Laboratory semen assessment and prediction of fertility: still utopia?

Free-radical production after post-thaw incubation of ram spermatozoa is related to decreased in vivo fertility

The aim of the present study was to evaluate the effect of sperm reactive oxygen species (ROS) production and DNA changes on male fertility. For that purpose, six rams with significantly different pregnancy rates were used; these were classified as having high fertility, i.e. 59.4% average pregnancy rate, or low fertility, i.e. 23.1% average pregnancy rate. Sperm quality was assessed after a two-step process of sample thawing followed by an incubation of 2h, either in the freezing extender (37°C) or after dilution in synthetic oviductal fluid (SOF; 38°C, 5%CO2). Sperm viability (YO-PRO-1), ROS production (5-(and-6)-chloromethyl-2',7'-dichlorodihydrofluorescein acetyl ester (CM-H2DCFDA)) and undamaged chromatin (sperm chromatin structure assay, terminal deoxynucleotidyl transferase-mediated dUTP nick-end labelling, chromomycin A3) were evaluated by flow cytometry. Although no significant differences in sperm viability were observed, our results showed increased ROS production during incubation in the freezing extender as well as in SOF medium. Comparison between fertility groups showed significant differences in ROS production after 2h of incubation for the two treatments. Regarding DNA integrity, our results showed no significant differences either between treatments and incubation times or fertility groups. Linear regression analysis showed that ROS production determined by CM-H2DCFDA was a good indicator parameter for in vivo male fertility of SOF-incubated samples, yielding a fair correlation between both parameters (r=-0.92). These results indicate that detection of ROS production by CM-H2DCFDA and flow cytometry after 2h of incubation in SOF could be a useful procedure for predicting fertility of ram spermatozoa.

Dietary n-6:n-3 ratio and Vitamin E improve motility characteristics in association with membrane properties of boar spermatozoa

This study was aimed to evaluate the effects of dietary n-6:n-3 ratio and Vitamin E on the membrane properties and motility characteristics of spermatozoa in boars. Forty Duroc boars were randomly distributed in a 2 × 2 factorial design with two n-6:n-3 ratios (14.4 and 6.6) and two Vitamin E levels (200 and 400 mg kg⁻¹). During 16 weeks of treatment, fresh semen was collected at weeks 0, 8, 12, and 16 for measurements of motility characteristics, contents of fatty acids, membrane properties (membrane fluidity and membrane integrity), and lipid peroxidation of the spermatozoa. The semen was diluted in Beltsville Thawing Solution (BTS) extender and stored at 17°C, and the sperm motility was assessed at 12, 36, 72, and 120 h of storage. The 6.6 n-6:n-3 dietary ratio increased the contents of n-3 polyunsaturated fatty acids (PUFAs) and docosahexaenoic acid (DHA) and improved the membrane integrity and membrane fluidity of the spermatozoa, resulting in notably increased total motility, sperm progressive motility, and velocity parameters of fresh semen. Feeding diet with Vitamin E (400 mg kg⁻¹) prevented sperm lipid peroxidation, and resulted in higher total motility and sperm progressive motility in fresh and liquid stored semen. In conclusion, the adjustment of n-6:n-3 ratio (6.6) and supply of Vitamin E (400 mg kg⁻¹) successfully improved sperm motility characteristics and thus may be beneficial to the fertility of boars, which might be due to the modification of the physical and functional properties of spermatozoa membrane in response to dietary supplementation.

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.

New insights for male infertility revealed by alterations in spermatic function and differential testicular expression of thyroid-related genes

The impact of thyroid hormone (TH) disorders on male reproductive biology has been a controversial issue for many years. Recently, we reported that hypothyroid male rats have a disruption of the seminiferous epithelium, which may compromise spermatogenesis. To improve the understanding of the reproductive pathogenesis of hypothyroidism and hyperthyroidism, male Wistar rats that developed these dysfunctions in adulthood were used as an experimental model. We evaluated the sperm production, reserves, transit time, morphology, and functionality (acrosome integrity, plasma membrane integrity, and mitochondrial activity), and the testicular expression of the TH receptors (Thra1 and Thra2, Thrb1, and Thrb2), deiodinases (Dio2 and Dio3), and the Mct8 transporter (Slc16a2) were assessed by reverse transcription followed by real-time quantitative PCR (RT-qPCR). The results were evaluated statistically by ANOVA and Tukey HSD test (P < 0.05). Hypothyroidism decreased the total and daily sperm productions and increased the sperm transit time through the epididymis, while the sperm functionality was reduced in both thyroid dysfunctions. Regarding the modulation of gene expression in the testis, hypothyroidism increased the expression of Thra1 and decreased the expression of Dio3, and hyperthyroidism increased the expression of Slc16a2. The observed alterations in spermatic production and function and in the expression of the TH receptor, deiodinase, and the TH transporter are suggestive of TH participation in spermatogenesis in adulthood.

