A short hypoosmotic swelling test for the prediction of boar sperm fertility

Male reproductive biotechnologies in South American Camelids Part I: Semen collection, evaluation and handling

This review describes the first steps necessary to apply any reproductive biotechnology in South American camelids (SAC) semen or sperm: sample collection, evaluation and handling. In camelids, the length and position adopted for mating and the site of semen deposition have conditioned semen collection methods. The advantages and disadvantages of available collection methods are summarized. The two main drawbacks for applying assisted reproductive techniques in SAC: sperm concentration and rheological characteristics are discussed. Techniques currently available to reliably evaluate diverse sperm characteristics are described, as are different methods to improve semen handling. Finally, advances made regarding the role of seminal plasma in SAC spermatozoon physiology are addressed. Part II of the review will cover the subsequent steps of dilution and cryopreservation of samples. Current results obtained using artificial insemination (AI) in SAC will also be covered in Part II.

Spermiogram, Kinetics, Flow Cytometric Characteristics and DNA Damage Degree in Boar Ejaculates: Summarization and Clustering

Boar semen analysis includes sperm motility, concentration, morphology and other more complex analyses such as membrane integrity, DNA damage and seminal plasma components. This study aims to summarize these numerous data by linear combinations of them, to classify ejaculates in several categories (clusters) and to investigate the potential differences among clusters on fertility and prolificacy. Young Pietrain boars (23 ± 3.6 months) were investigated: ten boars from the Nucléus genetic line (group 1: 90 ejaculates weekly) and five boars from the Batallé genetic line (group 2: 30 ejaculates weekly). Computer-assisted semen analysis (CASA) examined motility. Sperm viability, acrosome reaction, early apoptosis, mitochondrial activity and DNA damage were studied by flow cytometry analysis. SPSS v.26 software was used to perform principal component analysis (PCA) and clustering. Three principal components (PC1: speed; PC2: linear path; PC3: DNA damage) were detected and four clusters identified in both groups. Clusters also differed significantly in several variables not included in these PCs (group 1: beat cross frequency and poly (ADP-ribose) polymerase; group 2: cathepsin B, abnormal forms, mitochondrial activity and high DNA stainability). PCA and clustering achieved adequate description of these ejaculates, but no differences among clusters were found for fertility or prolificacy, probably because the minimum sperm requirements had been met.

Effect of tyrode albumin lactate pyruvate and modified Krebs Ringers broth media on in vitro capacitation of HD-K75 boar spermatozoa at different period of incubation

In vitro capacitation allows for a greater understanding of the mechanisms underlying fertilization and the development of improved reproductive techniques for improving fertility rates in porcine. Tyrodes albumin lactate pyruvate (TALP) and modified Krebs Ringers Broth (m-KRB) are two medias that are commonly used in research experiments to induce capacitation in boar spermatozoa (Cañón-Beltrán et al., Theriogenology, 198, 2023 and 231; Oberlender et al., Archivos de Medicina Veterinaria, 44, 2012 and 201; Sahoo et al., International Journal of Biological Macromolecules, 241, 2023 and 124502). Moreover, understanding the morphological and functional changes in boar spermatozoa at different hours of capacitation periods might aid in the development of novel techniques for improving sperm quality and increasing the litter size. This study was carried out to investigate the effect of Tyrode albumin lactate pyruvate and modified Krebs Ringers Broth media on in vitro capacitation of HD-K75 boar spermatozoa at three different periods of incubation. A total of 24 ejaculate from four clinically healthy, 10-12 months aged HD-K75 boars, maintained at ICAR-All India Coordinated Research Project (AICRP) on pig were selected. Semen was collected by 'Simple fist' method using a portable dummy. The semen samples having 200 mL volume, 103 × 106 spermatozoa/ml concentration and 70% initial motility were selected and split into two parts and suspended in TALP and m-KRB media, respectively, and incubated for 5 h at 37°C. Seminal parameters viz. sperm viability, plasma membrane integrity and acrosomal integrity were estimated in the samples at 0, 3 and 5 h of incubation. This study revealed that there was significant variation between media in live acrosome-reacted (p < .05) and HOST-reacted (p < .01) spermatozoa, while between capacitation periods significant (p < .01) variation was observed in hyperactivated spermatozoa, live acrosome-reacted spermatozoa, HOST-reacted spermatozoa, FITC-labelled PSA, extracellular protein and sperm cholesterol. Non-significant variation was observed in total phospholipid. TALP showed overall better consequence on sperm viability, plasma membrane and acrosomal integrity of boar spermatozoa. From this study, it could be concluded that both TALP and m-KRB media were virtuous to induce capacitation in HD-K75 boar spermatozoa. TALP media, however, had a better effect on sperm viability, plasma membrane and acrosomal integrity of boar spermatozoa. Out of the three different periods, 3 h capacitation period resulted in significantly (p < .01) higher incidence of sperm viability, plasma membrane and acrosomal integrity in HD-K75 boar spermatozoa.

Clustering of spermatozoa examined through flow cytometry provides more information than the conventional assessment: a resilience to osmotic stress example

Context Conventional sperm quality tests may not be sufficient to predict the fertilising ability of a given ejaculate; thus, rapid, reliable and sensitive tests are necessary to measure sperm function. Aims This study sought to address whether a cluster analysis approach based on flow cytometry variables could provide more information about sperm function. Methods Spermatozoa were exposed to either isotonic (300mOsm/kg) or hypotonic (180mOsm/kg) media for 5 and 20min, and were then stained with SYBR14 and propidium iodide (PI). Based on flow cytometry dot plots, spermatozoa were classified as either viable (SYBR14+ /PI- ) or with different degrees of plasma membrane alteration (SYBR14+ /PI+ and SYBR14- /PI+ ). Moreover, individual values of electronic volume (EV), side scattering (SS), green (FL1) and red (FL3) fluorescence were recorded and used to classify sperm cells through cluster analysis. Two strategies of this approach were run. The first one was based on EV and the FL3/FL1 quotient, and the second was based on EV, SS and the FL3/FL1 quotient. Key results The two strategies led to the identification of more than three sperm populations. In the first strategy, EV did not differ between membrane-intact and membrane-damaged sperm, but it was significantly (P P P Conclusions Cluster analysis based on flow cytometry variables provides more information about sperm function than conventional assessment does. Implications Combining flow cytometry with cluster analysis is a more robust approach for sperm evaluation.

