Relationship between sperm quality traits and field-fertility of porcine semen

Identification and functional prediction of miRNAs that regulate ROS levels in dielectric barrier discharge plasma-treated boar spermatozoa

Dielectric barrier discharge (DBD) plasma regulates the levels of reactive oxygen species (ROS), which are critical for sperm quality. MicroRNAs (miRNAs) are non-coding single-stranded RNA molecules encoded by endogenous genes, which regulate post-transcriptional gene expression in animals. At present, it is unknown whether DBD plasma can regulate sperm ROS levels through miRNAs. To further understand the regulatory mechanism of DBD plasma on sperm ROS levels, miRNAs in fresh boar spermatozoa were detected using Illumina deep sequencing technology. We found that 25 known miRNAs and 50 novel miRNAs were significantly upregulated, and 14 known miRNAs and 74 novel miRNAs were significantly downregulated in DBD plasma-treated spermatozoa. Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis showed that target genes of differentially expressed miRNAs were involved in many activities and pathways associated with antioxidants. We verified that DBD plasma significantly increased boar sperm quality and reduced ROS levels. These results suggest that DBD plasma can improve sperm quality by regulating ROS levels via miRNAs. Our findings provide a potential strategy to improve sperm quality through miRNA-targeted regulation of ROS, which helps to increase male reproduction and protect cryopreserved semen in clinical practice.

Artificial intelligence and porcine breeding

Livestock management is evolving into a new era, characterized by the analysis of vast quantities of data (Big Data) collected from both traditional breeding methods and new technologies such as sensors, automated monitoring system, and advanced analytics. Artificial intelligence (A-In), which refers to the capability of machines to mimic human intelligence, including subfields like machine learning and deep learning, is playing a pivotal role in this transformation. A wide array of A-In techniques, successfully employed in various industrial and scientific contexts, are now being integrated into mainstream livestock management practices. In the case of swine breeding, while traditional methods have yielded considerable success, the increasing amount of information requires the adoption of new technologies such as A-In to drive productivity, enhance animal welfare, and reduce environmental impact. Current findings suggest that these techniques have the potential to match or exceed the performance of traditional methods, often being more scalable in terms of efficiency and sustainability within the breeding industry. This review provides insights into the application of A-In in porcine breeding, from the perspectives of both sows (including welfare and reproductive management) and boars (including semen quality and health), and explores new approaches which are already being applied in other species.

Normal sperm head morphometric reference values in fertile Asian males

Sperm head morphology is crucial for male factor infertility diagnosis and assessment of male reproductive potential. Several criteria are available to analyze sperm head morphology, but they are limited by poor methodology comparability and population applicability. This study aimed to explore comprehensive and new normal morphometric reference values for spermatozoa heads in fertile Asian males. An automated sperm morphology analysis system captured 23 152 stained spermatozoa from confirmed fertile males. Of these samples, 1856 sperm head images were annotated by three experienced laboratory technicians as "normal". We employed 14 novel morphometric features to describe sperm head size (head length, head width, length/width ratio, and girth), shape (ellipse intersection over union, girth intersection over union, short-axis symmetry, and long-axis symmetry), area (head, acrosome, postacrosomal areas, and acrosome area ratio), and degrees of acrosome and nuclear uniformity. This straight-forward method for the morphometric analysis of sperm by accurate visual measurements is clinically applicable. The measured parameters present valuable information to establish morphometric reference intervals for normal sperm heads in fertile Asian males. The presented detailed measurement data will be valuable for interlaboratory comparisons and technician training. In vitro fertilization and andrology laboratory technicians can use these parameters to perform objective morphology evaluation when assessing male fertilization potential.

Target silencing of porcine SPAG6 and PPP1CC by shRNA attenuated sperm motility

The quality of sperm significantly influences the reproductive efficiency of pig herds. High-quality sperm is necessary for efficient fertilization and to maximize the litter numbers in commercial pig farming. However, the understanding of genes regulating porcine sperm motility and viability is limited. In this study, we validated porcine sperm/Sertoli-specific promoters through the luciferase reporter system and identified vital genes for sperm quality via loss-of-function means. Further, the shRNAs driven by the ACE and SP-10 promoters were used to knockdown the SPAG6 and PPP1CC genes which were provisionally important for sperm quality. We assessed the effects of SPAG6 and PPP1CC knockdown on sperm motility by using the sperm quality analyzer and flow cytometry. The results showed that the ACE promoter is active in both porcine Sertoli cells and sperms, whereas the SP-10 promoter is operating exclusively in sperm cells. Targeted interference with SPAG6 and PPP1CC expression in sperm cells decreases the motility and increases apoptosis rates in porcine sperms. These findings not only offer new genetic tools for targeting male germ cells but also highlight the crucial roles of SPAG6 and PPP1CC in porcine sperm function.

Genome-Wide Association Analysis of Semen Characteristics in Piétrain Boars

Since artificial insemination is common practice in pig breeding, the quality and persistence of the semen are decisive for the usability of individual boars. In the current study, genome-wide association analyses were performed to investigate the genetic variability underlying phenotypic variations in semen characteristics. These traits comprise sperm morphology and sperm motility under different temporal and thermal storage conditions, in addition to standard semen quality parameters. Two consecutive samples of the fourth and fifth ejaculates from the same boar were comprehensively analyzed in a genotyped Piétrain boar population. A total of 13 genomic regions on different chromosomes were identified that contain single-nucleotide polymorphisms significantly associated with these traits. Subsequent analysis of the genomic regions revealed candidate genes described to be involved in spermatogenesis, such as FOXL3, GPER1, PDGFA, PRKAR1B, SNRK, SUN1, and TSPO, and sperm motility, including ARRDC4, CEP78, DNAAF5, and GPER1. Some of these genes were also associated with male fertility or infertility in mammals (e.g., CEP78, GPER1). The analyses based on these laboriously determined and valuable phenotypes contribute to a better understanding of the genetic background of male fertility traits in pigs and could prospectively contribute to the improvement of sperm quality through breeding approaches.

Sperm proteomic landscape is altered in breeding bulls with greater sperm DNA fragmentation index

Although, it is well understood that sperm DNA damage is associated with infertility, the molecular details of how damaged sperm DNA affects fertility are not fully elucidated. Since sperm proteins play an important role in fertilization and post-fertilization events, the present study aimed to identify the sperm proteomic alterations in bulls with high sperm DNA Fragmentation Index (DFI%). Semen from Holstein-Friesian crossbred breeding bulls (n = 50) was subjected to Sperm Chromatin Structure Assay. Based on DFI%, bulls were classified into either high- (HDFI; n = 6), or low-DFI (LDFI; n = 6) and their spermatozoa were subjected to high throughput proteomic analysis. Liquid chromatography and mass spectrometry analysis identified 4567 proteins in bull spermatozoa. A total of 2660 proteins were found common to both the groups, while 1193 and 714 proteins were unique to HDFI and LDFI group, respectively. A total of 265 proteins were up regulated and 262 proteins were down regulated in HDFI group. It was found that proteins involved in capacitation [heparin binding (molecular function), ERK1 and ERK2 cascade (biological process), PI3K-Akt signalling (pathway), Jak-STAT signalling (pathway)], spermatogenesis [TLR signalling (pathway), gamete generation (biological process)] and DNA repair mechanism (biological process) were significantly altered in the bulls with high DFI%.

