The Predictive Value of Porcine Seminal Parameters on Fertility Outcome under Commercial Conditions

Artificial insemination and optimization of the use of seminal doses in swine

The optimization of processes associated with artificial insemination (AI) is of great importance for the success of the pig industry. Over the last two decades, great reproductive performance has been achieved, making further significant progress limited. Optimizing the AI program, however, is essential to the pig industry's sustainability. Thus, the aim is not only to reduce the number of sperm cells used per estrous sow but also to improve some practical management in sow farms and boar studs to transform the high reproductive performance to a more efficient program. As productivity is mainly influenced by the number of inseminated sows, guaranteeing a constant breeding group and with healthy animals is paramount. In the AI studs, all management must ensure conditions to the health of the boars. Some strategies have been proposed and discussed to achieve these targets. A constant flow of high-quality and well-managed breeding groups, quality control of semen doses produced, more reliable technology in the laboratory routine, removal of less fertile boars, the use of intrauterine AI, the use of a single AI with control of estrus and ovulation (fixed-time AI), estrus detection based on artificial intelligence technologies, and optimization regarding the use of semen doses from high genetic-indexed boars are some strategies in which improvement is sought. In addition to these new approaches, we must revisit the processes used in boar studs, semen delivery network, and sow farm management for a more efficient AI program. This review discusses the challenges and opportunities in adopting some technologies to achieve satisfactory reproductive performance and efficiency.

Comparative developmental competence of in vitro embryos recovered from Bali cattle with normal and poor sperm motility

Background and Aim

Fertility is crucial for enhancing the efficiency of livestock production, as it directly impacts the reproductive rates. A comprehensive understanding of the relationship between sperm quality and embryo development is key to optimizing reproductive outcomes and improving the quality of livestock. This study analyzed the developmental competence of in vitro embryos recovered from Bali cattle with normal or poor sperm motility.

Materials and Methods

Nine bulls with normal fresh semen (NFS) or poor fresh semen (PFS) motility were ejaculated for semen. Semen ejaculates, including volume, motility, and sperm concentration, were evaluated immediately after collection to measure the quality of the fresh semen. Frozen semen was evaluated using computer-assisted semen analysis (CASA) for motility, progressive sperm motility, distance curve path, distance curve linear, distance straight line, average path velocity, curvilinear velocity, linear velocity, straightness (STR), linearity of forward progression (LIN), wobble, and average lateral head displacement (ALH). Bull groups were used to determine in vitro embryo cleavage ability after fertilization of Bali cattle. Ovaries of Bali cattle were collected by slicing, and only cytoplasmic oocytes with compact cumulus cells were used in this study. The oocytes were matured, and in vitro fertilization was performed using fertilization media with a final sperm concentration of 1.5 × 106 spermatozoa/mL. After 48 h, the embryo cleavage ability of the cultured oocytes was evaluated.

Results

There were significant differences in motility values between the NFS and PFS groups; however, there were no significant differences in the volume or sperm concentration. There was a significant difference in the LIN value between the groups but no significant differences in other CASA parameters. There were no significant differences in the cleavage rate and morula between the groups, but a positive correlation was observed between the cleavage rate and the morula and between the morula and ALH. A significant negative correlation was observed between the cleavage rate and STR and between the morula and STR; no significant differences were observed for other variables.

Conclusion

Despite variations in sperm characteristics, both normal and poor sperm motility demonstrated comparable in vitro embryonic development competence. These findings provide important insights into the fertility potential of Bali bulls, providing valuable information that can enhance selection strategies to improve the quality of livestock production.

Ovine fertility by artificial insemination in the breeding season could be affected by intraseasonal variations in ram sperm proteomic profile

It is important to note that seasonality could affect ram reproductive parameters, and therefore, fertility results after artificial insemination. In this work, 1) we assessed fertility rates after cervical artificial insemination of 11,805 ewes at the beginning (June 21st to July 20th) and at the end (November 20th to December 21st) of the reproductive season in the Assaf breed for the last four years, and 2) we aimed to identify male factors influencing the different reproductive success obtained depending on the time at the mating season in which ovine artificial insemination was performed. For this purpose, we evaluated certain ram reproductive and ultrasonographical parameters as well as we performed a multiparametric and proteomic sperm analysis of 6-19 rams at two very distant points in the mating season (July as Early Breeding Season -EBS- and November as Late Breeding Season -LBS-). Rutinary assessments carried out in the ovine reproduction centers (testicular volume, libido, sperm production and mass motility) showed non-significant differences (P ≥ 0.05) between both studied times, as well as the ram ultrasonographic evaluation (Resistive and Pulsatility Index as Doppler parameters; and pixels mean gray level, and hypoechoic areas percentage and density as echotexture parameters). However, at level of sperm functionality, although sperm quality appeared non-significantly lower (P ≥ 0.05) in the EBS, we identified a significantly different (P < 0.05) sperm proteomic profile between the seasonality points. The following proteins were identified with the lowest abundance in the EBS with a fold change > 4, a P = 2.40e-07, and a q = 2.23e-06: Fibrous Sheath-Interacting Protein 2, Disintegrin and Metalloproteinase Domain-Containing Protein 20-like, Phosphoinositide-Specific Phospholipase C, Tektin 5, Armadillo Repeat-Containing Protein 12 Isoform X3, Solute Carrier Family 9B1, Radial Spoke Head Protein 3 Homolog, Pro-Interleukin-16, NADH Dehydrogenase [Ubiquinone] 1 Alpha Subcomplex Subunit 8, Testis, Prostate and Placenta-Expressed Protein, and Acyl Carrier Protein Mitochondrial. In conclusion, while our basic analyses on male and sperm quality showed similar results between the beginning and the end of the breeding season, on a proteomic level we detected a lower expression of sperm proteins linked to the energy metabolism, sperm-oocyte interactions, and flagellum structure in the EBS. Probably, this different protein expression could be related to the lower fertility rate of Assaf ewes after cervical artificial insemination at this time. More importantly, sperm proteins can be used as highly effective molecular markers in predicting sperm fertilization ability related to intraseasonal variations.

