and AI trials with a large number of boars are needed to confirm the accuracy of this test.

Treatment of boar sperm with nanoparticles for improved fertility

Continuous progress in nanoscience has allowed the synthesis of various nanoscale particles, known as nanoparticles or nanomaterials which, by harnessing unique physico-chemical properties, are crucial for multiple bio-applications. Despite the revealed toxicity (nanotoxicity) of nanoparticles in various in vitro and in vivo studies, their careful design for biocompatibility and effective interactions with single-celled and multi-cellular organisms has permitted their use in several fields of research and biomedicine. The various nanoparticles synthesized and applied in the veterinary sciences, including reproductive biology, have shown potential to influence routine practices in animal production systems. These include post-collection manipulation of semen and the protection of high-quality spermatozoa to extend their preservation, and to improve sperm-related biotechnologies such as sperm-mediated gene transfer, sperm sorting, sex-sorting, and cryopreservation. Therefore, the application of nanotechnology-based tools to semen may enhance assisted reproductive technologies for biomedical applications and improve economic productivity for farmers. Here, we review the efficacy of available techniques and emerging tools of nanotechnology that might be useful for further selection of high quality boar spermatozoa and productivity improvement.

Use of the ACP® and BTS extenders for cooling at 15°C white-lipped peccary (Tayassu pecari) semen

ABSTRACT: Knowledge about reproduction of white-lipped peccary is of great importance to assist with the conservation of this species and enable its rational use in captivity. This study aimed to evaluate the effect of ACP-103®, ACP-116® and BTS semen extenders on sperm viability during cooling of Tayassu pecari semen. Five ejaculates from four adult males were chilled. The animals were submitted to the protocols of sedation and anesthesia for semen collection by the electroejaculation method. After collection, the semen was macro- and microscopically assessed and diluted to reach 35x106 spermatozoa/mL in each of the three different extenders tested. The fresh-extended semen was packed in a BotuFLEX® thermal box to keep samples at 15°C for 24 hours. After cooling, the following semen parameters were analyzed: sperm motility, functional and structural integrity of sperm membranes, mitochondrial activity, chromatin condensation, and the thermoresistance test was performed. The parameters sperm motility, structural and functional integrity of sperm membranes, mitochondrial activity, and chromatin condensation were preserved after use of the extenders tested, and were similar to those of in natura semen (p>0.05). Curvilinear velocity (VCL) (p<0.05) was the only parameter with reduced values after cooling regardless of the extender used. The percentage of sperm with normal morphology was greater in samples cooled using the BTS extender (p<0.05). The ACP-103®, ACP-116® and BTS extenders can be used for the cooling and preservation of white-lipped peccary semen at 15°C for 24 hours.

Cryopreservation Differentially Alters the Proteome of Epididymal and Ejaculated Pig Spermatozoa

Cryopreservation induces differential remodeling of the proteome in mammalian spermatozoa. How these proteome changes relate to the loss of sperm function during cryopreservation remains unsolved. The present study aimed to clarify this issue evaluating differential changes in the proteome of fresh and frozen-thawed pig spermatozoa retrieved from the cauda epididymis and the ejaculate of the same boars, with clear differences in cryotolerance. Spermatozoa were collected from 10 healthy, sexually mature, and fertile boars, and cryopreserved using a standard 0.5 mL-straw protocol. Total and progressive motility, viability, and mitochondria membrane potential were higher and membrane fluidity and reactive oxygen species generation lower in frozen-thawed (FT) epididymal than ejaculated spermatozoa. Quantitative proteomics of fresh and FT spermatozoa were analyzed using a LC-ESI-MS/MS-based Sequential Window Acquisition of All Theoretical Spectra approach. Cryopreservation quantitatively altered more proteins in ejaculated than cauda epididymal spermatozoa. Differential protein-protein networks highlighted a set of proteins quantitatively altered in ejaculated spermatozoa, directly involved in mitochondrial functionality which would explain why ejaculated spermatozoa deteriorate during cryopreservation.