Relationship between biochemical parameters and paraoxonase 1 activity of boar seminal plasma and semen quality

The aim of this study was to examine the biochemical components and the parameters of antioxidant protection in the seminal plasma (SP) of boars, as well as their relationship with semen quality parameters. Thirty-six boars were included in the study, whose ejaculates were divided into two groups: Group I (good quality semen, > 70% progressively motile sperm, < 20% spermatozoa with abnormal morphology, n = 16), and Group II (poor quality semen, < 70% progressively motile sperm, > 20% spermatozoa with abnormal morphology, n = 20). Significantly higher concentrations of ionized calcium (iCa), total cholesterol (TC), lactate-dehydrogenase (LDH) activity, as well as significantly higher values ​​of antioxidant protection parameters: thiol groups (-SH), paraoxonase 1 (PON1), and total antioxidant capacity (TAC) ) were found in the good quality semen, while higher phosphorus (P) concentrations and increased alkaline-phosphatase (ALP) activity were found in the semen of poor quality. A negative correlation of total and progressive sperm motility with P and ALP was found in all examined semen samples, while a positive correlation was found with PON1 and TAC. The percentage of fast sperm cells positively correlated with iCa, chlorine (Cl), lactate, LDH and TAC, while a negative correlation was found with P, magnesium (Mg) and the enzyme creatine-kinase (CK). The percentage of immobile sperm positively correlated with P and ALP, and negatively correlated with TC, CK, PON1 and TAC. Elevated values ​​of PON1 and TAC in SP and a positive correlation with sperm motility indicate the possible use of these parameters as sensitive biomarkers of boar semen quality. To the best of our knowledge there are no published data on association between PON1 activity and boar semen quality.

Sperm capacitation as a predictor of boar fertility

Prediction of a boar's fertility level has great economic importance for sow herds. After standard sperm morphology and motility metrics are met, approximately 25% of boars have less than 80% conception rates. Due in part to the many factors involved in the fertilization process, a multifactorial model incorporating multiple relevant sperm physiology factors will likely lead to increased understanding of boar fertility. Here we review the current literature on boar sperm capacitation as a predictor of boar fertility. While limited, several studies have provided correlations between the percentage of sperm in an ejaculate that are capable of undergoing sperm capacitation in a chemically defined media and artificial insemination field fertility as well as proteome and other methods. Work summarized here underscores the need for further understanding of boar fertility.

Cluster analysis and potential influencing factors of boars with different fertility

The fertility of boars is intimately tied to the pig farm's economic benefits. This study aimed to rapidly categorize boars of different fertility and investigate the factors influencing the categorization using the production data in a large pig farm in northern China, including 11,163 semen collection records of Yorkshire boars (215), 11,163 breeding records and 8770 records of farrowing performance of Yorkshire sows (4505), as well as 4720 records of selection indices (sire line index and dam line index) for boars and sows (215 and 4505) between 2017 and 2020. The boar population was classified by two-step cluster analysis, followed by factor analysis to minimize the dimensionality of data variables and eliminate multicollinearity, and then using ordinal logistic regression model to investigate the risk variables impacting boar fertility categorization. Results showed that the two-step clustering divided the 215 boars into three subgroups: high-fertility (n = 61, 28.4%), medium-fertility (n = 127, 59.1%) and low-fertility (n = 27, 12.6%). The high-fertility boars were shown to be substantially greater than the medium-fertility or low-fertility boars (p < 0.05) in average total litter size, number of born alive, and number of healthy piglets of mated sows. Compared with low-fertility boars, the high-fertility boars were also significantly higher (p < 0.05) in the pregnancy rate and farrowing rate of mated sows. However, the three boar subgroups showed no difference (p > 0.05) in semen quality information (average sperm motility, average sperm density, and average sperm volume). Collinearity diagnosis indicated severe multicollinearity among the 20 data variables, which were reduced to 8 factor variables (factors 1-8) by factor analysis, and further collinearity diagnosis exhibited no multicollinearity among the 8 factor variables. Ordered logistic regression analysis revealed a significant and positive correlation (p < 0.05) of boar fertility with factor 2 (average total litter size, number of born alive, number of healthy piglets), factor 4 (average number of weak piglets and average weak piglet rate), factor 6 (sire line index of boars and dam line index of boars), factor 8 (pregnancy rate and farrowing rate), highlighting factor 2 as the most important factor influencing the classification of boar fertility. Our results indicate that the two-step cluster analysis can be used as a simple and effective method to screen boars with different fertility and that farm producers should pay attention to the recording of the reproductive performance of the mated sows due to its role as the risk factor for classification of boar fertility.

Seminal plasma metabolomics analysis of differences in liquid preservation ability of boar sperm

The preservation of semen is pivotal in animal reproduction to ensure successful fertilization and genetic improvement of livestock and poultry. However, investigating the underlying causes of differences in sperm liquid preservation ability and identifying relevant biomarkers remains a challenge. This study utilized liquid chromatography-mass spectrometry (LC-MS) to analyze the metabolite composition of seminal plasma (SP) from two groups with extreme differences in sperm liquid preservation ability. The two groups namely the good liquid preservation ability (GPA) and the poor preservation ability (PPA). The aim was to explore the relationship between metabolite composition in SP and sperm liquid preservation ability, and to identify candidate biomarkers associated with this ability of sperm. The results revealed the identification of 756 metabolites and 70 differentially expressed metabolites (DEM) in the SP from two groups of boar semen with differing liquid preservation abilities at 17 °C. The majority of identified metabolites in the SP belonged to organic acids and derivatives as well as lipids and lipid-like molecules. The DEM in the SP primarily consisted of amino acids, peptides, and analogs. The Kyoto Encyclopedia of Genes and Genomes analysis also demonstrated that the DEM are mainly concentrated in amino acid synthesis and metabolism-related pathways (P < 0.05). Furthermore, eleven key metabolites were identified and six target amino acids were verified, and the results were consistent with the non-targeted metabolic analysis. These findings indicated that amino acids and their associated pathways play a potential role in determining boar sperm quality and liquid preservation ability. D-proline, arginine, L-citrulline, phenylalanine, leucine, DL-proline, DL-serine, and indole may serve as potential biomarkers for early assessment of boar sperm liquid preservation ability. The findings of this study are helpful in understanding the causes and mechanisms of differences in the liquid preservation ability of boar sperm, and provide valuable insights for improving semen quality assessment methods and developing novel extenders or protocols.

Predicting fertility from sperm motility landscapes

Understanding the organisational principles of sperm motility has both evolutionary and applied impact. The emergence of computer aided systems in this field came with the promise of automated quantification and classification, potentially improving our understanding of the determinants of reproductive success. Yet, nowadays the relationship between sperm variability and fertility remains unclear. Here, we characterize pig sperm motility using t-SNE, an embedding method adequate to study behavioural variability. T-SNE reveals a hierarchical organization of sperm motility across ejaculates and individuals, enabling accurate fertility predictions by means of Bayesian logistic regression. Our results show that sperm motility features, like high-speed and straight-lined motion, correlate positively with fertility and are more relevant than other sources of variability. We propose the combined use of embedding methods with Bayesian inference frameworks in order to achieve a better understanding of the relationship between fertility and sperm motility in animals, including humans.

Dimension reduction methods on porcine sperm motility landscapes reveal heterogeneity and hierarchy in sperm movement behavior and show high-speed and straight-lined motion as predictive features of fertility.

Alginate oligosaccharides increase boar semen quality by affecting gut microbiota and metabolites in blood and sperm

Alginate oligosaccharides (AOS), natural polymers from brown seaweeds (such as Laminaria japonica, Undaria pinnatifida, and Sargassum fusiforme), have been reported to possess many beneficial advantages for health. In the current study, after 9 weeks of dietary supplementation, AOS 10 mg/kg group (AOS 10) group increased boar sperm motility from 87.8% to 93.5%, p < 0.05. Moreover, AOS10 increased the relative abundances of Bifidobacterium, Coprococcus, Butyricicoccus (1.3–2.3-fold; p < 0.05) to increase the beneficial blood and sperm metabolites (1.2–1.6-fold; p < 0.05), and important sperm proteins such as gelsolin, Zn-alpha2 glycoprotein, Cation Channel Sperm-Associated Protein, outer dense fiber of sperm tails, etc. (1.5–2.2-fold; p < 0.05). AOS had a long-term beneficial advantage on boar semen quality by the increase in semen volume (175 vs. 160 ml/ejaculation, p < 0.05). AOS may be used as dietary additives for improving semen quality.