Update on artificial insemination: Semen, techniques, and sow fertility

Over the years, reproductive efficiency in the swine industry has focused on reducing the sperm cell number required per sow. Recent advances have included the identification of subfertile boars, new studies in extended semen quality control, new catheters and cannulas for intrauterine artificial insemination (AI), and fixed-time AI under commercial use. Therefore, it is essential to link field demands with scientific studies. In this review, we intend to discuss the current status of porcine AI, pointing out challenges and opportunities to improve reproductive efficiency.

Are There Differences between Methods Used for the Objective Estimation of Boar Sperm Concentration and Motility?

Artificial insemination in the swine industry, as in other species, demands adequate semen handling and accurate evaluation for the preparation of seminal doses. Sperm concentration and motility estimates are part of the semen evaluation process and are considered important for maximizing the yield of doses for insemination. In this study, methods were examined for their accuracy in the estimation of boar sperm concentration and motility. Assessments of sperm concentration were carried out using iSperm^®, ISAS^® v1, Open CASA v2, and the Accuread^® photometer. Analyses of sperm motility were performed with iSperm^®, ISAS^® v1, and Open CASA v2 systems. In this study, boar semen samples were collected from 10 healthy males from two genetic lines. There were no relevant differences between sire lines when sperm concentration was assessed. A Bayesian analysis was applied to the four methods used to assess sperm concentration to examine whether there are relevant differences between them. Results suggested differences in the four methods, with a probability of relevance (PR) of 0.86-1.00. The iSperm^® method revealed higher concentration values within the highest posterior density region at 95% confidence interval (HPD_95%) = 167.0, 224.2 M/mL, whereas Open CASA v2 showed the lowest values, with HPD_95% = 99.3, 155.9 M/mL. The iSperm^® demonstrated higher reliability in measuring sperm concentration compared to other methods or devices within the given range of confidence. ANOVAs revealed relevant differences in the three methods of motility estimation. Overall, differences in boar sperm concentration and motility estimates were found using various methods, but further studies are needed for better characterization of these differences.

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.

Compensability of an enhanced incidence of spermatozoa with cytoplasmic droplets in boar semen for use in artificial insemination: a single cell approach

This single cell study aimed to clarify whether an elevated incidence of sperm with a retained cytoplasmic droplet (CD) can be compensated by a higher sperm number in boar semen doses to maintain fertility. Cluster analysis of motile spermatozoa (ten boars) revealed that spermatozoa with a CD are underrepresented in the fast, linearly moving sperm cohort compared to morphologically normal sperm. Nonetheless, the response to the motility stimulator procaine was barely affected in spermatozoa with distal CD (Cramer's V = 0.14), but moderately affected in sperm with proximal CD (V = 0.28). Viability was lower in sperm with distal CD (p < 0.05) but not with proximal CD compared to normal sperm during 168 h storage of extended semen samples (n = 11) and subsequent thermic stress. Morphologically normal sperm from normospermic samples (n = 10) or samples with a high incidence (≥ 15%) of sperm with CD (n = 9) had similar motility patterns and responses to procaine. The origin of morphologically normal sperm had no effect on sperm viability (p > 0.05; n = 26). In conclusion, a moderately enhanced prevalence of sperm with CD seems to be compensable by an increase in sperm numbers in boar semen doses.

Compensability of Enhanced Cytoplasmic Droplet Rates in Boar Semen: Insights of a Retrospective Field Study

Retained cytoplasmic droplets (CD) provide the most abundant sperm abnormality in boar and reduce fertility. It is still unclear as to whether high CD rates in semen portions are compensable. The aim was to explore the impact of CD in relation to quantitative and qualitative sperm traits on fertility performance of sows. Retrospective data analysis of 1497 inseminations was performed. Ejaculates (n = 260) were assigned to three groups with low (<10%), medium (≥10% to <15%), and high (≥15%) CD rates. Average sperm numbers were lowest in the high CD group (2.08 × 109/mL). Membrane integrity and mitochondrial activity did not differ between the groups. Breakpoint analysis indicated a shift towards lower litter sizes when the CD rate exceeded 11%. Group comparisons revealed no difference in litter size (p = 0.205), together with a slightly higher farrowing rate in the high CD group (p < 0.001), which coincided with higher resistance against temperature stress in the stored semen samples (p < 0.001) and a higher sperm motility (p < 0.001). In conclusion, an increased prevalence of CD in boar semen is compensable by high tolerance against temperature stress, whereas sperm numbers per dose are less relevant.

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.

Testis-Specific Isoform of Na+-K+ ATPase and Regulation of Bull Fertility

An advanced understanding of sperm function is relevant for evidence-based male fertility prediction and addressing male infertility. A standard breeding soundness evaluation (BSE) merely identifies gross abnormalities in bulls, whereas selection based on single nucleotide polymorphisms and genomic estimated breeding values overlooks sub-microscopic differences in sperm. Molecular tools are important for validating genomic selection and advancing knowledge on the regulation of male fertility at an interdisciplinary level. Therefore, research in this field is now focused on developing a combination of in vitro sperm function tests and identifying biomarkers such as sperm proteins with critical roles in fertility. The Na⁺-K⁺ ATPase is a ubiquitous transmembrane protein and its α4 isoform (ATP1A4) is exclusively expressed in germ cells and sperm. Furthermore, ATP1A4 is essential for male fertility, as it interacts with signaling molecules in both raft and non-raft fractions of the sperm plasma membrane to regulate capacitation-associated signaling, hyperactivation, sperm-oocyte interactions, and activation. Interestingly, ATP1A4 activity and expression increase during capacitation, challenging the widely accepted dogma of sperm translational quiescence. This review discusses the literature on the role of ATP1A4 during capacitation and fertilization events and its prospective use in improving male fertility prediction.