Myo-inositol improves the viability of boar sperm during liquid storage

Introduction

Liquid preservation of boar semen is a highly preferred method for semen preservation in pig production. However, oxidative stress is the main challenge during the liquid preservation of boar semen in a time dependent manner. Therefore, supplementation of sperm with antioxidants during storage to protect them from oxidative stress has been the focus of recent research. Myo-inositol (Myo-Ins), the most active form of inositol, which belongs to the vitamin (Vit.) (B1 group has been shown to improve semen quality) (1). This study aimed to investigate whether Myo-Ins supplementation protects boar sperm in liquid preservation against oxidative stress and determine the appropriate concentration of Myo-Ins to be used in this regard.

Methods

Boar sperm was diluted with a semen extender with different concentrations of Myo-Ins (2, 4, 6, and 8 mg/mL) depending on the previous studies (1, 24). Sperm motility and viability, plasma membrane and acrosome integrity, mitochondrial membrane potential (MMP), semen time survival, and gene expression were measured and analyzed on days 0, 1, 3, 5, and 7 for the different samples.

Results

Different concentrations of Myo-Ins exerted different protective effects on the boar sperm quality. The addition of 2 mg/mL Myo-Ins resulted in higher sperm motility and viability, plasma membrane and acrosome integrity, MMP, and effective survival time. Investigation of mRNA expression patterns via qRT-PCR suggested that the 2 mg/mL Myo-Ins sample had increased expression of antioxidative genes.

Conclusion

The addition of Myo-Ins to semen extender improved the boar semen quality by decreasing the effects of oxidative stress during liquid preservation at 17°C. Additionally, 2 mg/mL is the optimum inclusion concentration of Myo-Ins for semen preservation.

Photoperiod and Melatonin Supplementation: Variable Effects on the Quality of Chilled Dog Semen

The addition of melatonin in seminal extenders due to its antioxidant properties and its beneficial role in sperm preservation has been previously described, especially in seasonal species. The aim of this study was to study a potential seasonal effect based on photoperiod duration when adding a physiological concentration of melatonin in the canine ejaculate. A total of 24 ejaculates were obtained from 10 healthy dogs during the increasing photoperiod (from December 21 to June 21), whereas 12 ejaculates were collected from five healthy individuals during the decreasing photoperiod (from June 22 to December 20). Each ejaculate was separated into two aliquots, and one of them remained as a control, whereas melatonin (100 pM) was added to the other one (C and M treatment groups, respectively). Diluted semen was refrigerated at 5°C. On days 0, 1, 2, 3, and 6, sperm motility analyses were performed using a CASA system and hypoosmotic swelling test (HOST), osmotic resistance test (ORT), and flow cytometry analysis. No effect of melatonin on motility was detected in either photoperiod. Negative effects of melatonin were found for acrosomal defects, apoptosis, and viability in the decreasing photoperiod. The addition of melatonin to sperm in the decreasing photoperiod could create such a high level that it would cause the described negative effects. We found a beneficial effect of melatonin in the increasing photoperiod on acrosomal defects and apoptosis during 0–6 days. Melatonin treatment also increased viability in the short term (days 1 and 2) for both photoperiods. Also, melatonin can provide certain beneficial effects on mitochondrial activity in the medium term (days 2 and 3) in the decreasing photoperiod.

Serum Insulin-like Growth Factor-1 Is a Biomarker of Testosterone Production and Intact Acrosome in Asian Elephants (Elephas maximus)

Simple Summary

In Thailand, the low fertility rate of Asian elephants has been identified. Factors contributing to poor semen quality in the elephants are not fully understood. Insulin-like growth factor-1 (IGF-1) is related to male infertility. It plays an essential role in testicular development by stimulating cell proliferation, differentiation, and steroidogenesis. In addition, there is increasing evidence that IGF-1 plays a critical role in spermatogenesis. This may be conducive to finding the causes of poor sperm quality in Asian elephants (Elephas maximus). In the present study, we investigated the relationships among serum IGF-1, serum testosterone level, and semen parameters in seven elephant bulls. The findings suggest that serum IGF-1 concentration is likely to predict sperm quality like acrosome integrity. The further mechanism by which IGF-1 affects sperm quality requires further investigation.

Abstract

The objective of this study was to find relationships among serum IGF-1, serum testosterone, seminal plasma IGF-1 concentrations and semen parameters in Asian elephants (Elephas maximus). A total of 17 ejaculates (one to three ejaculates/bull) were collected from seven captive elephant bulls by performing rectal massage. Before each ejaculation, blood samples were obtained for serum IGF-1 and testosterone assays. Subsequently, the semen characteristics of each ejaculate were evaluated. Mean serum IGF-1 concentration of elephant bulls was estimated as 326.3 ± 114.6 ng/mL (median, 286.2 ng/mL; range, 167.4–542.7 ng/mL). An increase in serum IGF-1 concentration was found to correlate with the percentage of spermatozoa with intact acrosomes. In addition, IGF-1 concentration was positively correlated with testosterone level. However, seminal IGF-1 concentrations could not be detected. In conclusion, our findings suggest that serum IGF-1 concentration is likely a biomarker of normal testicular functions, particularly spermatogenesis in elephants. Moreover, this commercial IGF-1 ELISA is eligible for analyzing serum IGF-1 concentration in Asian elephants.