Effect of season on semen quality parameters in Murrah buffalo

Seasonal influence on frozen semen quality in Murrah buffalo breeding bulls was determined. Frozen semen samples of 6 Murrah buffalo bulls were collected and semen frozen in 4 different seasons, viz. winter (Dec-Feb), spring (mid Feb-Apr), summer (May-Jun) and rainy (Jul-Aug) were assessed. Samples (12) of each bull, in a season, were evaluated for sperm motility, viability and acrosome integrity. Motility and other kinematics of spermatozoa during incubation (37°C) at 0, 30, 60, 90 and 120 min of thawing were assessed with computer assisted semen analyzer. Post-thaw sperm total motility and viability differed significantly among the seasons, the highest was in winter. Sperm plasma membrane integrity, acrosome integrity, progressive motility, rapid motility and other CASA evaluated parameters did not differ significantly among the seasons. Higher values of plasma membrane integrity (PMI), progressive motility, rapid motility, average path velocity (VAP), straight line velocity (VSL), curvilinear velocity (VCL), beat cross frequency (BCF), linearity (LIN) and straightness (STR) were obtained in winter season as compared to other seasons. Post-thaw motility at 0 min and 60 min of post-thaw incubation varied significantly between seasons and higher sperm motility was sustained for a longer period in semen cryopreserved in winter followed by rainy season, summer and spring. It can be concluded from this study that buffalo bull semen produced and frozen during winter season resulted in higher sperm motility, viability and postthaw longer survivability in comparison to other seasons.

Effect of chamber characteristics, loading and analysis time on motility and kinetic variables analysed with the CASA-mot system in goat sperm

Several factors unrelated to the semen samples could be influencing in the sperm motility analysis. The aim of the present research was to study the effect of four chambers with different characteristics, namely; slide-coverslip, Spermtrack, ISAS D4C10, and ISAS D4C20 on the sperm motility. The filling procedure (drop or capillarity) and analysis time (0, 120 and 240s), depth of chamber (10 or 20μm) and field on motility variables were analysed by use of the CASA-mot system in goat sperm. Use of the drop-filling chambers resulted in greater values than capillarity-filling chambers for all sperm motility and kinetic variables, except for LIN (64.5% compared with 56.3% of motility for drop- and capillarity-filling chambers respectively, P<0.05). There were no significant differences in total sperm motility between different chamber depths, however, use of the 20μm-chambers resulted in greater sperm progressive motility rate, VSL and LIN, and less VCL and VAP than chambers with a lesser depth. There was less sperm motility and lesser values for kinetic variables as time that elapsed increased between sample loading and sperm evaluation. For sperm motility, use of droplet-loaded chambers resulted in similar values of MOT in all microscopic fields, but sperm motility assessed in capillarity-loaded chambers was less in the central fields than in the outermost microscopic fields. For goats, it is recommended that sperm motility be analysed using the CASA-mot system with a drop-loaded chamber within 2min after filling the chamber.

Short communication: Progressive motility of frozen-thawed canine semen is highest five minutes after thawing

Progressive motility is usually estimated by visual inspection using a light contrast microscope at X 100 immediately after semen collection or immediately after thawing frozen semen. Standard operating procedures have never been established for this test. The objective of this experiment was to examine time-dependent changes of motility after thawing cryopreserved canine semen. Semen of 35 dogs was collected, and volume, concentration, progressive motility, morphology, membrane integrity and HOS test were evaluated. For cryopreservation, CaniPRO^® Freeze A&B was used. Semen was thawed and diluted using CaniPRO^® culture medium. After thawing, semen was evaluated as before. In addition, every sample was evaluated for progressively motile sperm cells 0, 5, 20 and 60 min after thawing. Progressive semen motility was significantly highest five minutes after thawing.