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.

The TUNEL assay underestimates the incidence of DNA damage in pig sperm due to chromatin condensation

Inconsistencies in the relationship between sperm DNA fragmentation and reproductive outcomes as well as the low incidence in farm animals raise concerns on its actual value as a sperm quality parameter. Previous studies suggested that the different sensitivity of techniques evaluating DNA fragmentation could explain variations in the correlation with reproductive outcomes. While the TUNEL assay is one of the most standardized methods to detect DNA damage and cell death, the steric impediment for the terminal nucleotidyl transferase enzyme to access the highly condensed sperm nucleus may decrease the ability of this test to detect internal DNA breaks. In the present study, we sought to determine whether increasing chromatin decondensation makes the TUNEL assay more sensitive to detect DNA damage in pig sperm. We compared three chromatin decondensation treatments (2 mM DTT for 45 min; 5 mM DTT for 8 min and further 45 min; and 5 mM DTT+ 1 M NaCl for 8 min) through the Chromomycin A3 test (CMA3). While incubation with DTT increased the percentages of sperm with decondensed chromatin, regardless of concentration and time of incubation (P < 0.05), the extent of that decondensation was higher when 5 mM DTT was combined with 1 M NaCl. In addition, the TUNEL assay detected a higher number of DNA breaks in sperm with decondensed chromatin (1.89% ± 1.63% vs 8.74% ± 6.05%; P = 0.003). This study shows, for the first time, that previous chromatin decondensation increases the sensitivity of the TUNEL assay to detect DNA damage in pig sperm. These findings also support that larger chromatin decondensation is needed in order for DNA damage to be evaluated properly in species containing protamine P1 only.

Suitability of semen stress tests for predicting fertilizing capacity of boar ejaculates

Besides classical semen parameters, semen stress tests (SSTs) are helpful tools to assess the fertilizing capacity of sperm. However, valid studies on SSTs in relation to fertility are rare because several corrections of common fertility parameters for female and male effects are required. Therefore, over a one-year period, we analyzed semen parameters of 260 ejaculates obtained from 130 Pietrain boars aged between 8 and 9 months in one AI center as well as 1521 corresponding insemination records for these ejaculates. Two consecutive ejaculates (4th and 5th) were collected from each boar and extended in DiluPorc™ BTS. In addition to routine semen evaluation, sperm motility was assessed after heat-resistance test (300 min incubation at 38 °C after seven days storage at 16 °C, HRT) and cold-resistance test (10 min incubation at 38 °C after three days storage at 6 °C, CRT). Generalized linear models (GLMs) were applied to analyze effects for the following predictors of farrowing rate (FR), number of total born (NTB) and live born (NLB) piglets: farm (P = 0.013 [FR], P = 0.001 [NTB], P = 0.023 [NLB]), parity (P = 0.679, P = 0.01, P < 0.001), weekday (P = 0.012, P = 0.08, P = 0.009) and year × season (P < 0.001, P = 0.688, P = 0.574). On boar level, GLMs revealed significant effects on FR, NTB and NLB for the predictors sow (all P < 0.001), total sperm number per dose (P = 0.007, P = 0.002, P < 0.001), total sperm motility (P = 0.002, P = 0.2, P = 0.003) and mitochondrial activity (P = 0.004, P < 0.001, P = 0.002). Moreover, FR and NTB were influenced by membrane integrity (both P < 0.001), FR and NLB by cold-resistance (P < 0.001, P = 0.043), and NTB and NLB by sperm morphology (P = 0.001, P < 0.001) and boar (both P < 0.001). NLB was additionally influenced by heat-resistance (P = 0.004) and farm (P = 0.018) and solely NTB was influenced by sperm output (P = 0.03). Boar and semen related factors explained 9% of the total variation in NTB and 7% of the total variation in NLB. Only 14.2% (n = 37) of the samples were both cold- and heat-resistant (≥65% of motile sperm). Cold- and heat-resistance were dependent factors (Chi-square, P = 0.001) and sperm motility after CRT and HRT showed a moderate positive correlation (r_s = 0.40, P < 0.001, Spearman's rho). Finally, ROC curves demonstrated that neither SST can be used as a sole test for predicting the fertilizing capacity of boar ejaculates.

A High Incidence of Sperm with Cytoplasmic Droplets Affects the Response to Bicarbonate in Preserved Boar Semen

Retained cytoplasmic droplets (CD) are the most frequent sperm abnormality in boar semen. A high incidence of CD is associated with subfertility, but the underlaying reasons are not well understood. The storage of extended semen might augment the adverse effects of CD on essential steps towards fertilization, such as capacitation. The aim of this study was to examine whether the enhanced presence of CD in boar semen influences sperm's response to the capacitation stimulus bicarbonate during long-term semen storage. Extended semen samples (n = 78) from 13 artificial insemination centers were analyzed using a flow cytometric calcium influx assay. Samples with >15% of CD showed a reduced specific response to bicarbonate and a higher non-specific destabilization after storage for 96 h and subsequent incubation at 38 °C in three variants of Tyrode's medium (p < 0.05). The size of the bicarbonate-responsive sperm population was inversely correlated with the presence of CD-bearing sperm (r = -0.61, p < 0.01). Samples with ≤15% and samples with >15% of CD did not differ in motility or viability and acrosome integrity during semen storage. In conclusion, incomplete epididymal sperm maturation impairs the in vitro capacitation ability and promotes sperm destabilization in stored boar semen.