Hypo-Osmotic Swelling Test (HOST) for Feline Spermatozoa: The Simplified Procedure and the Aspect of Sperm Morphology

Hypo-osmotic swelling test (HOST) is used to assess the functional integrity of sperm plasma membranes in many species. The primary aim of this study was to test a simplified HOST procedure for the evaluation of feline semen. The second objective was to check if sperm abnormalities can influence the results of this test. Urethral semen was collected from 19 male, domestic cats. In Exp. 1, HOST was performed in different media (50 mOsm/kg fructose or distilled water), temperature (37 °C or room temperature) and time (5 and 30 min). In Exp. 2, the potential effect of sperm abnormalities on HOST results was assessed by observing individual normal and abnormal spermatozoa microinjected into droplets of distilled water. The results showed no differences between the HOST results performed in different media, temperature and time. Viable abnormal spermatozoa were able to swell under hypo-osmotic conditions in the same manner as normal ones, except spermatozoa with distal droplets, which showed a higher frequency of ‘despiralization’. In conclusion, HOST can be reliably performed at 0 mOsm/kg for 5 min at room temperature, which may contribute to a wider use of this test under clinical environments. Viable abnormal spermatozoa are able to swell under hypo-osmotic conditions; therefore, their presence in the ejaculate would not bias the results of HOST when total coiling is calculated.

Microenvironment of the male and female reproductive tracts regulate sperm fertility: Impact of viscosity, pH, and osmolality

BACKGROUND

Terminally differentiated mammalian sperm are exposed to gradients of viscosity, pH, and osmolality both in the male and female reproductive tract during their perilous journey to quest the ovum. The complex physicochemical factors play an integral role in preparing sperm for the fertilization process.

OBJECTIVES

To elucidate the influence of the reproductive tract microenvironment especially viscosity, pH, and osmolality in regulating sperm functional and fertilization competence.

MATERIALS AND METHODS

The data used in this review were collected from the research papers and online databases focusing on the influence of viscosity, pH, and osmolality on sperm function.

DISCUSSION

The gradients of viscosity, pH, and osmolality exist across various segments of the male and female reproductive tract. The changes in the viscosity create a physical barrier, pH aid in capacitation and hyperactivation, and the osmotic stress selects a progressive sperm subpopulation for accomplishing fertilization. The sperm function tests are developed based on the concept that the male genotype is the major contributor to the reproductive outcome. However, recent studies demonstrate the significance of sperm genotype-environment interactions that are essentially contributing to reproductive success. Hence, it is imperative to assess the impact of physicochemical stresses and the adaptive ability of the terminally differentiated sperm, which in turn would improve the outcome of the assisted reproductive technologies and male fertility assessment.

CONCLUSION

Elucidating the influence of the reproductive tract microenvironment on sperm function provides newer insights into the procedures that need to be adopted for selecting fertile males for breeding, and ejaculates for the assisted reproductive technologies.

Semen analysis of boars under intertropical conditions reveals the relevance of proximal and distal cytoplasm droplets for sperm functional integrity

This work aimed to establish whether the temperature humidity index (THI) under different intertropical zones affects the retention of cytoplasmic droplets (CDs), sperm function and DNA integrity in boars. With this purpose, two separate studies were devised. In the first one, 49 boars from six farms were collected every 45 days (230 ejaculates). THI were measured daily, and sperm parameters were evaluated. Boars were classified into three groups based on the incidence of ejaculates having more than 25% spermatozoa with CDs: persistent (at least three consecutive ejaculates), moderate (less than three ejaculates) and absent (no ejaculate having ≥25% spermatozoa with CDs). Farms were classified based on THI through cluster analysis into two groups. In the second study, 32 liquid-stored semen samples were classified based on three cluster analysis: low and high incidence of proximal (PCDs), distal (DCDs) CDs and a combination of PCD and DCDs. high THI farms presented significantly (p < .05) higher proportions of boars with moderate and persistent incidence of CD than those with low THI. In study 2, the presence of PCDs was negatively correlated with sperm DNA integrity (r = -0.691; p < .01). However, differences between groups were more apparent when ejaculates were classified based on both PCDs and DCDs than when PCDs or DCDs were considered separately. In conclusion, classification of boars according to the severity and persistence of CDs in boars allows understanding more clearly the dynamics of CD retention and the effects of ambient temperature and relative humidity. Additionally, the joint analysis of both PCDs and DCDs is necessary in routine sperm quality analyses.

Individual and Combined In Vitro Effects of Deoxynivalenol and Zearalenone on Boar Semen

Mycotoxins deoxynivalenol (DON) and zearalenone (ZEN) can negatively affect pig health. However, little is known about their effects on boar semen. We assessed the individual and combined effects of DON and ZEN on boar semen in vitro. In a pretrial, we determined the minimum dose (MiD) of each mycotoxin that induces a significant alteration of sperm progressive motility, as investigated using computer-assisted semen analysis (CASA). In the main trial, the individual and combined effects of each mycotoxin’s MiD on sperm motility and kinetics (CASA analysis), morphology (SpermBlue staining), viability (calcein-propidium iodide staining), membrane functional status (hypoosmotic swelling test), and chromatin integrity (acridine orange staining) were analyzed. Pretrial results suggested a MiD of 50.6 μM and 62.8 μM for DON and ZEN, respectively. In the main trial, DON and ZEN administered at MiD significantly affected CASA parameters (e.g., increase of immotile spermatozoa, reduction of progressive motile spermatozoa), decreased sperm viability, and affected sperm morphology (head abnormalities) and membrane functional status. DON and ZEN showed less than additive effects on most parameters tested and a synergistic effect on viability and on two CASA parameters. In conclusion, DON and ZEN showed individual and combined toxic effects on boar semen in vitro.