Quality of fresh and chilled-stored raccoon dog semen and its impact on artificial insemination efficiency

Background

The aim of the study was to evaluate the quality of fresh raccoon dog semen and raccoon dog semen stored at 4 °C. The qualitative evaluation was based on apoptosis in the sperm cells, which was tested by the Annexin V/Pi assay, the TUNEL method and JC-1. In addition, the suitability of the semen for insemination and its effect on reproduction in females were determined in relation to the time of storage.

Results

During cold storage of the semen, in the samples from all groups a gradual decrease was noted in the percentage of live cells, and an increase in the percentage of cells with abnormal morphology, exhibiting changes typical of late-stage apoptosis (V⁺/PI⁺), and of necrotic cells (V⁻/PI⁺). There was a significant increase in the percentage of ApoBrDu + sperm cells, while the mitochondrial membrane potential of the sperm decreased significantly after 12 h of storage at 4 °C in the case of lower-quality semen and after 48 h in the case of semen of good quality. As the percentage of sperm with DNA and cell membrane damage increased and the mitochondrial membrane potential decreased, there was an increase in AspAT and acrosin activity. The increase in the percentage of apoptotic sperm in the raccoon dog semen stored at 4 °C resulted in a decrease in the number of females with cubs.

Conclusions

Identification of apoptotic changes in sperm by flow cytometry using the annexin assay, the TUNEL assay and evaluation of mitochondrial membrane potential can be recommended for determination of the suitability of raccoon dog semen for artificial insemination. The study shows that fresh raccoon dog semen should not be used for insemination more than 48 h after collection in the case of semen of very high quality, or after more than 24 h in the case of semen of poorer quality. Cytometric methods of semen analysis should also be used to evaluate various extenders of raccoon dog semen and methods of cryopreservation in terms of ensuring sperm viability, fertilization capacity, and suitability for insemination.

Maintaining semen quality by improving cold chain equipment used in cattle artificial insemination

Artificial insemination of dairy cattle is a common practice in the developing world that can improve farmer incomes and food security. Maintaining the fertilizing potential of frozen semen as it is manipulated, transported and stored is crucial to the success of this process. Here we describe simple technological improvements to protect semen from inadvertent thermal fluctuations that occur when users mishandle semen using standard equipment. We show that when frozen semen is mishandled, characteristics of semen biology associated with fertility are negatively affected. We describe several design modifications and results from thermal performance tests of several improved prototypes. Finally, we compare semen that has been mishandled in standard and improved equipment. The data suggest that our canister improvements can better maintain characteristics of semen biology that correlate with fertility when it is mishandled.

Differential abundances of four forms of Binder of SPerm 1 in the seminal plasma of Bos taurus indicus bulls with different patterns of semen freezability

The Binder of SPerm 1 (BSP1) protein is involved in the fertilization and semen cryopreservation processes and is described to be both beneficial and detrimental to sperm. Previously, the relationship of BSP1 with freezability events has not been completely understood. The objective of this work was to determine the differential abundance of the forms of the BSP1 protein in cryopreserved seminal plasma of Bos taurus indicus bulls with different patterns of semen freezability using proteomics. A wide cohort of adult bulls with high genetic value from an artificial insemination center was used as donors of high quality, fresh semen. Nine bulls presenting different patterns of semen freezability were selected. Two-dimensional gel electrophoresis showed differential abundance in a group of seven protein spots in the frozen/thawed seminal plasma from the bulls, ranging from 15 to 17 kDa, with pI values from 4.6 to 5.8. Four of these spots were confirmed to be BSP1 using mass spectrometry, proteomics, biochemical, and computational analysis (Tukey's test at P < 0.05). The protein spot weighing 15.52 ± 0.53 kDa with a pI value of 5.78 ± 0.12 is highlighted by its high abundance in bulls with low semen freezability and its absence in bulls presenting high semen freezability. This is the first report showing that more than two forms of BSP1 are found in the seminal plasma of Nelore adult bulls and not all animals have a similar abundance of each BSP1 form. Different BSP1 forms may be involved in different events of fertilization and the cryopreservation process.