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.

Photo Stimulation of Seminal Doses with Red LED Light from Duroc Boars and Resultant Fertility in Iberian Sows

Simple Summary

The main objective of breeding Iberian pigs is the production of high-quality dry cured meat products. As this breed shows a reduced litter size in comparison to the commercial breeds, some previous studies have reported the use of photostimulation of seminal doses as a method for improving the farrowing rate and litter size. The aim of this study was to explore whether the application of a photostimulation procedure to Duroc seminal doses has any beneficial effect on fertility and litter size. Semen samples were obtained from 38 fertile Duroc boars and the fertility study was conducted on two commercial farms using multiparous Iberian sows (farm A, n = 824; farm B, n = 2131), that were randomly assigned to LED (L) or control (C) groups. Post-cervical insemination took place 0 and 24 h after the diagnosis of estrus, with seminal doses from the same ejaculate and same treatment. The photostimulation of the seminal doses had no effect on the reproductive performance (farrowing rate: 91.72% C vs. 90.09% L, litter size: 8.71 ± 0.06 piglets C vs. 8.70 ± 0.05 L, p > 0.05).

Abstract

In pigs, it has been reported that increased farrowing rates and litter size have been induced by photostimulating the seminal doses for artificial insemination with red LED light. As the reproductive characteristics, production system, and outcome parameters of Iberian breed pigs are different from other commercial breeds, the aim of this study was to evaluate the possible effect of illuminating seminal doses from Duroc boars with red LED light and the fertility outcomes of Iberian females. Semen samples were obtained from 38 fertile Duroc boars. Photostimulation of the artificial insemination (AI) seminal doses was carried out by illuminating the samples with a red LED for 10 min, followed by 10 min of darkness, and finally 10 additional minutes of red light. The fertility study was conducted on two commercial farms using multiparous Iberian sows (farm A, n = 824; farm B, n = 2131), that were randomly assigned to LED (L) or control (C) groups. No differences were found between L and C groups in both farms (p > 0.05) for parity, pregnancy rate, duration of pregnancy, farrowing rate, and litter size (total, alive, and stillborn piglets). Farrowing rates in farm A were 88.8% (n = 383) for control and 89.6% (n = 441, p = 0.67) for the LED group. In farm B, farrowing rates were C:90.5% (n = 1030) and L: 90.1% (n = 1101, p = 0.48). In farm A, total born piglets were 8.69 ± 0.11 for C and 8.71 ± 0.11 for L (p = 0.87). In farm B, the results were 8.72 ± 0.7 for C and 8.70 ± 0.06 (p = 0.82) for L. Under the production conditions for the Iberian breed, the photostimulation with red LED light using Duroc pig seminal doses was not effective in improving the fertility of Iberian sows.

Influence of Non-conventional Sperm Quality Parameters on Field Fertility in Ovine

The prediction of the fertilizing ability of a seminal dose continues to be a primary aim in the field of artificial insemination (AI). To achieve this goal, in this study we have included the evaluation of some non-conventional sperm quality markers. A total of 3,906 ewes from 52 different farms were inseminated with 357 refrigerated seminal doses obtained from 45 mature Rasa Aragonesa rams. The same samples were used for sperm quality analysis including membrane integrity, capacitation status, oxygen consumption and apoptotic-like markers such as phosphatidylserine translocation (PS), plasmalemma disorganization/mitochondrial membrane potential, caspase activation and DNA damage. Seminal doses from the breeding (B) season presented higher percentages of intact membrane (IM), non permeant (NP) membrane with high mitochondrial membrane potential (ΔΨm) and IM without PS translocation spermatozoa than those from the non-breeding (NB) season. Therefore, we can conclude that there were less spermatozoa showing apoptotic-like features in the seminal doses from the B than the NB season, although these differences did not affect field fertility. Only the percentage of intact membrane, non-capacitated (IM-NC) spermatozoa showed a significant correlation with in vivo fertility (P = 0.005) and fecundity (P = 0.007) values obtained after cervical AI when all data were evaluated. When the data were sorted by season and distance to the farms where AI was performed, the correlation between the percentage of IM-NC spermatozoa and reproductive parameters increased in the NB season and progressively with remoteness from the farms. Some other sperm parameters, like NP with high ΔΨm, IM sperm without active caspases and DNA-intact spermatozoa, also showed significant correlations with the reproductive parameters in the sorted data. Moreover, the increment in both the percentage of IM-NC and DNA-intact spermatozoa would increase the probability of obtaining a fertility higher than the mean (>52%), as revealed by a multiple logistic regression analysis. In conclusion, we have identified two seminal markers—the percentage of intact membrane, non-capacitated spermatozoa, and DNA intact spermatozoa—which could be used as a test to discard males in AI programs, which is highly important from an economic point of view and can contribute to achieving satisfactory fertility rates.