High pre-freezing sperm dilution improves monospermy without affecting the penetration rate in porcine IVF

The high incidence of polyspermy is still an unresolved problem for the production of in vitro-produced porcine embryos. In this work, we modified the usual sperm processing sequence for in vitro fertilization (IVF), and the spermatozoa from four boars were frozen directly at a low sperm concentration of 20 × 10⁶ sperm/mL (high pre-freezing sperm dilution group; F20), thawed and processed for IVF in three replicates. Spermatozoa from the same boars frozen at a conventional concentration (1000 × 10⁶ sperm/mL) were used as the control group. The post-thaw sperm quality evaluation demonstrated that despite there being no differences in the percentage of motile spermatozoa between groups, the proportion of live spermatozoa with intact acrosomes was significantly higher in the F20 group than in the control. The in vitro penetration rate was also similar between groups; however, the co-incubation of oocytes with F20 sperm increased monospermy, IVF efficiency, cleavage rate and the efficiency of blastocyst formation compared with the results for oocytes co-incubated with control spermatozoa. These results indicate, for the first time, that a high pre-freezing sperm dilution increases monospermy without affecting penetration rates, thereby increasing blastocyst formation.

A comparative study of effects of different freezing methods on sperm quality, DNA integrity and membrane protein of cryopreserved boar semen*

The present study determined the effects of conventional, and controlled freezing method adopting three freezing rates, viz. 20°C, 40°C and 60°C/min on quality of sperm (motility, viability and plasma membrane integrity), DNA integrity and plasma membrane protein profile of cryopreserved boar semen. Sixty sperm-rich fractions of ejaculates from six boars were utilized for freezing of semen with different freezing methods in lactose-egg yolk glycerol extender. Semen samples were evaluated for sperm motility, viability (Propidium Iodide assay), functional integrity of plasma membrane (HOST), DNA integrity (Acridine Orange stain) and plasma membrane protein profile (SDSPAGE) after equilibration and after freezing. The results revealed that the post thaw sperm motility, sperm viability, and plasma membrane integrity (HOST-reacted) were significantly higher in all the three controlled freezing methods (20°C, 40°C and 60°C/min) as compared to that in conventional method. In addition, the number of sperm plasma membrane protein loss was less in controlled freezing methods as compared to that in conventional freezing. However, the post thaw sperm DNA integrity did not influence by difference in freezing methods. No significant difference on the post thaw sperm characteristics was recorded among the three controlled freezing rates. All the sperm parameters assessed declined significantly after freezing as compared to that after equilibration irrespective of freezing method employed. In conclusion, controlled freezing methods conferred better post thaw sperm quality as compared to conventional method, and thus the freezing rates of either 20, 40 or 60°C/min could provide better freezability of boar semen.

The use of ultrasonography in the reproductive evaluation of boars

The objective was to study the use of ultrasound as a complementary test in the breeding soundness evaluation in male pigs and study the pattern of echogenicity of the testicular parenchyma in boars of different racial groups. Twenty-six adult boars from four different racial groups were used, 10 from the Piau breed (group 1), four from the commercial and finishing group (group 2), six Pietrain breed (group 3) and six from the Duroc breed (group 4). All animals were evaluated for breeding soundness evaluation and the ultrasound examination of the testicles. The groups of animals that were evaluated showed no difference in the main semen parameters that were evaluated, except for the sperm volume, concentration of the ejaculated sperm and the supravital staining; the lowest figures were for the animals from the Piau breed (group 1). In relation to the testicular biometrics, Duroc animals (group 4) had a greater scrotal width compared to the other groups. But when we assessed the intensity of pixels of the testicles, there was a difference between groups. The groups 2 (finishing animals), 3 (Pietrain) and 4 had no difference between themselves. Group 3 had greater pixel intensity in relation to group 1. Of the 26 animals studied, five showed an abnormality during ultrasound evaluation, like hydrocele, hyperechoic mass in the testicular parenchyma, cyst in the head of the epididymis and the presence of fluid in the head and tail of the epididymis. The various animal groups studied did not differ in the principal reproductive parameters evaluated, showing that despite the great variability of reproductive traits between breeds and within the same breed, the breeding soundness evaluation, the more complete it is, is essential for the selection of breeders and the ultrasonography of the reproductive system becomes an important addition in this examination.