Effect of Trolox on sperm quality in normozospermia and oligozospermia during cryopreservation

This study evaluated the effects of different concentrations of Trolox supplementation to cryoprotective agent (CPA) on post-thaw apoptosis-like events that include translocation of phosphatidyl serine (PS) to the cell surface, alterations in mitochondrial membrane potential (MMP), and DNA integrity of normozoospermic and oligoozoospermic semen samples. Spermatozoa from 20 normozoospermic men and 20 patients with oligoozoospermia were cryopreserved with cryo-protective agent containing 0, 20, 40, and 80 μM Trolox. Pre-cryopreservation and post-thaw sperm MMP, PS externalization and DNA fragmentation were evaluated by flow cytometry. Sperm frozen in extender with Trolox had greater MMP, lower DNA fragmentation and externalization of PS in both groups, though the most effective dose of Trolox in normozoospermic and oligoozoospermic semen samples were different. These findings support the use of Trolox as freezing extender supplement to improve the quality of cryopreserved human sperm, measured in terms of early apoptosis changes and DNA integrity, in both normozoospermic and oligoozoospermic men.

Sperm macromolecules associated with bull fertility

Bull fertility, ability of the sperm to fertilize and activate the egg that sustain embryo development, is vitally important for effective and efficient production of cattle. Fertility is a complex trait with low heritability. Despite recent advances in genomic selection and possibility of enormous paternal benefits to profitable cattle production, there exist no reliable tests for evaluating semen quality and predicting bull fertility. This review focuses on sperm macromolecules such as transcripts, proteins and the epigenome, i.e., the functional genome that are associated with bull fertility. Generating new information in these systems is important beyond agriculture because such progress advances the fundamental science of the mammalian male gamete while at the same time introduces biotechnology into livestock production. Sperm macromolecules and epigenome markers associated with bull fertility can be used alone or in combination with the current SNP microarrays to determine sperm quality and to indicate bull fertility.

Stress preconditioning of semen before cryopreservation improves fertility and increases the number of offspring born: a prospective randomised study using a porcine model

The aim of the present study was to investigate the effect of applying sublethal stress treatment at room temperature, before cryopreservation (hydrostatic pressure (HP): 40 MPa, 80 min) of 34 boar ejaculate samples, on post-thawed motility and sow fertility. Sows (n = 102) were randomly allocated into equal groups inseminated with HP-treated or untreated frozen–thawed semen. Sows were inseminated twice, 10 h apart, with 6 × 109 spermatozoa per dose without oestrus synchronisation. Rates of non-return of oestrus and pregnancy, and total numbers of piglets and live piglets were significantly higher (P < 0.05) in the HP-treated group. There was also a numerical, albeit non-significant (P > 0.05), improvement in the farrowing rate in the HP-treated group. Although the number of live piglets per litter decreased approximately 15% in both groups by 42 days after farrowing, but this remained significantly higher in the HP-treated group. Although total and progressive sperm motility were significantly (P < 0.001) higher in the HP-treated group, there were no significant differences (P > 0.05) in these parameters between pregnant and non-pregnant sows in either group; thus motility can indicate, but not predict, improved fertility. In conclusion, HP treatment, with sperm cryopreservation, increases in vitro sperm motility and improves reproductive performance without adversely affecting the health of the piglets.

The effect of the freezing curve type on bull spermatozoa motility after thawing

The objective of this work was to determine the effect of selected freezing curves on spermatozoa survivability after thawing, defined by its motility. The ejaculates of nine selected sires of the same age, breed, and frequency of collecting, bred under the same breeding conditions including handling, stabling, feeding system and feeding ratio composition, were repeatedly collected and evaluated. Sperm samples of each sire were diluted using only one extender and divided into four parts. Selected four freezing curves – the standard, commercially recommended three-phase curve; a two-phase curve; a slow three-phase curve; and a fast three-phase curve, differing in the course of temperature vs time, were applied. The percentage rate of progressive motile spermatozoa above head was determined immediately after thawing, and after 30, 60, 90, and 120 min of the thermodynamic test (TDT). Moreover, average spermatozoa motility (AMOT) and spermatozoa motility decrease (MODE) throughout the entire TDT were evaluated. Insemination doses frozen using the simpler two-phase curve demonstrated the highest motility values (+2.97% to +10.37%; P < 0.05–0.01) immediately after thawing and during the entire TDT. Concurrently, the highest AMOT (+4.37% to +8.82%; P < 0.01) was determined. The highest spermatozoa motility values were detected after thawing doses frozen by the two-phase freezing curve in eight out of nine sires. Simultaneously, a significant effect of sire individuality was clearly confirmed. Inter-sire differences of spermatozoa motility during TDT as well as AMOT and MODE were significant (P < 0.01). The findings describing both factors of interaction indicate the necessity of individual cryopreservation of the ejaculate to increase its fertilization capability after thawing.