Evaluation of α5β1 integrin as a candidate marker for fertility in bull sperm samples

With the progressive increase in the use of reproductive biotechnologies in the cattle industry, like artificial insemination and in vitro embryo production, the accurate determination of fertilizing competence of cryopreserved sperm samples is an essential issue. The routine methodology to assess bull sperm quality relies primarily on count, viability and motility of spermatozoa. However, these parameters do not tightly predict the reproductive success of samples. Therefore, identification of complementary markers of sperm functionality to strengthen the predictability of traditional spermogram is desirable to improve livestock reproduction practices. Previous results from our laboratory indicated that α5β1 integrin plays a key role in bovine sperm function and mediates their interaction with the female reproductive tract. Thus, this study aimed to investigate whether the localization of α5β1 held a correlation with fertilizing ability of bovine cryopreserved semen samples. Firstly, we assessed the quality of samples from six different bulls (A-F). We determined motility and viability of sperm samples after thawing and selection. Additionally, we measured the capacitation state of the samples by chlortetracycline (CTC) assay in the presence or absence of heparin, as an indicator of their responsiveness to a capacitating stimulus. Based on these assays, samples were classified being A the bull with the lowest quality and F the bull with the highest quality. Then, we studied the presence and localization of α5β1 integrin. This protein showed a distribution pattern in the acrosomal (A), post-acrosomal (P) and acrosomal + post-acrosomal (A + P) regions with different localization percentages among the studied samples. Next, we determined the fertilizing ability of the samples in in vitro fertilization (IVF) assays and performed correlation analyses between IVF outcome and the routine spermogram parameters or α5β1 integrin localization patterns. When the percentage of cells showing α5β1 integrin was compared to fertilization rate, no correlation was observed. However, the presence of α5β1 integrin in P and A + P regions (PA pattern), positively correlated with IVF rate (p < 0.05). These results suggest that while routine semen analyses failed to predict sperm reproductive competence, integrin localization in post-acrosomal region (PA pattern) showed a positive correlation with IVF outcome, thus posing an attractive marker to predict more accurately the reproductive performance of an individual.

Integration of whole-genome DNA methylation data with RNA sequencing data to identify markers for bull fertility

Predicting bull fertility prior to breeding is a current challenge for the dairy industry. The use of molecular biomarkers has been previously assessed. However, the integration of this information has not been performed to extract biologically relevant markers. The goal of this study was to integrate DNA methylation data with previously published RNA-sequencing results in order to identify candidate markers for sire fertility. A total of 1765 differentially methylated cytosines were found between high- and low-fertility sires. Ten genes associated with 11 differentially methylated cytosines were found in a previous study of gene expression between high- and low-fertility sires. Additionally, two of these genes code for proteins found exclusively in bull seminal plasma. Collectively, our results reveal 10 genes that could be used in the future as a panel for predicting bull fertility.

Gene Polymorphisms in Boar Spermatozoa and Their Associations with Post-Thaw Semen Quality

Genetic markers have been used to assess the freezability of semen. With the advancement in molecular genetic techniques, it is possible to assess the relationships between sperm functions and gene polymorphisms. In this study, variant calling analysis of RNA-Seq datasets was used to identify single nucleotide polymorphisms (SNPs) in boar spermatozoa and to explore the associations between SNPs and post-thaw semen quality. Assessment of post-thaw sperm quality characteristics showed that 21 boars were considered as having good semen freezability (GSF), while 19 boars were classified as having poor semen freezability (PSF). Variant calling demonstrated that most of the polymorphisms (67%) detected in boar spermatozoa were at the 3’-untranslated regions (3’-UTRs). Analysis of SNP abundance in various functional gene categories showed that gene ontology (GO) terms were related to response to stress, motility, metabolism, reproduction, and embryo development. Genomic DNA was isolated from sperm samples of 40 boars. Forty SNPs were selected and genotyped, and several SNPs were significantly associated with motility and membrane integrity of frozen-thawed (FT) spermatozoa. Polymorphism in SCLT1 gene was associated with significantly higher motility and plasma membrane integrity of FT spermatozoa from boars of the GSF group compared with those of the PSF group. Likewise, polymorphisms in MAP3K20, MS4A2, and ROBO1 genes were significantly associated with reduced cryo-induced lipid peroxidation and DNA damage of FT spermatozoa from boars of the GSF group. Candidate genes with significant SNP associations, including APPL1, PLBD1, FBXO16, EML5, RAB3C, OXSR1,PRICKLE1, and MAP3K20 genes, represent potential markers for post-thaw semen quality, and they might be relevant for future improvement in the selection procedure of boars for cryopreservation. The findings of this study provide evidence indicating that polymorphisms in genes expressed in spermatozoa could be considered as factors associated with post-thaw semen quality.

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.

Addition of insulin-like growth factor I (IGF-I) and reduced glutathione (GSH) to cryopreserved boar semen

The objective of this study was to evaluate the effect of adding reduced glutathione (GSH) to a boar semen freezing extender supplemented with insulin-like growth factor I (IGF-I) or anti-IGF-I. Eight ejaculates from eight boars were extended to obtain insemination doses, which were supplemented with either recombinant human IGF-I (30 ng/mL) or anti-IGF-I (60 ng/mL) shortly after extension. After 24 h of liquid storage at 17 °C, the semen was frozen with or without GSH (5 mM) in the freezing extender for a total of six treatments. Osmotic resistance and acrosome integrity was greater in fresh semen (P <  0.05) soon after adding IGF-I or the anti-IGF-I antibody. After 24 h of cooling, the supplementation with these compounds resulted in an increased (P <  0.05) percentage of sperm with relatively greater mitochondrial activity and reduced the percentage of cells with relatively greater concentrations of superoxide. After thawing, there was a reduction (P <  0.05) in the percentage and fluorescence intensity of sperm with greater quantities of superoxide and peroxide only in samples treated with GSH + IGF-I and GSH + anti-IGF-I. The addition of GSH (alone or in combination with IGF-I or anti-IGF-I), however, reduced the percentage of sperm with an intact acrosome (P < 0.05). The same effect was not observed with IGF-I or anti-IGF-I alone. In conclusion, the addition of IGF-I or anti-IGF-I improved the quality of fresh or liquid-stored semen. Using GSH in the freezing extender improved the antioxidant potential of frozen semen only in combination with IGF-I or an anti-IGF-I antibody.