Insemination of sows with seminal doses prepared by a two-step hypothermic dilution does not impair the reproductive performance at farm

Reproduction in swine is mostly carried out through artificial insemination (AI). For this purpose, AI studs collect the ejaculates, analyse the sperm quality, dilute and package to produce seminal doses and ship them to sow farms to carry out the AI. Temperature is controlled during the process to avoid sperm damage. Semen is diluted in the extender in a one-step or a two-step process where the second can be isothermic (approximately 32°C) or hypothermic (room temperature 21-22°C). Both techniques are currently performed, and the latter could reduce time and costs, but the literature available comparing the processes is scarce and presents discrepancies. To date, there are no studies about its impact in fertility. This study compared hypothermic two-step dilution (HTSD) and isothermic two-step dilution (ITSD) in laboratory and field trial to elucidate whether HTSD has any effect. Ejaculates from 72 boars in nine AI studs were split and processed with both techniques using a high-performance extender and evaluated in laboratory. Four farms inseminated 345 sows with samples of four of these AI studs, and their fertility and prolificacy were registered. Results show no significant differences between doses prepared by HTSD and ITSD technique, having no impact in laboratory results (percentage of motile sperm, short hypoosmotic swelling test (sHOST) and short osmotic resistance test (sORT), viable sperm, damaged acrosomes, sperm under early apoptosis, high mitochondrial membrane potential (p > .1), fertility (92.2% versus 94.1%, p = .45) or farrowing rate (15.8 ± 0.3 versus 16.1 ± 0.3 p = .46). In conclusion, our results suggest that HTSD of semen on extender could be safely implemented in AI studs under the conditions tested.

The effect of astaxanthin supplementation on the post-thaw quality of dog semen

Astaxanthin is a member of the carotenoid family well known for its anti-cancer, anti-diabetic, anti-inflammatory and antioxidant nature. This study was designed to investigate the effects of astaxanthin supplementation of the extender (buffer 2) on post-thaw dog semen quality. Semen from four healthy dogs was collected by digital manipulation twice a week. The ejaculates were pooled, washed, divided into four equal aliquots, diluted with the extender supplemented with different concentrations of astaxanthin (0, 0.5, 1 and 2 µM) and cryopreserved. The results showed that 1 µM astaxanthin was the optimum concentration that led to significantly higher (p < .05) post-thaw motility, kinematic parameters and viability than the other groups. In comparison with the control group, sperm samples supplemented with 1 µM astaxanthin showed significantly higher (p < .05) sperm counts with intact membranes (55.7 ± 0.6% vs. 51.3 ± 0.9%), intact acrosome (58.4 ± 0.7% vs. 53.5 ± 0.6%), active mitochondria (54.9 ± 0.5% vs. 42.6 ± 0.6%) and normal chromatin (67.6 ± 0.9% vs. 61.7 ± 0.6%). Furthermore, astaxanthin-supplemented samples showed significantly lower expression levels (p < .05) of pro-apoptotic (BAX), oxidative induced DNA damage repair (OGG1), oxidative stress-related (ROMO1) genes and higher expression levels of anti-apoptotic (BCL2), and sperm acrosome-associated (SPACA3) genes compared to the control. Thus, supplementation of 1 µM astaxanthin in semen extender results in improved freeze-thaw sperm quality of the dog.

Influence of nonylphenol from multilayer plastic films on artificial insemination of sows

Artificial insemination is common practice in mass livestock farming. Recently, it was shown that chemicals leaching from multilayer plastic bags affect the fertility of boars, although common quality tests did not show any impact on the sperm. It is not clear whether this incidence was a single case or whether it could be a systematic problem. Therefore, we studied six multilayer plastic bags. A total of 49 compounds were found, but most of them were at very low intensity. Nonylphenols in the range of 19-99 μg/g plastic were found. Migration tests using water and 10% ethanol as simulants, to mimic the behavior of semen with the extender, were performed. The most interesting migrants in terms of potential reprotoxicity were identified as nonylphenols. The identification in depth demonstrated the presence of 10 isomers of nonylphenol with a total concentration range between 16 to 58 μg/Kg simulant, among other migrants at lower concentration. The influence of these nonylphenols and their maximum tolerable concentration in direct contact with semen from boars was studied. Motility, viability, mitochondrial activity and acrosomes reacted were significantly affected at 10 mg/Kg of nonylphenols in contact with the sperm, but in vitro penetration rate was significantly decreased with only 2 mg/Kg. Insight into the mode of action is also provided.

Long-term storage of boar seminal doses contaminated with Proteus vulgaris: A dose-dependent effect on sperm motility and sperm-bacteria interaction

This study evaluated how Proteus vulgaris affects sperm quality and sperm-bacteria interaction in stored semen samples. A strain of P. vulgaris resistant to streptomycin, penicillin, lincomycin and spectinomycin was added to boar semen in doses of 10³, 10⁵, 10⁶, 10⁷ and 10⁸ CFU/mL. A sample in which there was no addition of P. vulgaris was the negative control. Sperm quality was determined by evaluating sperm motility and morphology using the computer-assisted sperm analysis (CASA) system, and plasma membrane and acrosome integrity using flow cytometry at 0, 1, 2, 4, 6, 8 and 10 days of liquid-storage at 17 °C. At the same time points, pH, sperm agglutination, sperm-bacteria interaction and bacterial growth were also assessed. There was impaired sperm motility when the infective doses of P. vulgaris were equal to or greater than 10⁵ CFU/mL with the effect being dose-dependent (P < 0.05). When infective doses of P. vulgaris were of 10⁶ to 10⁸ CFU/mL there were impairments of plasma membrane and acrosome integrity by Day 1 of storage (P < 0.05), and alkalinisation of the storing medium by Day 4 (P < 0.05). Bacterial adhesion increased when infective dose of P. vulgaris was greater and as duration of storage increased. P. vulgaris had a high affinity for the mid- and principal pieces of sperm cells. It is concluded there were alterations in sperm motility in samples infected with P. vulgaris that were associated with bacterial adhesion and medium alkalinisation.