Variation in seminal plasma alters the ability of ram spermatozoa to survive cryopreservation

Variation in the effect of seminal plasma on sperm function and fertility has been hypothesised to be due to differences between males and their seminal plasma composition. The freezing resilience of individual rams (n=17) was investigated to characterise inter-male variation. This was determined by measuring the degree of change in motility induced by cryopreservation (Experiment 1). Experiment 2 examined the effect of pooled seminal plasma from rams identified as having high or low resilience to freezing on the cryosurvival of washed spermatozoa from either high (n=3) or low (n=3) sperm freezing resilience rams. Immediately after thawing and throughout the incubation period (0-4h), spermatozoa from high-resilience rams frozen with high-resilience seminal plasma demonstrated superior motility to spermatozoa from high-resilience rams frozen with low-resilience seminal plasma (P<0.001). Similarly, spermatozoa from low-resilience rams frozen with high-resilience seminal plasma exhibited higher motility than spermatozoa from low-resilience rams frozen with low-resilience seminal plasma immediately after thawing (0h; P<0.001). The present study shows that variation in freezing resilience of ram spermatozoa is related to the source and composition of the seminal plasma.

Effect of boar ejaculate fraction, extender type and time of storage on quality of spermatozoa

The aim of this study was to investigate the effect the sperm-rich fraction (F1) and the post-F1 fraction (F2) on the quality of boar spermatozoa stored in a liquid state. Ejaculates were collected from three Polish Landrace boars. Each ejaculate fraction was diluted with BTS short-term extender and Safe-Cell Plus (SCP) long-term extender and stored for seven days (D1-D7) at 17°C. Analyses included sperm motility parameters, normal apical ridge (NAR) acrosomes and plasma membrane integrity (PMI). Prior to the dilution of fractions, marked changes (p<0.05) were noted between F1 and F2 in progressive motility (PMOT), velocity average pathway (VAP) and velocity straight line (VCL). After the ejaculate was diluted, the type of fraction and type of extender significantly affected (p<0.05) PMOT, being markedly higher (p<0.05) for F1 extended in BTS. No marked changes (p<0.05) were observed between F1 and F2 extended in SCP for any of the analyzed sperm quality parameters during seven days of storage. Significantly higher (p<0.05) values of sperm quality parameters were noted in F1 compared with F2 for BTS on D7 of storage. The results of the four-way ANOVA analysis indicate that boar, fraction of ejaculate, extender type and day of storage had significant effects on the quality of boar stored spermatozoa. The F1 was characterised by higher quality of spermatozoa during storage in comparison with F2 in the short-term extender. Using the long-term extender containing the proteins allowed for a better application of F2, which could be important for the pig industry.

Relationship between HSP90a, NPC2 and L-PGDS proteins to boar semen freezability

BACKGROUND

The purpose of this study was to determine the association of three proteins involved in sperm function on the freezability of porcine semen: the heat shock protein 90 alpha (HSP90a), the Niemann-Pick disease type C2 protein (NPC2), and lipocalin-type prostaglandin D synthase (L-PGDS). Six adult boars (each boar was ejaculated three times, 18 in total) were classified by freezability based on the percentage of functionally competent sperm. The male semen with highest freezability (MHF) and the male semen with lowest freezability (MLF) were centrifuged immediately after collection to separate seminal plasma and spermatozoa to make four possible combinations of these two components and to incubate them for 3 h, adjusting the temperature to 17 °C, to freeze them afterwards. The quantification of proteins was performed in two stages: at zero and at 3 h after incubation of the four combinations.

RESULTS

The spermatozoa × incubation time (IT) interaction only had effect (P < 0.01) on HSP90a levels; this protein increased in seminal plasma, after 3 h of incubation, in larger quantity (P < 0.05) in combinations with MLF spermatozoa. In relation with the NPC2 protein, two isoforms of 16 and 19 kDa were identified. The 19 kDa isoform was affected (P < 0.01) only by the seminal plasma × IT interaction, with superior values (P < 0.01) both at zero and three hours of incubation, in the combinations with MHF seminal plasma; and 16 kDa isoform was affected (P < 0.01) only by the IT with reduction after 3 h of incubation. The levels of L-PGDS was affected (P < 0.01) only by the spermatozoa × IT interaction, which reduced (P < 0.01) in combinations with MLF spermatozoa after 3 h of incubation.

CONCLUSIONS

It is possible to consider that the three proteins evaluated were associated with freezability of boar semen due, especially, to the fact that mixtures with MLF spermatozoa showed greater increase levels of the HSP90a protein and reduction of L-PGDS in plasma. In addition, the seminal plasma of MHF had higher concentration of the NPC2 of 19 kDa protein, which was reduced by incubating with MHF spermatozoa.