Parenteral supplementation of Cu, Zn and Mn enhances boars' sperm quality

INTRODUCTION

The trace elements concentrations of blood might play a key role in the trace element concentration of seminal plasma, as well as in the improvement of semen volume and sperm morphology in boars.

OBJECTIVE

To assess the effect of supplementation of Cu, Zn and Mn on their concentrations in blood serum and seminal plasma and sperm quality in boars.

METHODS

Eighteen boars of the Duroc Jersey breed were selected and their blood and semen (54 ejaculates before supplementation) were extracted. Coinciding with the third sampling and after of blood taken, the boars were supplemented subcutaneously with 37.5 mg of Cu, 75 mg of Zn and 37.5 mg of Mn; 40 days after the supplementation the fourth sampling was taken. Cu and Zn concentrations in blood serum and seminal plasma were determined by atomic absorption spectrophotometry, while the sperm pathologies were determined by microscopy and the concentrations of Cu and Zn in blood serum and seminal plasma, and semen pathologies were compared using the t-Student test for paired samples. A simple linear correlation was made between the minerals concentration in seminal plasma with the percentage of spermatozoa with abnormal forms.

RESULTS

Although the concentrations of Zn in blood serum did not show differences between sampling periods (P < 0.05), they were significantly higher (P < 0.01) in the seminal plasma after supplementation as compared to its levels before supplementation. In addition, the concentrations of Cu and Zn in seminal plasma were increased (P < 0.01), and the total spermatic pathologies were reduced; especially those of the head, neck and intermediate part of the tail (P < 0.001). Besides, macrocephaly, double head and broken acrosome were the most common pathologies (P < 0.05). Moreover, parenteral supplementation of Cu, Zn and Mn was a protective factor to the presentation of ejaculates with abnormal sperm percentages higher than 10% (χ2 = 6.1544; P = 0.0131). The prevalence of abnormal shapes of boars' sperm before supplementation was 0.40; after supplementation the answer was 0.05 and the prevalence ratio was 0.13 with a confidence interval of 95% from 0.01 to 0.94. Moreover, Zn concentrations in blood serum were not correlated with those of the seminal plasma (P > 0.05, r = - 0.0353); however, the concentrations of Cu in both fluids were correlated (P < 0.05, r = 0.2254). In addition, the Zn values in the seminal plasma and the percentage of abnormal spermatozoa had a negative and highly significant correlation (P < 0.0001, r = - 0.5628). However, the Cu concentrations in the semen were not significantly correlated with the abnormal sperm forms (P > 0.05, r = 0.0200).

CONCLUSION

From the present study it can be concluded that in boars fed with diets that meeting their requirements in trace minerals according to NRC (2012) [1], parenteral supplementation of 37.5 mg of Cu, 75 mg of Zn and 37.5 mg of Mn increased the Zn concentrations in the seminal plasma and reduced the sperm pathologies, which resulted in an increase of the boars' sperm quality.

The Use of Animal's Body, Scrotal Temperature and Motion Monitoring in Evaluating Boar Semen Production Capacity

Biomedical measurements by specialized technological equipment have been used in farm animals to collect information about nutrition, behavior and welfare. This study investigates the relation of semen quality (CASA analysis, viability, morphology, membrane biochemical activity and DNA fragmentation) with boar behavior during ejaculation. Sensors were placed on the boar’s body. Movement features were collected using an inertial measurement unit (IMU), comprising an accelerometer, a gyroscope and a magnetometer. Boar, scrotal and dummy temperatures were measured by an infrared (IR) camera and an IR thermometer, while the face salivation of the boar was recorded by a moisture meter (also based on IR technology). All signals and images were logged on a mobile device (smartphone or tablet) using a Bluetooth connection and then transferred wirelessly to the cloud. The data files were then processed using scripts in MATLAB 2021a (MathWorks, Natick, Massachusetts) to derive the necessary indices. Ninety-four ejaculates from five boars were analyzed in this study. The statistical analysis was performed in the Statistics and Machine Learning Toolbox of MATLAB 2021a using a linear mixed effects model. Significant and strong negative correlations (R2 > 0.5, p ≤ 0.05) were observed between boar, dummy and scrotal temperature with the progressive, rapid and slow movement of spermatozoa, VCL (curvilinear velocity), VSL (straight line velocity) and ALH (amplitude of lateral head displacement) kinematics. The volume of the ejaculate was correlated with the scrotal and dummy temperature. Dummy’s temperature was negatively correlated with BCF (beat/cross-frequency), viability and total time of ejaculation, while it was positively correlated with abnormal morphology. Body temperature was negatively correlated with BCF. Positive correlations were noticed between VAP (average path velocity) and total time of ejaculation with body acceleration features, as well as between the overall dynamic body acceleration (ODBA) and total time of ejaculation. In conclusion, the use of biomedical sensors can support the evaluation of boar sperm production capacity, providing valuable information about semen quality.

Research Note: Dietary supplementation with pyrroloquinoline quinone disodium (PQQ.Na2) improves oxidative status and semen quality in aging layer breeder roosters

As the antioxidant capacity of sperm declines with age in roosters, the objective of the present study was to determine the effects of different levels of pyrroloquinoline quinone disodium (PQQ.Na₂) on antioxidative and sperm quality parameters of aging layer breeder roosters. A total of ninety-six 63-wk-old Jinghong No. 1 layer breeder roosters were randomly assigned to 4 treatments (0, 0.5, 1, 2 mg/kg PQQ.Na₂) for 6 wk. Antioxidant activity and semen parameters were assessed biweekly. The dietary administration of PQQ.Na₂ significantly increased semen quality (semen volume, sperm motility, straightness, progressive motility, curvilinear velocity, straight-line velocity, and amplitude of lateral head displacement) and antioxidant capacity (T-SOD, GSH-Px, hydroxyl radical scavenging ability, and/or superoxide scavenging capacity) in seminal plasma in aging layer breeder roosters. Whereas, PQQ.Na₂ supplementations significantly decreased malondialdehyde (MDA) concentration in seminal plasma in aging layer breeder roosters. Supplementation with 1 mg/kg dietary PQQ.Na₂ as an antioxidant supplement could increase sperm quality and antioxidant activity of aging layer breeder roosters, while a higher dose (2 mg/kg) did not result in further increment.

The Usefulness of Sexual Behaviour Assessment at the Beginning of Service to Predict the Suitability of Boars for Artificial Insemination

Simple Summary

Boars producing ejaculates of high quality and shortest duration are particularly valuable; this aspect can be the primary factor in inbreeding development and improvement of swine utilization. It is important to develop objective ways to describe the sexual activity of various breeds of boars and its application and effectiveness in conducting artificial insemination. The results of this study indicate that the time from entering the arena until achieving an erection, which is assessed at the beginning of a boar’s breeding utilization, may be used to predict a boar’s future libido. There was an association between the level of libido and ejaculate characteristics. Boars requiring the most time to begin ejaculation produce ejaculates with a higher sperm concentration and number.

Abstract

Parameters of sexual activity were determined in 49 young boars used for artificial insemination, four times at three-month intervals. The parameters included the time from entering the arena until mounting the phantom; the time from mounting the phantom until achieving erection; the time from achieving full erection until the start of ejaculation; duration of ejaculation; and the number of times the boar mounted the phantom. Characteristics of the ejaculates were also assessed. The libido parameter associated with the greatest efficacy of artificial insemination was the effectiveness of artificial insemination service, the time from entering the arena until the start of ejaculation. The significance of this trait for predicting ejaculation performance was analysed. The libido characteristics were classified into three categories: boars with a short reaction time to the phantom, boars with an intermediate reaction time, and boars with a long reaction time. For these groups, the characteristics of ejaculates collected at the start of the period during which ejaculates were collected and after three, six and nine months were determined. The sexual experience of boars was not associated with the expression of sexual behaviour because young boars during their first three months of ejaculate collections required less time to initiate ejaculation. The ejaculates with the greatest utility were obtained after six months of service. These ejaculates had the largest volume (255.22 mL), and the most insemination doses could be prepared from these ejaculates. On average, more than 23 insemination doses were prepared from ejaculates collected after six months of semen collections, which is about four doses more than from ejaculates collected at the start of artificial insemination service (p < 0.01).The time from entering the arena to beginning ejaculation can be used to predict a boar’s future libido. A relationship was shown between the level of libido and ejaculate characteristics. The ejaculates of the boars which needed the longest time to begin ejaculation at the start of semen collections had the greatest sperm concentration and number. In group 3, the boars’ejaculates contained about 6–9 × 10⁹ more sperm than the ejaculates of boars from group 1. After six months of the experimental period, the difference was nearly 15 × 10⁹ sperm (p < 0.05), and after nine months, it exceeded 22 × 10⁹ sperm (p < 0.01).