Rest days and storage of boar semen at 17°C: Effect on motility and sperm concentration

Boar fertility is an important factor in farm production; it is therefore of interest to determine factors which reduce the fertilising capacity of semen samples stored at 17°C for use in intrauterine insemination. This work evaluated the effect of the number of rest days between each mounting of the boar, and the number of days that the semen was stored at 17°C, on sperm motility and semen concentration. We also analysed whether the boar's age influenced the sperm concentration. The results showed that only the total motility diminished as the storage time at 17°C increased (p < .05). A low negative correlation was observed between the variables' rest days and total and progressive motility. The sperm concentration presented no relation with rest days or the boar's age. The boars' rest days had no effect on motility and sperm concentration in the males studied, allowing them to be used with the frequencies described with no effect on these parameters.

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.

Análise da integridade funcional dos espermatozoides de Tayassu pecari por diferentes soluções hiposmóticas e osmolaridades

RESUMO Queixada (Tayassu pecari) é um mamífero neotropical, classificado como vulnerável devido à caça e à destruição de seu habitat. Em razão das dificuldades na reprodução em cativeiro, técnicas de reprodução assistida podem ser aplicadas em programas de repovoamento da espécie. Dessa forma, objetivou-se identificar o melhor protocolo de teste hiposmótico (HOST) para avaliar a integridade funcional dos espermatozoides de queixada. O sêmen de quatro machos adultos foi coletado com auxílio de eletroejaculador após contenção física e protocolo de sedação e anestesia. O sêmen foi avaliado quanto às características macro e microscópicas e diluído nas seguintes soluções hiposmóticas: água destilada (0mOsmol/L), sacarose (50, 100, 150mOsm/L) e frutose (50, 100, 150mOsm/L). Cada amostra foi incubada em duplicata, e uma sofreu fixação em solução de citrato de sódio formolizado a 4%. Duzentos espermatozoides foram avaliados por amostra e classificados em reativos ou não ao HOST. Todas as soluções testadas foram semelhantes em identificar o percentual de espermatozoides reativos, independentemente de a amostra ser ou não fixada (P>0,05). Dessa forma, pode-se usar água destilada como HOST por este apresentar resultados similares e por ser um teste mais barato.

Effect of nicotinic acid on the plasma membrane function and polyunsaturated fatty acids composition during cryopreservation in boar sperm

This study was conducted to evaluate the effect of nicotinic acid on plasma membrane integrity and fatty acid composition in frozen-thawed boar sperm. Boar semen was cryopreserved using freezing extender containing nicotinic acid (NA), then plasma membrane integrity, osmotic equilibration, lipid peroxidation and fatty acid were analysed. The plasma membrane integrity of frozen-thawed sperm was significantly higher in the 10 mM NA than in the 0 and 20 mM NA treatment groups (p < 0.05). Additionally, the osmotic equilibration ability was not different in treatment groups, but lipid peroxidation was significantly decreased in the 10 mM NA treatment group (p < 0.05). The saturated fatty acids were significantly decreased in the 10 mM NA treatment group, and C18:1n-9, C18:2n-6, C20:4n-6, C22:5n-6 and C22:6n-3, and total polyunsaturated fatty acids (PUFAs) were significantly increased in the 10 mM NA treatment groups (p < 0.05). In summary, 10 mM NA improved plasma membrane integrity, inhibited lipid peroxidation and increased PUFAs in frozen-thawed boar sperm. These results suggest that NA may be useful to protect the plasma membrane and inhibit the loss of PUFAs for sperm cryopreservation in pigs.

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.

A comparative study of the effects of Escherichia coli and Clostridium perfringens upon boar semen preserved in liquid storage

The present study compares the sperm quality of boar seminal doses artificially inoculated with Escherichia coli and Clostridium perfringens, and maintained in liquid storage at 15°C for a 9-day period. Seminal doses from 10 sexually mature Piétrain boars were diluted in a Beltsville Thawing Solution (BTS)-based extender and infected either with E. coli or C. perfringens, with bacterial loads ranging from 10¹ to 10⁷cfumL^-1. During storage, the changes in sperm quality were determined by assessing pH, sperm viability, sperm motiliy, sperm morphology, sperm agglutination degree, and sperm-bacteria interaction. The infection of seminal doses led to an alkalinization of the medium, which was of higher extend in doses infected with C. perfringens. The effect of contamination on sperm viability and motility relied on bacterial type and load. Therefore, while E. coli was more harmful than C. perfringens in bacterial loads ranging from 10¹ to 10⁶cfumL^-1, the detrimental impact of C. perfringens was more apparent than that of E. coli at a bacterial load of 10⁷cfumL^-1. Despite sperm morphology not being affected by either bacterial type or load, sperm agglutination and sperm-bacteria interaction were characteristic of doses infected with E. coli, and increased concomintantly with bacterial load and along storage period. In conclusion, the effects of infection by E. coli on sperm quality were dependent of both bacterial load and storage period, whereas the effects of C. perfringens were mainly dependent on the bacterial load, with a threshold at 10⁷cfumL^-1 from which the sperm quality of seminal doses was greatly impaired.

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.

Determination of appropriate cryopreservation protocols for epididymal cat spermatozoa

Effects of Equex and glycerol additions and sample dilution step on frozen-thawed epididymal cat spermatozoa were investigated. The epididymal sperm pellets were resuspended in extenders using one- (groups III and IV) or two- (groups I, II, V and VI) step dilution. For one-step dilution, the pellets were resuspended in plain egg yolk-Tris medium (EYT) + 5% glycerol with (IV)/without (III) 0.5% Equex and cooled (4(°) C, 1 h). For two-step dilution, the pellets were resuspended in EYT (I and V) and in EYT + 3% glycerol (II and VI), cooled and further diluted with EYT + 10% glycerol with (I)/without (V) 1% Equex and with EYT + 7% glycerol with (II)/without (VI) 1% Equex. Immediately after freeze-thawing, no differences (p > 0.05) were found in the motility, viability and membrane integrity (HOST) among the groups except the lowest HOST in IV (p = 0.005 to p = 0.04). The acrosome integrity (FITC) in group I was comparable to that in group II (p > 0.05) and was higher than the rest (p < 0.001 to p = 0.02). At 2 h after thawing, the motility, viability and HOST were comparable among the groups (p > 0.05) except the lower percentages of viability in III (p = 0.008 to p = 0.3) and of HOST in IV (p = 0.005 to p = 0.2). Two-step dilutions with Equex (I, II) were more beneficial for the FITC at 2 h than without Equex (V) (p = 0.005 and p = 0.02) and than one-step dilutions (III, IV) (p < 0.001 to p = 0.02). In conclusion, epididymal cat sperm quality after freeze-thawing could be improved when Equex was added and two-step dilution was performed during freezing. The extenders prepared for the first step of dilution could be with (3%) or without (0%) glycerol.