The effect of dietary supplementation of algae rich in docosahexaenoic acid on boar fertility

The objective of this study was to assess the effects of dietary supplementation of a commercial algal product rich in docosahexaenoic acid (DHA) on boar fertility as assessed in vitro and in vivo. Boars were fed one of three experimental diets for 19 weeks: (i) Control (Ctl) diet (n = 31), (ii) Ctl diet plus 75g All-G-Rich per day (n = 31) or (iii) Ctl diet plus 150g All-G-Rich per day (n = 30). Parameters assessed were (i) raw semen quality; volume, sperm concentration, total motility and morphology (ii) liquid semen quality; progressive motility, viability, hypotonic resistance and acrosomal integrity (iii) frozen-thawed semen quality; motility, thermal stress, viability, membrane fluidity and mitochondrial activity (iv) sperm and seminal plasma (SP) fatty acid composition (FAC) (v) total antioxidant capacity (TAC) of SP and (vi) farrowing rates and litter sizes of sows (n = 1158) inseminated with liquid semen. Boars consuming 75g All-G-Rich had a larger semen volume (P < 0.05) and a higher total sperm number (P < 0.01) than the Ctl treatment, however, there was no effect of treatment on any other semen quality parameter (P > 0.05). There was no effect of dietary treatment on the FAC and TAC of SP or on farrowing rate and litter size (P > 0.05). There was an effect of dietary treatment on the FAC of sperm, represented by an 1.72 and 1.60 fold increase in the DHA content for 75 and 150g treatments, respectively, compared to the Ctl treatment. In conclusion, a significant increase in semen volume and total sperm number in boars supplemented 75g All-G-Rich daily, resulted in an increase in production of 3 to 4 more doses per ejaculate, thus, indicating that the feeding regime described within this study has the potential for increasing the output of boar studs.

The benefits of cooling boar semen in long-term extenders prior to cryopreservation on sperm quality characteristics

This study investigated the effects of long-term extenders on post-thaw sperm quality characteristics following different holding times (HT) of boar semen at 17 and 10°C. Sperm-rich fractions, collected from five boars, were diluted in Androhep(®) Plus (AHP), Androstar(®) Plus (ASP), Safecell(®) Plus and TRIXcell(®) Plus (TCP) extenders. The extended semen samples were held for 2 hr at 17°C (HT 1) and additionally for 24 hr at 10°C (HT 2), after they were evaluated and frozen. CASA sperm motility and motion patterns, mitochondrial membrane potential (MMP), plasma membrane integrity (PMI) and normal apical ridge (NAR) acrosome integrity were assessed in the pre-freeze and frozen-thawed semen. The Vybrant Apoptosis Assay Kit was used to analyse the proportions of viable and plasma membrane apoptotic-like changes in spermatozoa. Results indicated that boar variability, extender and HT significantly affected the sperm quality characteristics, particularly after freezing-thawing. Differences in the pre-freeze semen were more marked in the sperm motion patterns between the HTs. Pre-freeze semen in HT 2 showed significantly higher VCL and VAP, whereas no marked effects were observed in the sperm membrane integrity and viability (YO-PRO-1(-) /PI(-) ) among the extenders. Post-thaw sperm TMOT and PMOT were significantly higher in the AHP and ASP extenders of HT 2 group, whereas VSL, VCL and VAP were markedly lower in the TCP extender. Furthermore, spermatozoa from the AHP- and ASP-extended semen of HT 2 group were characterized by higher MMP, PMI and NAR acrosome integrity following freezing-thawing. In most of the extenders, the incidence of frozen-thawed spermatozoa with apoptotic-like changes was greater in HT 1. The findings of this study indicate that holding of boar semen at 10°C for 24 hr in long-term preservation extenders modulates post-thaw sperm quality characteristics in an extender-dependent manner. These results will further contribute to the improvement in the cryopreservation technology of boar semen.