Monitoring the reactive oxygen species in spermatozoa during liquid storage of boar semen and its correlation with sperm motility, free thiol content and seasonality

Oxidative stress is an important factor affecting the quality of spermatozoa during liquid storage of boar semen; however, monitoring of reactive oxygen species (ROS) that provides direct insight into the oxidative status is not yet attempted. This study aimed to monitor ROS in boar sperm during liquid semen storage to determine its correlation with sperm motility and free thiol (SH) content, and seasonality. Ejaculate was collected from mature Duroc boars in a commercial farm in autumn and spring, diluted in Mulberry III extender, stored at 15°C, and examined daily for sperm ROS level, SH content and motility. The ROS levels in spermatozoa prepared during autumn and spring were constantly low until days 4 and 5 of storage, respectively, which thereafter progressively increased in association with the loss of sperm motility. The increased sperm ROS level correlated with the higher SH level and lower motility, which was accentuated from day 4 of storage and was higher in September, or early autumn. This study indicates that increased sperm ROS levels during liquid storage results in oxidative damage, causing loss of sperm motility, presumably through decreased sperm viability, suggesting that sperm ROS monitoring effectively evaluates the quality of boar semen.

Relationship between Fertility Traits and Kinematics in Clusters of Boar Ejaculates

Simple Summary

Swine reproduction efficiency is determined by the fertility potential of the sow and sperm quality. The objective of this study is to compare boar sperm motility and kinematic features to evaluate their relationships with reproductive success after artificial insemination (AI). In this study, the movement patterns of boar ejaculates were analyzed by a computer-assisted semen analysis (CASA)-Mot system, and the kinematic values of ejaculate clusters were assessed. The semen of the Pietrain boars showed more linear trajectory of the spermatozoa, while curvilinear velocity and oscillatory movement characterized the semen of the Duroc × Pietrain boars. The offspring of sows inseminated with Pietrain boars showed significantly lower number of stillbirths. In addition, ejaculate grouping into clusters did not have a predictive capacity on litter size variables. Nevertheless, the kinematic variables of the ejaculate may have a predictive, albeit reduced, capacity regarding litter size variables. The results of this study therefore open up possibilities for future assessments of fertility.

Abstract

The aim was to determine the relationship between kinematic parameters of boar spermatozoa and fertility rates of sow, as well as to assess the effect of sperm clusters on the fertility capacity of the ejaculate. Semen samples were collected from 11 sexually mature boars. Samples were analyzed by an ISAS^®v1 CASA-Mot system for eight kinematic parameters. Ejaculate clusters were characterized using multivariate procedures, such as principal factors (PFs) analysis and clustering methods (the k-means model). Four different ejaculate clusters were identified from two kinematic PFs which involved linear trajectory and velocity. There were differences (p < 0.05) between the sperm kinematic variables by sire line. There was no statistical difference (p > 0.05) between dam lines and ejaculate clusters in fertility variables. The discriminant ability of the different kinematics of sperm variables to predict litter size fertility was analyzed using receiver operating characteristics (ROC) curve analysis. Curvilinear velocity (VCL), average path velocity (VAP), amplitude of lateral head displacement (ALH), and beat-cross frequency (BCF) showed significant, albeit limited, predictive capacity for litter size fertility variables (range: 0.55–0.58 area under curve, AUC). The kinematic analysis of the ejaculates in clusters did not have a predictive capacity for litter size variables.

Effect of Boar Sperm Proteins and Quality Changes on Field Fertility

Simple Summary

Artificial insemination with extended liquid boar semen is widely used in the swine industry. The identification of the relationship between boar sperm characteristics and fertility could be of substantial importance to reproduction management. This study evaluated the relationship between boar sperm characteristics and sperm/seminal plasma proteins with main parameters of field fertility. Immotile spermatozoa and spermatozoa with biochemically active plasma membranes affected the number of live-born piglets and litter size of ≥12 piglets. The proteins osteopontin 70 and glutathione peroxidase 5, both separately and in combination, affected the farrowing rate. The combination of immotile sperm and protein osteopontin 70 explained the variation regarding litter size with ≥12 piglets. In conclusion, the evaluation of semen quality variables combined with the evaluation of specific sperm or seminal plasma proteins could provide useful information on in vivo fertilizing capacity of semen doses.

Abstract

This study aimed to evaluate boar sperm characteristics and proteins, in relation to their importance regarding in vivo fertility. Sixty-five ejaculates were used and 468 sows (parity ≥ 2) were inseminated. Sperm CASA kinetics, morphology, viability, DNA fragmentation, mitochondrial membrane potential, sperm membrane biochemical activity (HOST) and sperm proteins (Heat Shock Protein 90-HSP90, glutathione peroxidase-5-GPX5, Osteopontin 70-OPN70) were assessed and related to field fertility (number of live-born piglets—NLBP, litter size ≥ 12 piglets—LS, farrowing rate—FR). Statistical analysis was conducted with simple and multiple regression models. Simple regression analysis showed that immotile sperm (IM) significantly affected the NLBP and LS, explaining 6.7% and 6.5% of their variation, respectively. The HOST positive spermatozoa significantly affected the NLBP and LS, explaining 24.5% and 7.8% of their variation, respectively. Similarly, sperm with activated mitochondria significantly affected the NLBP, explaining 13.5% of its variation. Moreover, the OPN70 affected LS and FR, explaining 7.5% and 10.8% of their variation, respectively. Sperm GPX5 protein affected FR, explaining 6.7% of its variation. Multiple regression analysis showed that the combination of IM and/OPN70 explains 13.0% of the variation regarding LS, and the combination of GPX5 and OPN70 explains 13.6% of the variation regarding FR. In conclusion, the estimation of parameters IM, membrane biochemical activity, mitochondrial membrane potential, OPN and GPX5 can provide useful information regarding semen doses for field fertility.

Effect of Copper Sulphate and Cadmium Chloride on Non-Human Primate Sperm Function In Vitro

In order to address the large percentage of unexplained male infertility in humans, more detailed investigations using sperm functional tests are needed to identify possible causes for compromised fertility. Since many environmental and lifestyle factors might be contributing to infertility, future studies aiming to elucidate the effect of such factors on male fertility will need the use of appropriate research models. The current study aimed to assess the effects of two heavy metals, namely copper sulphate, and cadmium chloride, on non-human primate (NHP) sperm function in order to establish the possibility of using these primate species as models for reproductive studies. Our combined results indicated that the functionality of NHP spermatozoa is inhibited by the two heavy metals investigated. After in vitro exposure, detrimental effects, and significant lowered values (p < 0.05) were obtained for sperm motility, viability and vitality, acrosome intactness, and hyperactivation. These metals, at the tested higher concentrations, therefore, have the ability to impair sperm quality thereby affecting sperm fertilizing capability in both humans and NHPs.