Mass sperm motility is associated with fertility in sheep

The study was to focus on the relationship between wave motion (mass sperm motility, measured by a mass sperm motility score, manually assessed by artificial insemination (AI) center operators) and fertility in male sheep. A dataset of 711,562 artificial inseminations performed in seven breeds by five French AI centers during the 2001-2005 time period was used for the analysis. Factors influencing the outcome of the insemination, which is a binary response observed at lambing of either success (1) or failure (0), were studied using a joint model within each breed and AI center (eight separate analyses). The joint model is a multivariate model where all information related to the female, the male and the insemination process were included to improve the estimation of the factor effects. Results were consistent for all analyses. The male factors affecting AI results were the age of the ram and the mass motility. After correction for the other factors of variation, the lambing rate increased quasi linearly from three to more than ten points with the mass sperm motility score depending on the breed and the AI center. The consistency of the relationship for all breeds indicated that mass sperm motility is predictive of the fertility resulting when sperm are used from a specific ejaculate. Nonetheless, predictability could be improved if an objective measurement of mass sperm motility were available as a substitute for the subjective scoring currently in use in AI centers.

Effect of single-layer centrifugation or washing on frozen-thawed donkey semen quality: Do they have the same effect regardless of the quality of the sample?

The aims of this study were to determine the sperm quality of frozen-thawed donkey sperm samples after single-layer centrifugation (SLC) using Androcoll-E in comparison to sperm washing or no centrifugation and to determine if the effect on the sperm quality after SLC or sperm washing depends on the quality of the sample. Frozen-thawed sperm samples from Andalusian donkeys were divided into three aliquots, and they were processed using three different techniques after thawing: uncentrifuged diluted control (UDC), sperm washing (SW), and SLC. Afterward, sperm quality index was estimated by integrating all parameters (total and progressive sperm motility, membrane integrity, and DNA fragmentation) in a single value. The relationship between the sperm quality of thawed UDC samples and the effect on sperm parameters in SW and SLC-selected samples was assessed. Sperm quality index was significantly higher (P < 0.001) in SLC (0.8 ± 0.0) samples than that in UDC (0.6 ± 0.0) and SW (0.6 ± 0.0) samples, regardless of the sperm quality index after thawing of the sperm sample. In conclusion, SLC of frozen-thawed donkey spermatozoa using Androcoll-E-Small can be a suitable procedure for selecting frozen-thawed donkey sperm with better quality, in particular in those samples where an improvement in motility is needed.

Adult exposure to bisphenol A (BPA) in Wistar rats reduces sperm quality with disruption of the hypothalamic-pituitary-testicular axis

Reproductive physiology involves complex biological processes that can be disrupted by exposure to environmental contaminants. The effects of bisphenol A (BPA) on spermatogenesis and sperm quality is still unclear. The objective of this study was to investigate the reproductive toxicity of BPA at dosages considered to be safe (5 or 25mg BPA/kg/day). We assessed multiple sperm parameters, the relative expression of genes involved in the central regulation of the hypothalamic-pituitary-testicular axis, and the serum concentrations of testosterone, estradiol, LH and FSH. BPA exposure reduced sperm production, reserves and transit time. Significant damage to the acrosomes and the plasma membrane with reduced mitochondrial activity and increased levels of defective spermatozoa may have compromised sperm function and caused faster movement through the epididymis. BPA exposure reduced the serum concentrations of testosterone, LH and FSH and increased the concentration of estradiol. The relative gene expression revealed an increase in gonadotropin releasing hormone receptor (Gnrhr), luteinizing hormone beta (Lhb), follicle stimulating hormone beta (Fshb), estrogen receptor beta (Esr2) and androgen receptor (Ar) transcripts in the pituitary and a reduction in estrogen receptor alpha (Esr1) transcripts in the hypothalamus. In this study, we demonstrated for the first time that adult male exposure to BPA caused a reduction in sperm production and specific functional parameters. The corresponding pattern of gene expression is indicative of an attempt by the pituitary to reestablish normal levels of LH, FSH and testosterone serum concentrations. In conclusion, these data suggest that at dosages previously considered nontoxic to reproductive function, BPA compromises the spermatozoa and disrupts the hypothalamic-pituitary-gonadal axis, causing a state of hypogonadotropic hypogonadism.