Modified hypoosmotic swelling test for the assessment of boar and bull sperm sensitivity to cryopreservation

Routine methods for the evaluation of sperm quality are not sufficiently useful to determine the sensitivity of sperm cells to cold shock. The aim of our preliminary study was to determine whether the sperm plasma membrane integrity evaluated by modified hypoosmotic swelling test based on simple hypoosmotic swelling test (HOS test) and eosin-nigrosin staining could be helpful in predicting the degree of boar sperm survivability during semen cryopreservation. Ejaculates collected from 24 boars and 20 bulls were used in the experiment. Fresh ejaculates were evaluated by routine sperm analysis and a modified HOS test, and subsequently frozen. Sperm cryosurvivability was defined as the percentage of motile spermatozoa that survived the freezing process. A higher percentage of sperm was recovered after the thawing of semen with a higher percentage of HOS-positive and eosin-negative sperm (P < 0.01). Both indicators were found to be correlated (r = 0.707 and r = 0.705, respectively; P < 0.01). Moreover, the percentage of HOS-positive and eosin-negative sperm was similar to the percentage of viable sperm after thawing as determined by traditional eosin-nigrosin staining in boars (50.90 ± 9.88% and 49.31 ± 11.63%, respectively) and bulls (55.91 ± 10.34% and 55.63 ± 6.64%, respectively) and both indicators showed a positive correlation (r = 0.558 and r = 0.504, respectively; P < 0.05). In conclusion, based on the obtained results, we can assume that the modified HOS test can detect differences in sperm membrane resistance which allows assessment of semen quality from the perspective of its further use, e.g. cryopreservation.

Effects of Enterobacter cloacae on boar sperm quality during liquid storage at 17°C

Contamination of fresh and extended boar sperm often occurs in farms and artificial insemination (AI) centres during semen collection, processing and storage. The presence of bacteria produces detrimental effects on boar sperm quality, which may cause economic losses in reproductive centres. The present study has evaluated for the first time how the presence of Enterobacter cloacae affects the preservation of boar spermatozoa in liquid storage at 15-17 °C for an 11-day period. With this purpose, extended semen samples from seven healthy post-pubertal boars were artificially contaminated with different sperm:bacterium ratios (2:1; 1:1; 1:5 and 1:10) of E. cloacae. The 1:0 ratio (non-inoculated) served as a negative control. The most infective ratios (i.e. 1:5 and 1:10) significantly damaged sperm motility and membrane integrity, increased sperm agglutination, and decreased the osmotic resistance of spermatozoa. In contrast, the negative impact that the lowest bacterial concentration (2:1) had on boar sperm quality was clearly lower. In addition, other parameters such as pH were also more affected at the highest infective ratios (i.e. 1:5 and 1:10), despite no damage being observed on sperm morphology. In conclusion, the present work shows that damage inflicted by the presence of E. cloacae in boar sperm during liquid storage at 15-17 °C compromises the longevity and fertilising ability of seminal doses when bacterial concentration is higher than a 1:1 ratio. Further research is warranted to address by which mechanism E. cloacae impairs boar sperm quality.

Cryopreservation of canine epididymal sperm using ACP-106c and TRIS

The objective was to cryopreserve sperm recovered from the canine epididymal cauda immediately after an orchiectomy. The sperm was stored for 12h at 4 °C using ACP-106c and TRIS as extenders. Sixty adult male dogs were used. The testis-epididymis complex (TEC) was removed, immersed in 0.9% saline and transported to the laboratory. The 60 TEC were divided into groups according to the 4 °C cooling time (0 h or 12 h) and according to the extender used for sperm recovery (ACP-106c or TRIS), forming 4 experimental groups: G0h-ACP, G12h-ACP, G0h-TRIS and G12h-TRIS. The sperm were recovered from the epididymal cauda using the retrograde flow technique. Next, 1.0 mL of ACP-106c or 1.0 mL of TRIS (preheated to 37 °C for 5 min) was added to the sperm of each epididymis. One week later, the sperm was thawed at 37 °C for 1 min, and its morphology, functionality and total and progressive sperm motilities were analyzed. Other parameters were obtained by Computer Assisted Semen Analysis (CASA). The data were submitted to multivariate analysis of variance (MANOVA) (P<0.05). The total motility values were 52.17 ± 1.78 and 49.8 ± 1.93 for groups G0h-ACP and G12h-ACP and 50.7 ± 2.06 and 43.90 ± 2.51 for groups G0h-TRIS and G12h-TRIS, respectively. A decrease in total sperm motility was observed after 12h of cooling for both extenders (P<0.05). ACP-106c can be used as an extender for freezing canine epididymal sperm, and the freezing procedure must be performed immediately after sperm recovery.