Predictive Capacity of Boar Sperm Morphometry and Morphometric Sub-Populations on Reproductive Success after Artificial Insemination

Simple Summary

The efficiency of swine production measured as litter size influences the profitability of the pig industry. Furthermore, sow fertility potential depends in part on the boar semen quality and reproductive efficiency. The objective of this study is to compare boar sperm head size and morphometric features of shape to evaluate their relationships with reproductive success after artificial insemination (AI). A morphometric analysis of boar ejaculate reveals morphometrically separate sub-populations. The differences between sub-populations are displayed for sperm head size. In addition, sperm clustering into sub-populations did not have a predictive capacity on litter size variables. Nevertheless, the morphometric variables of the sperm may have a predictive, albeit reduced, capacity regarding litter size variables. The results of this study therefore open up possibilities for future assessments of fertility.

Abstract

The aim of the study was to compare the morphometric features of sperm head size and shape from the Pietrain line and the Duroc × Pietrain boar crossbred terminal lines, and to evaluate their relationship with reproductive success after artificial insemination of sows produced from crossbreeding the York, Landrace and Pietrain breeds. Semen samples were collected from 11 sexually mature boars. Only ejaculates with greater than 70% motility rate and <15% of abnormal sperm were used for artificial inseminations (AI) and included in the study. Samples were analyzed using an ISAS^®v1 computer-assisted sperm analysis system for eight morphometric parameters of head shape and size (CASA-Morph). Sub-populations of morphometric ejaculates were characterized using multivariate procedures, such as principal component (PC) analysis and clustering methods (k-means model). Four different ejaculate sub-populations were identified from two PCs that involved the head shape and size of the spermatozoa. The discriminant ability of the different morphometric sperm variables to predict sow litter size was analyzed using a receiver operating characteristics (ROC) curve analysis. Sperm head length, ellipticity, elongation, and regularity showed significant predictive capacity on litter size (0.59, 0.59, 0.60, and 0.56 area under curve (AUC), respectively). The morphometric sperm sub-populations were not related to sow litter size.

Effect of Toxoplasma gondii on Ram Sperm Quality After Experimental Infection

The aim of this study was to investigate the effect of experimental Toxoplasma gondii infection on ram sperm quality. Five months old, pre-pubertal, rams were divided into four groups (n = 8 per group). Group A was the control group; the remaining animals received per os (p.o.) 5000 oocysts per ram. Group B did not receive treatment post-infection (p.i.). Group C received sulphadimidine (intermuscular injection (i.m.) 33 mg/kg for eight days; every 48 hrs) two months p.i. and Group D received the same drug twice (24 hours p.i. and two months later). Blood samples were collected every 15 days to detect serum immunoglobulin G (IgG). Epididymal sperm samples were analyzed for concentration, kinetics, morphology/viability, functional membrane integrity, DNA integrity, and the presence of parasite DNA. Histopathological examination was performed on the testes. The IgG titres in infected groups raised two weeks p.i. and remained high for four months. Higher values were noticed in viability and functional membrane integrity in positive spermatozoa in the control group compared to other groups, level of significance p < 0.05. Abnormal sperm was higher in groups C and D vs. A and C vs. B (p < 0.05). T. gondii DNA was detected in three sperm samples of the infected rams (12.5%). Histopathology revealed similar findings with little variation among all infected groups, characterized mostly by increased interstitial connective tissue, non-purulent inflammation, and presence of seminiferous tubules with spermatogenic cell depletion, which increased gradually from D to C and B groups. In conclusion Toxoplasmosis in pre-pubertal age negatively affected mature ram sperm quality, while sulphadimidine administration failed to alter this.

Iron Oxide Nanoparticles as an Alternative to Antibiotics Additive on Extended Boar Semen

This study examined the effect of Fe₃O₄ nanoparticles on boar semen. Beltsville thawing solution without antibiotics was used to extend ejaculates from 5 boars (4 ejaculates/boar). Semen samples of control group (C) and group with Fe₃O₄ (Fe; 0.192 mg/mL semen) were incubated under routine boar semen storage temperature (17 °C) for 0.5 h and nanoparticles were removed by a magnetic field. Before and after treatment, aliquots of all groups were cultured using standard microbiological methods. The samples after treatment were stored (17 °C) for 48 h and sperm parameters (computer-assisted sperm analyzer (CASA) variables; morphology; viability; hypo-osmotic swelling test (HOST); DNA integrity) were evaluated at storage times 0, 24, 48 h. Semen data were analyzed by a repeated measures mixed model and microbial data with Student’s t-test for paired samples. Regarding CASA parameters, Fe group did not differ from C at any time point. In group C, total motility after 24 h and progressive motility after 48 h of storage decreased significantly compared to 0 h. In group Fe, linearity (LIN) after 48 h and head abnormalities after 24 h of storage increased significantly compared to 0 h. The microbiological results revealed a significant reduction of the bacterial load in group Fe compared to control at both 24 and 48 h. In conclusion, the use of Fe₃O₄ nanoparticles during semen processing provided a slight anti-microbiological effect with no adverse effects on sperm characteristics.

Effect of artificial insemination and natural mating on reproductive parameters in pigs of warm-humid climate region

Artificial insemination is a popular assisted reproductive technology that ensures transfer of genetic information from animal to animal. This study was meant to evaluate the influence of artificial insemination and natural mating on selected reproductive parameters. Five hybrid females of Duroc-landrace line were selected while 3 boars were used for the mating. Fresh semen was collected from 2 hybrid boars of Yorkshire-Landrace and Yorkshire-Pietrain line and the third boar - a Durocbreed (control) was used to stimulate the sows into oestrus and mate them naturally. Landrace-Yorkshire had shorter time for semen release than Pietrain-Yorkshire breed at first and second time of collecting the semen. Similarly, live born piglets of artificial insemination served 24% higher than natural mating. Therefore, a well-timed artificial insemination method using fresh semen would improve the number of piglets at parturition.

Tropical summer induces DNA fragmentation in boar spermatozoa: implications for evaluating seasonal infertility

Summer infertility continues to undermine pig productivity, costing the pig industry millions in annual losses. The boar's inefficient capacity to sweat, non-pendulous scrotum and the extensive use of European breeds in tropical conditions, can make the boar particularly vulnerable to the effects of heat stress; however, the link between summer heat stress and boar sperm DNA damage has not yet been demonstrated. Semen from five Large White boars was collected and evaluated during the early dry, late dry and peak wet seasons to determine the effect of seasonal heat stress on the quality and DNA integrity of boar spermatozoa. DNA damage in spermatozoa during the peak wet was 16-fold greater than during the early dry and nearly 9-fold greater than during the late dry season. Sperm concentration was 1.6-fold lower in the peak wet than early dry whereas no difference was found across several motility parameters as determined by computer-assisted sperm analysis. These results demonstrate that tropical summer (peak wet season) induces DNA damage and reduces concentration without depressing motility in boar spermatozoa, suggesting that traditional methods of evaluating sperm motility may not detect inherently compromised spermatozoa. Boar management strategies (such as antioxidant supplementation) need to be developed to specifically mitigate this problem.

The effect of porcine circovirus type 2 (PCV2) vaccination of male piglets on sperm quality at the age of puberty

The objective of the study was to investigate the effect of porcine circovirus type 2 (PCV2) vaccination in piglets on sperm quality of young boars. A total of 136 sows were divided in four groups of 34 animals each (17 vaccinated with Circovac®, Merial and 17 unvaccinated in each group). A total of 1 200 piglets were selected, half of which were vaccinated against PCV2 on the 21st day (Porcilis® PCV, MSD) and the other half was left unvaccinated. Four groups of 300 pigs each were formed as follows: PS group (vaccinated sows + piglets), S group (vaccinated sows + unvaccinated piglets), P group (unvaccinated sows + vaccinated piglets), C group (unvaccinated sows + piglets). Furthermore, 80 boars (20 piglets per group) were selected and slaughtered at the age of 5.5 months and weight of 95 ± 5.5 kg and their epididymal sperm was collected and evaluated for motility and kinetics, concentration and morphology. Additionally, 10 pigs from each group were used for blood sampling and serological testing for PCV2 IgM and IgG antibodies at the age of 21, 70, 110 and 150 days. The IgG and IgM patterns suggested that the piglets were coming into contact with PCV2 early in life. The S group demonstrated significantly lower curvilinear velocity (VCL, μm/s), amplitude of lateral head displacement (ALH, μm) and significantly higher head abnormalities (%) compared to other groups (P< 0.05). In conclusion, vaccinated young boars showed some improved epididymal sperm kinetic indices and head morphology.