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

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

Impact of swine reproductive technologies on pig and global food production

Reproductive technologies have dramatically changed the way pigs are raised for pork production in developed and developing countries. This has involved such areas as pigs produced/sow, more consistent pig flow to market, pig growth rate and feed efficiency, carcass yield and quality, labor efficiency, and pig health. Some reproductive technologies are in widespread use for commercial pork operations [Riesenbeck, Reprod Domest Anim 46:1-3, 2011] while others are in limited use in specific segments of the industry [Knox, Reprod Domest Anim 46:4-6, 2011]. Significant changes in the efficiency of pork production have occurred as a direct result of the use of reproductive technologies that were intended to improve the transfer of genes important for food production [Gerrits et al., Theriogenology 63:283-299, 2005]. While some technologies focused on the efficiency of gene transfer, others addressed fertility and labor issues. Among livestock species, pig reproductive efficiency appears to have achieved exceptionally high rates of performance (PigCHAMP 2011) [Benchmark 2011, Ames, IA, 12-16]. From the maternal side, this includes pigs born per litter, farrowing rate, as well as litters per sow per year. On the male side, boar fertility, sperm production, and sows served per sire have improved as well [Knox et al., Theriogenology, 70:1202-1208, 2008]. These shifts in the efficiency of swine fertility have resulted in the modern pig as one of the most efficient livestock species for global food production. These reproductive changes have predominantly occurred in developed countries, but data suggests transfer and adoption of these in developing countries as well (FAO STAT 2009; FAS 2006) [World pig meat production: food and agriculture organization of the United Nations, 2009; FAS, 2006) Worldwide Pork Production, 2006]. Technological advancements in swine reproduction have had profound effects on industry structure, production, efficiency, quality, and profitability. In all cases, the adoption of these technologies has aided in the creation of a sustainable supply of safe and affordable pork for consumers around the world [den Hartog, Adv Pork Prod 15:17-24, 2004].

Fertilization capacity of cryopreserved Iberian ibex epididymal sperm in a heterologous in vitro fertilization assay

In vitro fertilization (IVF) can be used to assess the fertilization capacity of sperm. Heterologous IVF may be useful when assessing that of wild animals as it is often difficult to obtain adequate numbers of naturally corresponding oocytes. The aim of the present study was to assess the fertilization capacity of frozen–thawed ibex epididymal spermatozoa via heterologous IVF involving the oocytes of prepubertal domestic goats. The effect on fertilization and embryo development of adding oestrous sheep serum (ESS) to the fertilization medium was also examined. Cumulus–oocyte complexes (COCs) were matured in TCM-199 for 24–27 h at 38.5°C in a 5% CO2 in air atmosphere. Frozen–thawed epididymal spermatozoa were selected by density gradient centrifugation. After maturation, the oocytes were co-incubated with spermatozoa in synthetic oviductal fluid (SOF) with different concentrations of ESS: SOF-C (0%), SOF-2 (2%) and SOF-20 (20%). At 17 h post-insemination (hpi), zygotes with one female and one male pronucleus (2PN) were categorised as normal; zygotes with 3PN were recorded as polyspermic, and oocytes with 1PN as asynchronous. Cleavage and blastocyst development were assessed at 48 and 168 hpi respectively. The percentage of zygotes with 2PN was higher in the SOF-2 than in the SOF-20 treatment group (27.7% versus 2.9% P < 0.05). The percentage of blastocysts formed with the SOF-C, SOF-2 and SOF-20 treatments were 1.1%, 7.5% and 0% respectively. These results show that the presence of 2% ESS achieves better results than the use of no serum or the standard 20% concentration. Heterologous IVF may be an effective method for predicting the fertilization capacity of ibex spermatozoa, and therefore perhaps that of other wild mountain ungulates.