Refrigeração do epidídimo canino a 4ºC e recuperação dos espermatozoides epididimários utilizando ACP-106c

Objetivou-se avaliar a qualidade dos espermatozoides recuperados da cauda do epidídimo após a refrigeração do complexo testículo-epidídimo (CTE) de cães usando o diluidor ACP-106c. Foram utilizados 60 cães machos adultos, com peso de 10-20 kg. Após a eutanásia, removeu-se o CTE que foi imerso em solução fisiológica 0,9% e transportado em caixa térmica ao laboratório a 30ºC. Para a refrigeração e recuperação dos espermatozoides epididimários, os 60 pares do CTE foram divididos em 4 grupos, de acordo com o tempo de refrigeração do CTE e posterior recuperação espermática: G0h, G6h, G12h e G18h, em que cada par do CTE permaneceu por zero, seis, doze ou dezoito horas a 4ºC, respectivamente. A recuperação dos espermatozoides da cauda do epidídimo foi realizada pela técnica de flutuação utilizando-se o diluidor ACP-106c ou Tris. Para cada epidídimo foi adicionado 1,0 mL de um dos dois diluidores, pré-aquecidos a 37ºC por 5 minutos. Em seguida foram centrifugados a 800g/5 minutos para remoção dos resíduos celulares. Avaliou-se a morfologia, funcionalidade e motilidade espermática total e progressiva, além de parâmetros obtidos pelo CASA. Os dados foram submetidos à ANOVA seguido do teste de Turkey (P < 0,05). Em todos os parâmetros avaliados, não houve diferença entre os diluidores testados (P>0,05). Os valores de motilidade total nos grupos G0h, G6h, G12h, e G18h para o ACP-106c foram 84,4±7,7; 81,6±11,6; 88,3±6,5 e 69,5±16,9, respectivamente, e para o Tris 85,2±8,7; 77,4±14,3; 79,0±17,8 e 65,4±17,9, respectivamente. Um decréscimo na qualidade espermática foi observado após 18 horas de refrigeração em ambos os diluidores. Dessa forma pode-se concluir que o ACP-106c pode ser utilizado para recuperar os espermatozoides epididimários refrigerados e podem ser viáveis por até 12h de refrigeração.

Sperm-TALP: an alternative extender for retrieving and diluting epididymal sperm in the domestic cat

Effects of sperm-TALP (TALP) on the quality of fresh-extended and frozen-thawed epididymal cat sperm were evaluated. The epididymides suspended in Tris-glucose-citrate solution (Tris), a conventional medium, and TALP were cut into small pieces to recover epididymal sperm. In experiment 1, the sperm pellets remained after centrifugation were re-suspended (1 : 2, v/v) in Tris and TALP. The sperm quality in all four groups, that is, sperm retrieved with Tris (I and II) or TALP (III and IV) and diluted with Tris (I and III) or TALP (II and IV) was assessed. The sperm motility at the 0-h incubation in TALP-TALP was superior to that of the rest (p < 0.001 to p = 0.04). At the 2-h incubation, the motility in Tris/TALP-TALP was greater than that in Tris/TALP-Tris (p ≤ 0.001). In experiment 2, after centrifugation, the sperm pellets were added with freezing extenders and frozen. The thawed sperm previously retrieved from the epididymides with Tris and TALP were allotted so as not to further diluted (Tris/TALP-O) and to further diluted (1 : 1, v/v) with Tris (Tris/TALP-Tris) and TALP (Tris/TALP-TALP) and were evaluated the quality. At both incubation times, the motility of frozen-thawed sperm recovered with TALP (TALP-O/Tris/TALP) was comparable with or significantly higher than that in the Tris groups (Tris-O/Tris/TALP; p = 0.003 to p > 0.05). The motility and viability of thawed sperm in Tris-Tris were significantly decreased during the 2-h incubation (p = 0.007 for the motility and p = 0.01 for the viability). In both experiments, neither type of diluent (Tris vs TALP) nor incubation time (0 vs 2 h) significantly affected the sperm membrane integrity under hypo-osmotic condition (p > 0.05). According to beneficial effects on the quality of fresh-extended and frozen-thawed sperm demonstrated, sperm-TALP could be used as an alternative medium for recovering sperm from the epididymides and for diluting epididymal sperm in the domestic cat.

The osmotic tolerance of boar spermatozoa and its usefulness as sperm quality parameter

Predicting the fertility outcome of ejaculates is very important in the field of porcine reproduction. The aims of this study were to determine the effects of different osmotic treatments on boar spermatozoa and to correlate them with fertility and prolificacy, assessed as non-return rates within 60 days (NRR(60d)) of the first inseminations, and litter size (LS), respectively. Sperm samples (n=100) from one hundred healthy Piétrain boars were used to assess 48 treatments combining different osmolalities (ranged between 100 and 4000 mOsm kg(-1)), different compounds used to prepare anisotonic solutions, and two different modalities: return and non-return to isotonic conditions. Sperm quality was evaluated before and after applying the treatments on the basis of analyses of sperm viability, motility, morphology and percentages of acrosome-intact spermatozoa. Statistical analyses were performed using a one-way ANOVA and post hoc Tukey's test, linear regression analyses (Pearson correlation and multiple regression) and Jackknife cross-validation. Although three conventional parameters: sperm viability, sperm morphology and the percentages of acrosome-intact spermatozoa were significantly correlated with NRR(60d) and with LS, their respective osmotic tolerance parameters (defined for each parameter and treatment regarding with negative control) presented a higher Pearson coefficient with both fertility and prolificacy in three treatments (150 mOsm kg(-1) with non-return to isotonic conditions, 200 mOsm kg(-1) with return and 500 mOsm kg(-1) using sodium citrate and non-return to isotonic conditions). We conclude that osmotic resistance in sperm viability, sperm morphology and acrosome-intactness in the treatments mentioned above could be assessed along with classical parameters to better predict the fertilising ability of a given ejaculate.