Serum and Seminal Plasma Element Concentrations in Relation to Semen Quality in Duroc Boars

Element concentrations in serum and seminal plasma were studied in Duroc boars with different semen quality characteristics. Based on the utilization rate of 2174 ejaculates from June to August in 2016, a total of 166 Duroc boars were allocated into three groups: low utilization rate group (LG, 0 to 60% utilization rate), medium utilization rate group (MG, 60 to 80%), and high utilization rate group (HG, 80 to 100%). Serum and seminal plasma samples were collected, and element levels were analyzed using inductively coupled plasma mass spectrometry. The results showed that LG boars had higher concentrations of serum copper and seminal plasma cadmium compared with MG and HG boars (P < 0.05), and serum copper and seminal plasma cadmium were negatively correlated with sperm motility, while positively correlated with the abnormal sperm rate. We observed the abnormal sperm rate increased by approximately 4.53% with serum copper increasing from 1.63 to 2.44 mg/L, while sperm motility decreased by approximately 2.85% with seminal plasma cadmium increasing from 0 to 0.82 μg/L. Moreover, serum iron and manganese levels in the LG group were significantly reduced compared with the HG boars (P < 0.05), and the two elements were negatively correlated with the abnormal sperm rate (P < 0.05). In conclusion, excessive copper and absence of iron and manganese in serum as well as higher seminal plasma cadmium may reduce the utilization rate of semen by impairing sperm motility and morphology, indicating the importance of adding and monitoring microelements in boar diet.

Effects of oligomeric proanthocyanidins on quality of boar semen during liquid preservation at 17 °C

The use of antioxidants is an important aspect in the preservation of boar semen. Oligomeric proanthocyanidins (OPC) are an effective natural antioxidants that scavenges free radicals and reactive oxygen species (ROS). This study was designed to investigate the antioxidative effect of OPC on boar semen quality during liquid preservation at 17 °C. The effects of different concentrations of OPC on sperm quality variables, antioxidant effects and fertility were analyzed in this experiment. Semen collected from six Guanzhong-Black boars and was diluted with Beltsville thawing solution (BTS). During the process of liquid preservation at 17 °C, the variables assessed were measured and analyzed every 24 h. The addition of OPC improved boar sperm motility, acrosome integrity, membrane integrity, and mitochondrial membrane potential as compared with that of the control group (P <  0.05). Meanwhile, malondialdehyde content (MDA) and ROS content was less after adding OPC, thereby improving the total antioxidant capacity (T-AOC) (P <  0.05). Different concentrations of OPC have different degrees of protective effects on boar semen quality. The results indicate that 50 μg/mL of OPC was the optimum concentration, and that the conception rate, litter size, and survival rate increased at this concentration as compared with that of the control group (P <  0.05). In summary, the addition of OPC to BTS diluents can improve the quality of boar semen at 17 °C during liquid preservation. Further research is needed to understand the mechanism by which OPC provides protection to boar semen during preservation in vitro.

RNA sequencing reveals candidate genes and polymorphisms related to sperm DNA integrity in testis tissue from boars

Background

Sperm DNA is protected against fragmentation by a high degree of chromatin packaging. It has been demonstrated that proper chromatin packaging is important for boar fertility outcome. However, little is known about the molecular mechanisms underlying differences in sperm DNA fragmentation. Knowledge of sequence variation influencing this sperm parameter could be beneficial in selecting the best artificial insemination (AI) boars for commercial production. The aim of this study was to identify genes differentially expressed in testis tissue of Norwegian Landrace and Duroc boars, with high and low sperm DNA fragmentation index (DFI), using transcriptome sequencing.

Results

Altogether, 308 and 374 genes were found to display significant differences in expression level between high and low DFI in Landrace and Duroc boars, respectively. Of these genes, 71 were differentially expressed in both breeds. Gene ontology analysis revealed that significant terms in common for the two breeds included extracellular matrix, extracellular region and calcium ion binding. Moreover, different metabolic processes were enriched in Landrace and Duroc, whereas immune response terms were common in Landrace only. Variant detection identified putative polymorphisms in some of the differentially expressed genes. Validation showed that predicted high impact variants in RAMP2, GIMAP6 and three uncharacterized genes are particularly interesting for sperm DNA fragmentation in boars.

Conclusions

We identified differentially expressed genes between groups of boars with high and low sperm DFI, and functional annotation of these genes point towards important biochemical pathways. Moreover, variant detection identified putative polymorphisms in the differentially expressed genes. Our results provide valuable insights into the molecular network underlying DFI in pigs.

Electronic supplementary material

The online version of this article (10.1186/s12917-017-1279-x) contains supplementary material, which is available to authorized users.

A 4-year study of the proportional distribution of male reproductive organ abnormalities in cattle slaughtered at Nyagatare abattoir, Eastern Rwanda

Male reproductive performance has more impact on overall herd productivity than in the female. In order to assess herd productivity in cattle in Nyagatare, Eastern Rwanda, the proportional distribution of male reproductive organ abnormalities was investigated in 3087 bulls slaughtered over a 4‐year period. The aim of the study was to investigate the proportional distribution of male reproductive organ abnormalities in exotic and indigenous bulls slaughtered over a 4‐year period at Nyagatare abattoir in Eastern Rwanda. Positioning of the testicles was observed and recorded as the animals were assembled before slaughter. After slaughter, the internal and external reproductive organs of all bulls were removed, labelled and analysed for pathology. Significantly more indigenous (79.01%) than exotic (20.99%) animals were slaughtered (P < 0.05; N = 3 087). Overall occurrence of abnormalities was significantly higher in exotic (20.83%) than in indigenous (10.33%) animals (P < 0.05). Overall, abnormal location of testicles was the most common abnormality (4.08%) followed by abnormal prepuce and penis (2.33%), orchitis (1.94%), enlarged vesicular gland (0.91%), scrotal hernia (0.87%), unilateral cryptorchidism (0.81%), testicular hypoplasia (0.81%) and hydrocoele (0.78%). Abnormal location of testicles, abnormal prepuce and penis, orchitis, testicular hypoplasia and enlarged vesicular glands had significantly higher prevalence in exotic animals than in indigenous animals (P < 0.05). There was no significant difference in the prevalence of unilateral cryptorchidism, hydrocoele and scrotal hernia between the exotic and indigenous breeds. The encountered reproductive abnormalities result in poor herd fertility manifesting as low first‐service conception rates, prolonged breeding seasons and reduced weaning weights accompanied by inevitable financial losses in beef production. The observed high proportion of male reproductive abnormalities in exotic breeds might offset the professed benefits from introduction of these exotic breeds with the aim of improving productivity.

The influence of macro- and microelements in seminal plasma on diluted boar sperm quality

Background

Growing evidence indicates that macro- and microelements in the seminal plasma of humans and various domestic animals are of great importance due to their roles in sperm metabolism, function, survival and oxidative stress. In the present study, we therefore determined the concentrations of macro- and microelements in fresh boar seminal plasma and their relation to sperm quality parameters after 3 days of liquid storage was assessed. Twenty ejaculates from eight boars were collected, and semen volume, concentration, sperm motility, morphology, tail membrane integrity, plasma membrane permeability, mitochondrial membrane potential and DNA fragmentation were determined on the day of collection (day 0) and day 3 (72 h) of storage at 15–17 °C. Seminal plasma was separated and the concentrations of macroelements (Na, K, Ca, and Mg) and microelements (Cu, Fe, Zn and Se) were determined.