The implementation of a HACCP system improved the efficiency of a bull semen collection and processing center

Bull Semen Collection and Processing Centers (SCPC) have satisfactory control of sperm quality, but commonly lack standardized quality control of hygiene procedures. This study assessed the impact of implementing a Hazard Analysis and Critical Control Points (HACCP) system in a bull SCPC, comparing microbial counts on various steps of semen processing, semen quality and costs across two periods (before and after the HACCP implementation). After surveying all routine activities of the SCPC, control points were identified, preventive measures were designed and corrective actions were employed, whenever necessary. Six months after HACCP implementation, the system was audited and production data covering two similar periods of two consecutive years were compared. Counts of colony forming units in samples collected from artificial vaginas, flexible tubes from the straw filling machine and from fresh and frozen semen after HACCP implementation were lower than during the previous period (P < 0.05). Improved post-thawing sperm motility, membrane integrity and acrosome integrity (P < 0.0001) and reduced rejection of semen batches and frozen doses were observed after HACCP implementation (P < 0.01), resulting in reduced opportunity costs. Thus, the implementation of a HACCP system in a bull SCPC allowed low-cost production of high-quality semen doses with reduced microbial contamination.

Isolation of subtelomeric sequences of porcine chromosomes for translocation screening reveals errors in the pig genome assembly

Balanced chromosomal aberrations have been shown to affect fertility in most species studied, often leading to hypoprolificacy (reduced litter size) in domestic animals such as pigs. With an increasing emphasis in modern food production on the use of a small population of high quality males for artificial insemination, the potential economic and environmental costs of hypoprolific boars, bulls, rams etc. are considerable. There is therefore a need for novel tools to facilitate rapid, cost-effective chromosome translocation screening. This has previously been achieved by standard karyotype analysis; however, this approach relies on a significant level of expertise and is limited in its ability to identify subtle, cryptic translocations. To address this problem, we developed a novel device and protocol for translocation screening using subtelomeric probes and fluorescence in situ hybridisation. Probes were designed using BACs (bacterial artificial chromosomes) from the subtelomeric region of the short (p-arm) and long (q-arm) of each porcine chromosome. They were directly labelled with FITC or Texas Red (p-arm and q-arm respectively) prior to application of a 'Multiprobe' device, thereby enabling simultaneous detection of each individual porcine chromosome on a single slide. Initial experiments designed to isolate BACs in subtelomeric regions led to the discovery of a series of incorrectly mapped regions in the porcine genome assembly (from a total of 82 BACs, only 45 BACs mapped correctly). Our work therefore highlights the importance of accurate physical mapping of newly sequenced genomes. The system herein described allows for robust and comprehensive analysis of the porcine karyotype, an adjunct to classical cytogenetics that provides a valuable tool to expedite efficient, cost effective food production.

Effect of reduced glutathione supplementation in semen extender on tyrosine phosphorylation and apoptosis like changes in frozen thawed Hariana bull spermatozoa

To provide new insights into the mechanisms through which reduced glutathione (GSH) is able to protect spermatozoa, we tested the hypothesis that cryocapacitation and apoptosis like changes can contribute to the negative effect of freezing and thawing on bull spermatozoa, and that GSH prevent this damage. Having known protective effects of GSH in terms of a potent antioxidant, we evaluated capacitation, tyrosine phosphorylation and apoptosis like changes in bull spermatozoa after freezing and thawing in egg yolk tris glycerol extender containing (0.5m M-GSH-T1 & 1mM GSH-T2) and without GSH serving as the control (C). Forty ejaculates were collected from four Hariana bulls and were pooled due to non significant variations among the bull ejaculates for the evaluation of sperm attributes. Capacitation like changes, tyrosine phosphorylation, localization of tyrosine phosphorylated proteins, apoptosis like changes in terms of mitochondrial transmembrane potential and DNA fragmentation after final dilution, 4h of equilibration at 4°C and 24h after freezing and thawing were evaluated. GSH supplementation at 0.5mM showed significant reduction in B- and AR- pattern spermatozoa during all stages of semen freezing and thawing. Immunoblot revealed six proteins which were tyrosine phosphorylated and protein of 30 and 75kDa (p30, p75) were the major tyrosine phosphorylted proteins. On further analysis, the p30 showed differential variation in intensity in all the three groups after freezing and thawing. Positive immune reactivity for tyrosine phosphorylated proteins was found in neck, middle piece and post-acrosomal regions of spermatozoa. Addition of 0.5mM GSH decreased percentage of spermatozoa showing fragmented DNA and increased the percentage of spermatozoa having high transmembrane mitochondrial potential (P<0.05). This study demonstrates that GSH favours survival of bull spermatozoa by interfering with apoptotic and cryocapacitation pathways, and thereby protects the spermatozoa from deleterious effects of cryopreservation. The findings of the study indicated that GSH at 0.5mM can be effectively used as an additive in bull semen extender for freezing and thawing.