Hyperactivated motility of frozen-thawed spermatozoa from fertile and subfertile Japanese black bulls induced by cyclic adenosine 3',5'-monophosphate analogue, cBiMPS

This study investigated whether a cyclic adenosine 3',5'-monophosphate (cAMP) analogue, cBiMPS, could induce hyperactivated motility in frozen-thawed Japanese Black bull spermatozoa and compared the ability of spermatozoa to undergo hyperactivation between fertile and subfertile bulls. Frozen-thawed spermatozoa from 3 fertile and 2 subfertile bulls were washed, suspended in BO-Hepes medium and incubated in the presence of 0.1 mM cBiMPS for up to 4 h. At 1-h intervals, the spermatozoa were examined for hyperactivated motility. The proportions of spermatozoa showing a circular swimming pattern with asymmetrical flagellar beating and those showing whiplash beating of flagella to the total number of motile spermatozoa were expressed as C% and W%, respectively. The motile spermatozoa % was barely affected by treatment with cBiMPS or the fertility status of the sperm donor, although it gradually decreased in all sperm samples during the 4-h incubation. In the fertile bulls, the C% was 0% at 0 h of incubation but rapidly increased during the 1-h incubation with cBiMPS. It then decreased slightly towards 4 h concomitantly with a gradual increase in W% towards 4 h. In the subfertile bulls, however, the cBiMPS-induced increase of C% was delayed for 1-3 h, although the incubation time-related changes in mean W% were similar between the fertile and subfertile bulls. In the vehicle controls for cBiMPS, the C% and W% were 0% throughout incubation for all the samples examined. The results suggest that hyperactivation of the flagellum can be induced by the cAMP analogue, cBiMPS, in frozen-thawed Japanese Black bull spermatozoa and that induction of hyperactivation may serve as a useful tool for detection of functional abnormality of spermatozoa from subfertile Japanese Black bulls.

The use of a hypo-osmotic swelling (HOS) test on sperm of the pig (Sus scrofa domesticus), emu (Dromaius novaehollandiae), Asian elephant (Elephas maximus), hamadryas baboon (Papio hamadryas hamadryas), and central rock rat (Zyzomys pedunculatus)

A hypo-osmotic swelling test using TALP-HEPES medium over a range of 50 to 300 mOsm/kg was applied to sperm from domestic and endangered species. Maximal responses of curling of the sperm tails were seen over a range of osmolalities for epididymal sperm from the pig (100 mOsm/kg), hamadryas baboon (range 50-125 mOsm/kg), and central rock rat (range 50-100 mOsm/kg), and the ejaculated sperm from the emu (50 mOsm/kg) and the Asian elephant (range 75-150 mOsm/kg). A solution of TALP-HEPES medium at 100 mOsm/kg would be suitable to obtain the maximal response in this range of mammals tested, though it would need to be diluted to at least 50 mOsm/kg when testing the viability of the emu sperm.

Effects of DHA-enriched hen egg yolk and L-cysteine supplementation on quality of cryopreserved boar semen

The objective of the present study was to determine the effects of docosahexaenoic acid (DHA)-enriched hen egg yolks and L-cysteine supplementation on the qualities of the cryopreserved boar semen. A total of 15 ejaculates from 5 Pietrain boars were divided into 4 groups according to the compositions of the freezing extenders used, that is, normal hen egg yolk (group I), DHA-enriched hen egg yolk (group II), normal hen egg yolk with 5 mmol L(-1) of cysteine supplementation (group III) and DHA-enriched hen egg yolk with 5 mmol L(-1) of cysteine supplementation (group IV). The semen was cryopreserved using controlled rate freezer and was thawed at 50 degrees C for 12 s. Progressive motility, sperm viability, acrosome integrity and functional integrity of sperm plasma membrane of the post-thawed semen were evaluated. The supplementation of L-cysteine in the freezing extender alone (group III) improved progressive motility (P < 0.05), and the supplementation of L-cysteine in combination with DHA-enriched hen egg yolk (group IV) improved both progressive motility (P < 0.05) and acrosome integrity (P < 0.01). The use of DHA-enriched hen egg yolk alone (group II) did not enhance any of the post-thawed semen qualities (P > 0.05). In conclusion, the supplementation of antioxidant L-cysteine alone or in combination with DHA-enriched hen egg yolk significantly improved the post-thawed semen qualities, especially progressive motility and acrosome integrity.

Identifying useable semen

The "predictors of useable semen" used in most commercial AI centers provide a very conservative estimate of the relative fertility of individual boars. Furthermore, the relatively high sperm numbers used in commercial AI practice (usually >3 x10(9) total sperm per dose of extended semen) usually compensate for reduced fertility, as can be demonstrated in some boars when lower numbers of sperm are used for AI. Differences in relative boar fertility are also masked by the widespread use of pooled semen for commercial AI in many countries. However, the need to continually improve the efficiency of pork production, suggests that commercial AI practice should involve increased use of boars with the highest genetic merit for important production traits. Necessarily, this must be linked to the use of fewer sperm per AI dose, fewer inseminations per sow bred, and hence more sows bred by these superior sires. In turn, this requires improved techniques for evaluating semen characteristics directly related to the fertilization process, such as IVM-IVF assays, analysis of seminal plasma protein markers, more discriminatory tests of sperm motility and morphology, with the goal of identifying high-index boars whose fertility is sustained when low numbers of sperm are used for AI. This paper reviews the current status of laboratory-based boar semen evaluation techniques that meet these criteria.

Study on the in vitro effect of zearalenone and alpha-zearalenol on boar sperm-zona pellucida interaction by hemizona assay application

The mycotoxin zearalenone (zen) impairs fertility in farm animals. The aim of the present study was to investigate the effect of zearalenone and its major metabolite (alpha-zearalenol) on boar semen binding capacity, under in vitro conditions. Extended boar semen was exposed to three different concentrations of zen and alpha-zen (40, 60 and 80 microg ml(-1) of semen) for 1 h. Afterwards, the semen was washed and incubated with homologous oocyte hemizona for 4 h. A significant decrease (P < 0.001) in the number of tightly attached spermatozoa on the hemizona was obtained at concentrations of 60 microg ml(-1) and 80 microg ml(-1) of zen and alpha-zen. In conclusion, zen and alpha-zen affected the sperm-zona interaction by reducing the ability of boar spermatozoa to bind to the zona pellucida.