Results

After 3 days of storage Se levels correlated significantly with sperm motility, progressive motility and morphology, all of which are routinely used for semen evaluation. On day 3, Se levels also correlated with tail membrane integrity, viability and intact DNA (P < 0.05). The correlation coefficients showed that mitochondrial function was better preserved at higher levels of Zn, while higher levels of Cu decreased mitochondrial function, but led to the better preservation of DNA. It was also evident that higher levels of Fe were associated with higher proportions of live spermatozoa and of spermatozoa with normal morphology after 3 days of storage (P < 0.05), while higher levels of Ca and Mg in fresh seminal plasma were associated with lower percentages of progressive motile spermatozoa and with a decreased proportion of spermatozoa with intact DNA (P < 0.05). Multivariate analysis including microelements showed that Se significantly affected sperm quality parameters, mentioned above, after 3 days of storage.

Conclusions

Macro- and microelements were associated with boar sperm quality and may be important biomarkers of boar sperm quality after liquid storage. Our results demonstrate that the evaluation of Se in fresh boar seminal plasma can serve as an additional tool in predicting sperm quality after storage.

Revisiting summer infertility in the pig: could heat stress-induced sperm DNA damage negatively affect early embryo development?

Temperature is a crucial factor in mammalian spermatogenesis. The scrotum, pampiniform plexus, and cremaster and dartos muscles in mammals are specific adaptations to ensure sperm production in a regulated environment 4−6°C below internal body temperature. However, the limited endogenous antioxidant systems inherent in mammalian spermatozoa compounded by the loss of cytosolic repair mechanisms during spermatogenesis, make the DNA in these cells particularly vulnerable to oxidative damage. Boar sperm is likely to be more susceptible to the effects of heat stress and thus oxidative damage due to the relatively high unsaturated fatty acids in the plasma membrane, low antioxidant capacity in boar seminal plasma, and the boar’s non-pendulous scrotum. Heat stress has a significant negative impact on reproductive performance in piggeries, which manifests as summer infertility and results in productivity losses that amount to millions of dollars. This problem is particularly prevalent in tropical and subtropical regions where ambient temperatures rise beyond the animal’s zone of thermal comfort. Based on preliminary studies in the pig and other species, this article discusses whether heat stress could induce sufficient DNA damage in boar sperm to significantly contribute to the high rates of embryo loss and pregnancy failure observed in the sow during summer infertility. Heat stress-induced damage to sperm DNA can lead to disrupted expression of key developmental genes essential for the differentiation of early cell lineages, such as the trophectoderm, and can distort the timely formation of the blastocyst; resulting in a failure of implantation and ultimately pregnancy loss. Confirming such a link would prompt greater emphasis on boar management and strategies to mitigate summer infertility during periods of heat stress.

Towards microfluidic sperm refinement: impedance-based analysis and sorting of sperm cells

The use of high quality semen for artificial insemination in the livestock industry is essential for successful outcome. Insemination using semen with a high number of sperm cells containing morphological defects has a negative impact on fertilization outcome. Therefore, semen with a high number of these abnormal cells is discarded in order to maintain high fertilization potential, resulting in the loss of a large number of morphologically normal sperm cells (up to 70-80% of original sample). A commonly occurring morphological sperm anomaly is the cytoplasmic droplet on the sperm flagella. Currently, no techniques are available to extract morphologically normal sperm cells from rejected samples. Therefore, we aim to develop a microfluidic setup which is able to detect and sort morphologically normal sperm cells label-free and non-invasively. In a proof-of-concept experiment, differential impedance measurements were used to detect the presence of cytoplasmic droplets on sperm flagella, which was quantified by calculating the area under the curve (AUC) of the corresponding impedance peaks. A receiver operating characteristic curve of this electrical analysis method showed the good predictive power of this analysis method (AUC value of 0.85). Furthermore, we developed a label-free cell sorting system using LabVIEW, which is capable of sorting sperm cells based on impedance. In a proof-of-concept experiment, sperm cells and 3 μm beads were sorted label-free and non-invasively using impedance detection and dielectrophoresis sorting. These experiments present our first attempt to perform sperm refinement using microfluidic technology.

A comparative study of boar semen extenders with different proposed preservation times and their effect on semen quality and fertility

The present study compared the quality characteristics of boar semen diluted with three extenders of different proposed preservation times (short-term, medium-term and long-term). A part of extended semen was used for artificial insemination on the farm (30 sows/extender), while the remaining part was stored for three days (16–18 °C). Stored and used semen was also laboratory assessed at insemination time, on days 1 and 2 after the collection (day 0). The long-term extender was used for a short time, within 2 days from semen collection, with the aim to investigate a possible advantage over the others regarding laboratory or farm fertility indicators at the beginning of the preservation time. Viability, motility, kinetic indicators, morphology and DNA fragmentation were estimated. The results showed reduced viability, higher values for most of the kinetics, and higher immotile spermatozoa from day 1 to day 2 in all extenders; however, the long-term extender was superior compared to the other two on both days. With regard to morphology and chromatin integrity, the percentage of abnormal and fragmented spermatozoa increased on day 2 compared to day 1 for all of the extenders. However, based on the farrowing rate and the number of piglets born alive after the application of conventional artificial insemination within 2 days from semen collection/dilution, it was found that the medium-term diluents were more effective. In conclusion, it seems that the in vivo fertilization process involves more factors than simply the quality of laboratory evaluated sperm indicators, warranting further research.

Influence of boar breeds or hybrid genetic composition on semen quality and seminal plasma biochemical variables

The enzyme concentrations of seminal plasma are important for spermatozoa metabolism and function in boars. The need has arisen for introducing a biochemical evaluation of semen, along with the usual standard semen analyses. There are no data on the influence of boar breeds on the seminal plasma biochemical variables investigated in this study. Therefore, the objective was to determine the influence of breed and hybrid genetic composition of boars on semen quality and seminal plasma biochemical variables. Semen samples of 27 boars (Swedish Landrace, German Landrace, Large White, Pietrain and Pig Improvement Company hybrid-PIC-hybrid), aged between 1.5 and 3 years, were collected. After evaluation of semen quality, the seminal plasma was separated from the spermatozoa by centrifugation of semen. The seminal plasma was subjected to spectrophotometric analysis to determine alkaline phosphatase (ALP), acid phosphatase (ACP), γ-glutamyltransferase (GGT), creatine kinase (CK) and lactate dehydrogenase (LDH) and to atomic absorption spectrophotometric analysis to measure the concentration of calcium and magnesium. Conventional semen quality variables differed depending on breed and PIC-hybrid genetic composition, though these differences were typically insignificant. In the seminal plasma, significant differences were determined in enzyme activity (ALP, GGT, CK and LDH) and in calcium concentration among boars of different breeds. There are, therefore, differences in semen quality and significant differences in the seminal plasma biochemical variables among boars of different breeds and PIC-hybrid genetic composition. The data and differences in semen variables detected in the present study provide knowledge for enhancing evaluation and monitoring of boar reproductive potential, semen quality and explain the potential causes of boar infertility.

Mares prefer the voices of highly fertile stallions

We investigated the possibility that stallion whinnies, known to encode caller size, also encoded information about caller arousal and fertility, and the reactions of mares in relation to type of voice. Voice acoustic features are correlated with arousal and reproduction success, the lower-pitched the stallion's voice, the slower his heart beat and the higher his fertility. Females from three study groups preferred playbacks of low-pitched voices. Hence, females are attracted by frequencies encoding for large male size, calmness and high fertility. More work is needed to explore the relative importance of morpho-physiological features. Assortative mating may be involved as large females preferred voices of larger stallions. Our study contributes to basic and applied ongoing research on mammal reproduction, and questions the mechanisms used by females to detect males' fertility.

Semen effects on insemination outcomes in sows

Sows (n=1205) were artificially inseminated with semen from single sires (n=166). Semen was previously analysed for sperm concentration, motility, velocity, morphology (using DIC microscopy) and membrane integrity, sperm clump score, temperature on arrival and pH. Percent normal sperm influenced both numbers of pigs born alive (P<0.01) and litter size (P<0.05) which, in turn, was also influenced by abnormal sperm head morphology (P<0.05) and retained distal cytoplasmic droplets (P<0.01). Percent stillbirths were influenced by sperm flagellar beat cross frequency (P<0.05) and semen arrival temperature (P<0.05).