Relationship between Porcine Sperm Motility and Sperm Enzymatic Activity using Paper-based Devices

Mammalian sperm motility has traditionally been analyzed to determine fertility using computer-assisted semen analysis (CASA) systems. To develop low-cost and robust male fertility diagnostics, we created a paper-based MTT assay and used it to estimate motile sperm concentration. When porcine sperm motility was inhibited using sperm enzyme inhibitors for sperm enzymes related to mitochondrial activity and glycolysis, we simultaneously recorded sperm motility and enzymatic reactivity using a portable motility analysis system (iSperm) and a paper-based MTT assay, respectively. When using our paper-based MTT-assay, we calculated the area mean value signal intensity (AMV) to evaluate enzymatic reactivity. Both sperm motility and AMV decreased following treatment with iodoacetamide (IODO) and 3-bromopyruvic acid (3BP), both of which are inhibitors of glycolytic enzymes including glyceraldehyde-3-phosphate dehydrogenase (GAPDH). We found a correlation between recorded motility using iSperm and AMV from our paper-based assay (P < 0.05), suggesting that a sperm-related enzymatic reaction is involved in sperm motility. Under this protocol, MTT reduction was coupled with catalysis of GAPDH and was promoted by electron transfer from NADH. Based on this inhibitor study, sperm motility can be estimated using our paper-based MTT-assay.

Oligo-dT selected spermatozoal transcript profiles differ among higher and lower fertility dairy sires

Spermatozoal messenger RNA (mRNA) has the potential as a molecular marker for sire fertility because this population can reflect gene expression that occurred during spermatogenesis and may have a functional role in early embryonic development. The goal of this study was to compare the oligo-dT selected spermatozoal transcript profiles of higher fertility (Conception Rate (CR) 1.8-3.5) and lower fertility (CR -2.9 to -0.4) sires using Ribonucleic Acid Sequencing (RNA-Seq). A total of 3227 transcripts and 5366 transcripts were identified in the higher and lower fertility populations, respectively. While common transcripts between the two populations were identified (2422 transcripts), several transcripts were also unique to the fertility populations including 805 transcripts that were unique to the higher fertility population and 2944 transcripts that were unique to the lower fertility population. From gene ontological analysis, the transcripts unique to each fertility population differed in Biological Processes (BP), including enrichment of regulatory transcripts for growth and protein kinase activity in the higher fertility bulls. Biological variation in transcript presence among individual sires was also found. Of the candidate fertility spermatozoal transcripts chosen from the RNA-Seq population analysis reported here and previous publications, COX7C was negatively correlated with sire fertility. Using high-throughput sequencing, candidate spermatozoal transcripts were identified for further study as potential markers for sire fertility.

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

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

Efficient Boar Semen Production and Genetic Contribution: The Impact of Low-Dose Artificial Insemination on Fertility

Diluting semen from high fertile breeding boars, and by that inseminating many sows, is the core business for artificial insemination (AI) companies worldwide. Knowledge about fertility results is the reason by which an AI company can lower the concentration of a dose. Efficient use of AI boars with high genetic merit by decreasing the number of sperm cells per insemination dose is important to maximize dissemination of the genetic progress made in the breeding nucleus. However, a potential decrease in fertility performance in the field should be weighed against the added value of improved genetics and, in general, is not tolerated in commercial production. This overview provides some important aspects that influence the impact of low-dose AI on fertility: (i) the importance of monitoring field fertility, (ii) the need for accurate and precise semen assessment, (iii) the parameters that are taken into account, (iv) the application of information from genetic and genomic selection and (v) the optimization when using different AI techniques. Efficient semen production, processing and insemination in combination with increasing use of genetic and genomic applications result in maximum impact of genetic trend.

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.

Morphological study of boar sperm during their passage through the female genital tract

Once deposited in the female tract, sperm face a series of challenges that must be overcome to ensure the presence of an adequate normal sperm population close to the site of fertilization. Our aim was to evaluate the influence of the uterine milieu on boar sperm morphology. In experiment 1, sperm morphology was evaluated in the backflow (60 min after insemination) and within the uterotubal junction (UTJ) (collected ~24 h after insemination) following intrauterine sperm deposition (n = 6) and compared with the morphology of the sperm in the insemination dose. In experiment 2, the influence of the uterine fluid (UF) on sperm morphological modifications was evaluated. For this purpose, ejaculated (n = 4) and epididymal (n = 4) sperm were in vitro incubated with or without UF for 2 and 24 h. In both experiments, sperm were classified as normal, having a cytoplasmic droplet (proximal or distal) or having tail defects. The results of experiment 1 pointed to an increase in morphologically abnormal sperm collected in the backflow (27.70%) and a reduction of the same in the UTJ (2.12%) compared with the insemination dose (17.75%) (P < 0.05). In experiment 2, incubation of ejaculated sperm with UF did not provoke any morphological modifications; however, when epididymal sperm were incubated with UF, a pronounced increase in the percentage of normal sperm was evident after 24 h compared with the initial dose (from 25.77% to 53.58%, P < 0.05), mainly due to distal cytoplasmatic droplet shedding (53.22 vs. 20.20%). In conclusion, almost all the sperm that colonize the UTJ had a normal morphology, with part of the abnormal sperm having been discarded in the backflow and part selected/modified on their way to the oviduct. UF seems to influence cytoplasmic distal droplet removal, as demonstrated previously in seminal plasma.