Development of a sperm cryopreservation protocol for the Argentine black and white tegu (Tupinambis merianae)

Of the 934 lizard species evaluated by the International Union for the Conservation of Nature (IUCN), at least one-third is threatened with extinction. However, there are no reports of semen cryopreservation efforts for lizards. Invasive Argentine black and white tegus were captured in the Florida Everglades, and sperm was collected postmortem. Initial motility score (IMS; % motile × speed of progression² × 100), plasma membrane integrity (IPL), and acrosome integrity (IAC) were recorded. Sperm was diluted in TEST-yolk buffer with a final glycerol or dimethylsulfoxide (DMSO)concentration of 8%, 12%, or 16%, and frozen at 0.3 °C, 1.0 °C, or 6.3 °C/min. At thaw, all variables were expressed as the percentage of initial (%IMS, %IPL, and %IAC). The 0.3 °C freeze rate was more successful than 1.0 °C and 6.3 °C/min in preserving %IMS and %IPL. DMSO preserved %IMS, %IPL, and %IAC better than glycerol. To determine the best overall cryopreservation protocol, a sperm quality index was calculated, giving equal weight to each of the three indicators of cryosurvival. Because there were significant interactions between freeze rate and cryoprotectant concentration, each treatment was compared with all others. The sperm quality index analysis revealed that tegu sperm frozen at 0.3 °C/min with 12% DMSO exhibited the highest postthaw viability compared with all other treatments.

Identification of ultrastructural and functional damages in sperm from six-banded armadillos (Euphractus sexcinctus) due to cryopreservation

Abstract: The aim of the study was to cryopreserve the semen of six-banded armadillos (Euphractus sexcinctus) in Tris-yolk and glycerol diluent, and to determine the damage caused by the freezing-thawing process, using fluorescent markers and ultrastructural analysis. Semen samples (n=11) collected from 4 adult six-banded armadillos by electroejaculation were cryopreserved in Tris diluent plus 20% egg yolk and 3% glycerol, in a fast freezing curve. Classical analysis of samples was performed after dilution, refrigeration and thawing, followed by fluorescence analysis, using a combination of fluorescent probes to assess membrane integrity (propidium iodide - PI and Hoechst - H342), and mitochondrial activity (CMXRos - Mito Tracker Red®). We also used the ultrastructural analysis to verify possible morphological alterations caused by cryoinjuries. When compared with fresh samples, we verified a significant decline in all the armadillos' semen parameters after thawing, in which only 6.1% motile sperm were found. However, the percentage of sperm which remained with viable (13%) and functional (24.7%) membranes after thawing suggests that some cells could be live but immotile. Analysis using fluorescent markers revealed that the mitochondria of armadillos' sperm is highly sensible to the freezing protocol and the findings through ultrastructure analysis proved this statement. Additionally, the images obtained by transmission electron microscopy revealed that frozen-thawed sperm presented damaged plasma membrane, nuclear modifications as changes in chromatin and acrossomal changes relative to sperm capacitation. In conclusion, this study is the first attempt to cryopreserve the semen of an armadillo species, and to help us to identify critical points on the freezing-thawing procedure in order to improve the protocol.

Boar Differences In Artificial Insemination Outcomes: Can They Be Minimized?

In Western countries, where pig breeding and production are intensive, there is a documented variability in fertility between farms with boar-related parameters only accounting to 6% of this total variation of in vivo fertility. Such low boar effect could be a result of the rigorous control of sires and ejaculates yielding AI-doses exerted by the highly specialized AI-centres that monopolize the market. However, some subfertile boars pass through these rigorous controls and consequently reach the AI-programmes. Here, we discuss why testing young boars for chromosomal defects, sperm nuclear chromatin integrity and in vitro fertilizing ability can be discriminative and economically sound for removing these less fertile boars. Alongside, we discuss why boars differ in the ability of their sperm to tolerate cryopreservation or sex sorting.

The Fertility of Frozen Boar Sperm When used for Artificial Insemination

One of the limits to practical use of frozen boar sperm involves the lowered fertility when used for artificial insemination. Years of studies have shown that 5-6 billion sperm (approximately 3 billion viable) used in single or multiple inseminations results in pregnancy rates most often between 60 and 70% and with litter sizes between nine and 10 pigs. Yet today, it is not uncommon for studies to report pregnancy rates from 70 to 85% and litter sizes with 11-12 pigs. While global statements about the incidence and reasons for higher fertility are not conclusive, incremental fertility improvements appear independently associated with use of a minimum number of viable sperm (1-2 billion), insemination timing that increases the probability that sperm will be present close to ovulation for groups of females, selection for boar sperm survival following cryopreservation, and modification of the freeze and thaw conditions using additives to protect sperm from oxidative damage. Studies show that techniques such as intrauterine and deep uterine insemination can provide an opportunity to reduce sperm numbers and that control of time of ovulation in groups of females can reduce the need for multiple inseminations and improve the chance for AI close to ovulation. However, optimal and consistent fertility with cryopreserved boar sperm may require a multifaceted approach that includes boar selection and screening, strategic use of additives during the freezing and thawing process, post-thaw evaluation of sperm and adjustments in sperm numbers for AI, assessment of female fertility and ovulation induction for single insemination. These sequenced procedures should be developed and incorporated into a quality control system for improved fertility when using minimal numbers of cryopreserved boar sperm.