Changeability of sperm chromatin structure during liquid storage of ovine semen in milk-egg yolk- and soybean lecithin-based extenders and their relationships to field-fertility

The aim of this experiment was to study the effect of semen extender on sperm chromatin structure and to correlate chromatin integrity with field-fertility of preserved ram semen. Ejaculates of at least 2 × 10(9) sperm/ml and 70 % progressive motility were collected using an artificial vagina from Chios rams (n = 11, 4-6 years old), split-diluted to 1 × 10(9) sperm/ml with milk-egg yolk- and soybean lecithin (Ovixcell®)-based extenders, packaged in 0.5-ml straws and examined after 6, 24 and 48 h of storage at 5 ± 1 °C. Evaluation endpoints were computer-assisted sperm motion analysis, fluorescence-based analysis of chromatin structure by chromomycin A3 and acridine orange assays, and 65-day pregnancy rate (PR) of 34- to 36-h preserved semen after intra-cervical insemination of ewes (n = 154) in progestagen-synchronized estrus. Neither extender nor storage time had any influence on incidence of decondensed chromatin. Unlike Ovixcell® extender, deterioration of sperm motility (P < 0.01) and chromatin stability (P < 0.005) was detected after 48 h of storage in milk-egg yolk extender. Sperm motility accounted for 14.4-18.5 % of variations in chromatin integrity (P < 0.001). No significant difference was found in PR of Ovixcell®- and milk-egg yolk-stored semen. Nevertheless, PR differed between rams (14.3-71.4 %; P < 0.025). Chromatin integrity explained 10.2-56.3 % of variations in PR (P < 0.05-0.01). A pronounced decline in PR (19.1 %) was observed when percentages of decondensed and destabilized chromatin have reached thresholds of 10.5-30 % and 4-9 %, respectively. In conclusion, Ovixcell® is superior to milk-egg yolk extender in preserving chromatin stability and motility. Chromatin defects are negatively associated with sperm fertility.

Multivariate analyses for determining the association of field porcine fertility with sperm motion traits analysed by computer-assisted semen analysis and with sperm morphology

This study investigates the association of semen traits with boar fertility. The fertility outcome (farrowing rate - FR and total piglets born - TB) of 14 boars was obtained from a field trial conducted during 10 week of breeding period on a commercial farm using multiparous sows (n = 948) through single-sire mating with 2 × 10(9) motile sperm cells per artificial insemination (AI) dose. Sperm motion parameters, evaluated with computer-assisted semen analysis system in raw and stored semen at 17°C for 240 h, in addition to morphological sperm defects, measured on the collection day, were included in the analysis to determine which semen traits were important to discriminate the fertility potential of ejaculates from these boars. The data underwent multivariate cluster, canonical and discriminant analyses. Four clusters of boars were formed based on fertility outcome. One boar, with the lowest FR and TB values (89.7% and 11.98), and two boars, with the highest FR and TB values (97.8% and 14.16), were placed in different clusters. The other boars were separated in two distinct clusters (four and seven boars), including boars with intermediate TB (12.64 and 13.22) but divergent values for FR (95.9% vs 91.8%). Semen traits with higher discriminatory power included total motility, progressive motility, amplitude of lateral head displacement and cytoplasmatic droplets. Through multivariate discriminant analysis, more than 80% of the 140 ejaculates were correctly classified into their own group, showing that this analysis may be an efficient statistical tool to improve the discrimination of potential fertility of boars. Nevertheless, the validation of the relationship between fertility and semen traits using this statistical approach needs to be performed on a larger number of farms and with a greater number of boars.

Reduced glutathione and procaine hydrochloride protect the nucleoprotein structure of boar spermatozoa during freeze–thawing by stabilising disulfide bonds

One important change the head of boar spermatozoa during freeze–thawing is the destabilisation of its nucleoprotein structure due to a disruption of disulfide bonds. With the aim of better understanding these changes in frozen–thawed spermatozoa, two agents, namely reduced glutathione (GSH) and procaine hydrochloride (ProHCl), were added at different concentrations to the freezing media at different concentrations and combinations over the range 1–2 mM. Then, 30 and 240 min after thawing, cysteine-free residue levels of boar sperm nucleoproteins, DNA fragmentation and other sperm functional parameters were evaluated. Both GSH and ProHCl, at final concentrations of 2 mM, induced a significant (P < 0.05) increase in the number of non-disrupted sperm head disulfide bonds 30 and 240 min after thawing compared with the frozen–thawed control. This effect was accompanied by a significant (P < 0.05) decrease in DNA fragmentation 240 min after thawing. Concomitantly, 1 and 2 mM GSH, but not ProHCl at any of the concentrations tested, partially counteracted the detrimental effects caused by freeze–thawing on sperm peroxide levels, motility patterns and plasma membrane integrity. In conclusion, the results show that both GSH and ProHCl have a stabilising effect on the nucleoprotein structure of frozen–thawed spermatozoa, although only GSH exerts an appreciable effect on sperm viability.

Boar seminal plasma components and their relation with semen quality

Select boar seminal plasma (SP) components and their relation to semen quality were investigated. Thirty nine boars from three artificial insemination (AI) centers were divided into group A (GA: > 80% normal sperm and >70% motility) and group B (GB: < 80% normal sperm and < 70% motility). Each ejaculate was collected and semen volume, concentration, sperm motility (computer aided semen analysis; CASA), morphology, and vitality (both eosin nigrosin staining) were investigated. The SP was separated and analyzed for aspartate-amino-transferase (AST), γ-glutamyl-transferase (GGT), alkaline phosphatase (ALP) activity, and the concentrations of sodium (Na), potassium (K), chloride (Cl), calcium (Ca), phosphate (PO(4)(3-)), magnesium (Mg), selenium (Se) and zinc (Zn) were assessed. Repeated measures (2 months interval) were conducted in eight boars of GA from one AI center. The activity of GGT (r = -0.482) and ALP (r = -0.459) was moderately associated (p < 0.05) with ejaculate volume and strongly associated with concentration (r = 0.580 and r = 0.618, respectively; p = 0.000). Moderate associations (p < 0.05) were found between ALP (r = 0.439), GGT (r = 0.387), Na (r = -0.428), K (r = 0.354), and Se (r = 0.354) with progressive motility. The SP concentration of Na (r = -0.401), Cl (r = -0.521), and K (r = 0.350) was associated (p < 0.05) with normal morphology. Only Mg was associated (p < 0.05) with membrane damage (r = -0.335). The concentration of Na, Cl, and Zn (1681.0 vs. 1701.0 µg/dL) was different between groups (p < 0.05). Repeated measures showed significant differences in time but only for Na, Mg, and Zn (p < 0.05). In conclusion, several biochemical components of SP were related to semen quality. The analysis of biochemical parameters could provide extra information about reproductive health of AI boars.

Automated sperm head morphology analyzer for open-source software

Sperm head morphology has been identified as a characteristic that can be used to predict a male's semen quality. In the present study, we have developed an automated sperm head morphology analysis (ASMA) plug-in for open-source ImageJ software (http://rsbweb.nih.gov/ij/). We describe the plug-in's functionality, and confirm its validity for sperm head morphology analysis using fish sperm. Sperm head morphological measurements (length and width) made with the ASMA plug-in did not differ from manual measurements. Using the plug-in to measure sperm head-shaped objects of known size, the associated plug-in error rate was < 0.5%. Brightness and contrast ratios influenced sperm head measurements, suggesting the need for standardized protocols. This plug-in was effective at measuring elliptical (i.e., Atlantic cod) as well as slightly irregular (i.e., Chinook salmon) shaped sperm heads. In conclusion, our ASMA plug-in represents a versatile alternative to costly sperm morphology software.