Enhanced fertility prediction of cryopreserved boar spermatozoa using novel sperm function assessment

Due to reduced fertility, cryopreserved semen is seldom used for commercial porcine artificial insemination (AI). Predicting the fertility of individual frozen ejaculates for selection of higher quality semen prior to AI would increase overall success. Our objective was to test novel and traditional laboratory analyses to identify characteristics of cryopreserved spermatozoa that are related to boar fertility. Traditional post-thaw analyses of motility, viability, and acrosome integrity were performed on each ejaculate. In vitro fertilization, cleavage, and blastocyst development were also determined. Finally, spermatozoa-oviduct binding and competitive zona-binding assays were applied to assess sperm adhesion to these two matrices. Fertility of the same ejaculates subjected to laboratory assays was determined for each boar by multi-sire AI and defined as (i) the mean percentage of the litter sired and (ii) the mean number of piglets sired in each litter. Means of each laboratory evaluation were calculated for each boar and those values were applied to multiple linear regression analyses to determine which sperm traits could collectively estimate fertility in the simplest model. The regression model to predict the percent of litter sired by each boar was highly effective (p < 0.001, r(2) = 0.87) and included five traits; acrosome-compromised spermatozoa, percent live spermatozoa (0 and 60 min post-thaw), percent total motility, and the number of zona-bound spermatozoa. A second model to predict the number of piglets sired by boar was also effective (p < 0.05, r(2) = 0.57). These models indicate that the fertility of cryopreserved boar spermatozoa can be predicted effectively by including traditional and novel laboratory assays that consider functions of spermatozoa.

Individual and seasonal variations in the quality of fractionated boar ejaculates

Reproductive seasonality has been shown to affect the quality of boar semen. In this study, effects of seasonal variations in the characteristics of spermatozoa and seminal plasma (SP) of fractioned ejaculates from individual boars have been investigated. Fractionated ejaculates, designated as fraction 1 (F1), fraction 2 (F2), and fraction 3 (F3), were collected from five mature boars during the autumn-winter (October through March) and spring-summer periods (April through September). A total of 10 fractionated ejaculates (F1, F2, and F3) were collected from each boar within each seasonal period. Assessments of the sperm quality characteristics included computer-assisted sperm analysis motion patterns, mitochondrial membrane potential (MMP), plasma membrane integrity, normal apical ridge acrosomes, and DNA fragmentation. Besides SDS-PAGE and densitometric analyses of the SP proteins, the antiperoxidant activity was monitored. There were marked differences in the sperm quality characteristics among the boars, except for sperm MMP. Distinct seasonal differences (P < 0.05) were observed in the ejaculate volume of F3 during the autumn-winter and spring-summer periods (107.78 ± 5.45 and 87.80 ± 4.75 mL, respectively). Significantly higher (P < 0.05) sperm concentration and the total number of spermatozoa in the fraction were observed during the autumn-winter period. Seasonal effects in MMP and plasma membrane integrity were manifested in significantly higher (P < 0.05) percentages of spermatozoa with functional mitochondria and intact plasma membrane during the autumn-winter period. However, the seasonal effects were less marked in either sperm normal apical ridge acrosomes or sperm DNA fragmentation. Sodium dodecyl sulfate-PAGE and densitometric analyses revealed marked variations in the protein composition of the SP profiles among the boars, regardless of the ejaculate fraction and seasonal period. Distinct seasonal variations, observed in the SDS-PAGE profiles, were associated with an abundance of protein fractions of low-molecular and high-molecular weight components, particularly during the autumn-winter period. There were wide variations in antiperoxidant activity in the SP among the boars, being significantly higher in the autumn-winter period, irrespective of the ejaculate fraction. It can be suggested that marked deterioration of the quality of fractionated ejaculates during the spring-summer period was probably caused by impaired reproductive function in the boar.

Sperm quality and fertility of boar seminal doses after 2 days of storage: does the type of extender really matter?

The present approach was designed to evaluate the extender effects on sperm quality and fertility of short-term refrigerated seminal doses from Landrace boars lodged in husbandry-controlled conditions. For this purpose, we analyzed the sperm quality of seminal doses diluted in short-term (Beltsville Thawing Solution) and extra-long-term (Duragen) extenders from Days 0 to 2 of storage at 17 °C during an 8-month period. Pregnancy rates and litter size were evaluated from double inseminations within an interval of 12 hours (36 and 48 hours of refrigeration) of multiparous females using seminal doses diluted in each extender type. Sperm quality was assessed from the analyses of sperm motility and kinetics, sperm viability, expressed as plasma and acrosome membrane integrity, membrane lipid disorder, intracellular calcium levels, and acrosin activity. Results indicated significant differences between the extenders in the sperm quality of seminal doses. Therefore, the seminal doses diluted in Duragen had higher percentages of progressive motile spermatozoa and membrane-intact spermatozoa than those diluted in Beltsville Thawing Solution throughout all the experimental months. Nevertheless, despite these differences in preserving the sperm quality, pregnancy rates (>90%) and litter sizes (>10 piglets born per litter) were similar between the extenders. Our results had great relevance from a practical point of view because they reported lack of an extender effect on the reproductive performance of seminal doses during short-tem storage.

Value of semen parameters, with special reference to TNF-α, in predicting the quality of boar semen after short-term storage

The aim of this study was to address the question whether changes in boar semen quality after short-term storage could be predicted on the basis of standard semen parameters and TNF-α level determined on the day of semen collection under commercial conditions. Progressive motility showed the highest positive correlation with morphology on day 0 of collection, and progressive motility on day 3 (P < 0.05) showed a negative correlation with acrosome abnormalities (P < 0.05). According to the area under receiver operating characteristics (ROC) curves (AUCs), progressive motility could also be used in predicting semen quality after 3 days of storage (AUC > 0.5; P < 0.05). TNF-α in seminal plasma is the only parameter measured on day 0 to show a significant correlation with the percentage of viable spermatozoa after 3 days of semen storage (r = 0.495, P < 0.05). ROC analysis shows that TNF-α level is helpful in discriminating viability outcome after semen storage (AUC = 0.94, P < 0.001). We can predict with 92.35% certainty that fresh semen samples with more than 150 pg/ml of TNF-α in the seminal plasma will retain more than 85% of viable spermatozoa after 3 days of storage. Thus, TNF-α can contribute to predicting the quality of short-term stored semen.