Methods for Improving In Vitro and In Vivo Boar Sperm Fertility

Fertility of boar spermatozoa is changed after ejaculation in vivo and in vitro. During processing for in vitro fertilization (IVF), although spermatozoa are induced capacitation, resulting in a high penetration rate, persistent obstacle of polyspermic penetration is still observed with a high incidence. For artificial insemination (AI), we still need a large number of spermatozoa and lose a majority of those in the female reproductive tract. Fertility of cryopreserved boar spermatozoa is still injured through freezing and thawing process. In the present brief review, factors affecting fertility of boar sperm during IVF, AI and cryopreservation are discussed in the context of discovering methodologies to improve it.

Effects of storage in different semen extenders on the pre-freezing and post-thawing quality of boar spermatozoa

The aim of this study was to investigate the effects of storage of semen in different commercial extenders on the pre-freezing and post-thawing quality of boar spermatozoa. Semen was diluted in BTS, Androhep (AH) and Gedil (GD), stored for 24 h at 17°C, and then frozen in accordance with the cryopreservation protocol. Analyses of the quality of spermatozoa included: motility, normal apical ridge (NAR) acrosome, plasma membrane integrity (PMI), mitochondrial membrane potential (MMP), measurements of ATP content and activity of superoxidase dismutase (SOD) and glutathione peroxidase (GPx). Prior to the freezing process, no significant effect of the extender on the sperm quality parameters was noted. After thawing the spermatozoa it was demonstrated that the type of extender used influenced PMI, MMP, ATP content and activity of GPx. In the AH extender the percentage of spermatozoa with PMI and ATP content in spermatozoa was significantly higher (P<0.05) as compared to the BTS or GD extenders. In addition, semen stored in the AH was characterised by a statistically higher (P<0.05) percentage of spermatozoa with MMP and increased activity of GPx as compared with the BTS. The results obtained indicate that for the cryopreservation process, boar spermatozoa stored for 24 hours in liquid state can be used. However, the type of extender used prior to freezing may have a significant effect on the post-thawing quality of the spermatozoa. The AH extender better secured the quality of thawed boar spermatozoa as compared with the BTS or GD.

Will AI in pigs become more efficient?

AI is commercially applied worldwide to breed pigs, yielding fertility outcomes similar to those of natural mating. However, it is not fully efficient, as only liquid-stored semen is used, with a single boar inseminating about 2000 sows yearly. The use of liquid semen, moreover, constrains international trade and slows genetic improvement. Research efforts, reviewed hereby, are underway to reverse this inefficient scenario. Special attention is paid to studies intended to decrease the number of sperm used per pregnant sow, facilitating the practical use of sexed frozen-thawed semen in swine commercial insemination programs.

Cryopreservation of Piau-Breed Wild Boar Sperm: Assessment of Cooling Curves and Centrifugation Regimes

This study aimed to assess the effects of different cooling curves and centrifugation regimes used in cryopreservation protocols on the post-thaw viability of Piau-breed wild boar (Sus scrofa) sperm using in vitro assessment tests. Two centrifugations (800 g for 10 min and 2400 g for 3 min) and two cooling curves (conventional cooling using nitrogen vapour - freezing 1 and automated cooling using a programmed freezing machine - freezing 2) were tested. Therefore, the treatments were divided into M3 - centrifugation at 2400 g for 3 min and freezing 2; M10 - centrifugation at 800 g for 10 min and freezing 2; R3 - centrifugation at 2400 g for 3 min and freezing 1; and R10 - centrifugation at 800 g for 10 min and freezing 1. No significant differences (p > 0.05) between treatments occurred post-thawing regarding the total sperm motility means recorded. The mean values of the different treatments were not different from each other regarding the supravital staining (SV), hypo-osmotic test (HO), sperm-egg binding assay or sperm morphology. This study showed that both the cooling curve and the centrifugation regime affected the quality of post-thaw sperm, and centrifugation for shorter times and cooling curves using automated cooling are the most suitable for minimizing sperm injury.