Relationship between conventional semen characteristics, sperm motility patterns and fertility of Andalusian donkeys (Equus asinus)

Sperm quality has an important role in determining fertility. The aims of this study were to compare the conventional sperm parameters, plus the characteristics of the motility patterns of the different sperm subpopulations, of donkey donors with different fertility level, and to determine their relationships to fertility. Thirty ejaculates from 6 Andalusian donkeys were assessed for gel-free volume, pH, sperm concentration, motility and morphology. The fertility of donkeys was classified on the basis of pregnancy rates per cycle, where donkeys with a per cycle pregnancy rate ≥60% were considered to be "fertile" (n=3) and those with a per cycle pregnancy rate <40% were categorized to be "sub-fertile" (n=3). Significant differences (P<0.001) between the "fertile" and the "sub-fertile" group were found for total and progressive motility, and for straight line velocity. Sperm variables associated (P<0.05) with an increase in percent pregnant per cycle included total motility (r=0.37), progressive motility (r=0.53), curvilinear velocity (r=0.44), straightness (r=0.39), beat cross frequency (r=0.44), and gel-free volume (r=0.53). Four sperm subpopulations (sP) were identified in fresh semen: sP1 (slow and non-progressive spermatozoa, 20%), sP2 (moderately slow but progressive spermatozoa, 71.2%), sP3 (highly active but non-progressive spermatozoa, 2.9%), and sP4 (highly active and progressive spermatozoa, 5.9%). The lowest percentage (3.1%; P<0.001) of sP4 spermatozoa was observed in the "sub-fertile" group. Three of the sperm subpopulations were related (P<0.05) to fertility (sP2, r=0.54; sP3, r=0.45; sP4, r=0.56). In conclusion, we were able to relate the fertility of donkeys with in vitro measures of sperm motility using computer-assisted sperm analysis techniques.

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.

Absolute copy number differences of Y chromosomal genes between crossbred (Bos taurus × Bos indicus) and Indicine bulls

Background

The Y chromosome in mammal is paternally inherited and harbors genes related to male fertility and spermatogenesis. The unique intra-chromosomal recombination pattern of Y chromosome and morphological difference of this chromosome between Bos taurus and Bos indicus make it an ideal model for studying structural variation, especially in crossbred (Bos taurus × Bos indicus) bulls. Copy Number Variation (CNV) is a type of genomic structural variation that gives information complementary to SNP data. The purpose of this study was to find out copy number differences of four Y chromosomal spermatogenesis-related candidate genes in genomic DNA of crossbred and purebred Indicine bulls.

Result

Four Y chromosomal candidate genes of spermatogenesis namely, sex determining gene on Y chromosome (SRY), DEAD box polypeptide 3-Y chromosome (DDX3Y), Ubiquitin specific peptidase 9, Y-linked (USP9Y), testis-specific protein on Y chromosome (TSPY) were evaluated. Absolute copy numbers of Y chromosomal genes were determined by standard curve-based quantitative real time PCR. Copy numbers of SRY and TSPY genes per unit amount of genomic DNA are higher in crossbred than Indicine bulls. However, no difference was observed in DDX3Y and USP9Y gene copy numbers between two groups.

Conclusion

The present study demonstrates that the structural organization of Y chromosomes differs between crossbred and Indicine bulls which are reproductively healthy as observed from analysis of semen attributes. The absolute copy numbers of SRY and TSPY genes in unit mass of genomic DNA of crossbred bulls are significantly higher than Indicine bulls. No alteration in absolute copies of DDX3Y and USP9Y gene was found between the genome of crossbred and Indicine bulls. This study suggests that the DDX3Y and USP9Y are likely to be single copy genes in the genome of crossbred and Indicine bulls and variation in Y chromosome length between crossbred and Indicine bulls may be due to the copy number variation of SRY gene and TSPY array.

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.

Assessment of in vitro sperm characteristics and their importance in the prediction of conception rate in a bovine timed-AI program

The aims of this study were to assess in vivo fertility and in vitro sperm characteristics of different sires and to identify sperm variables important for the prediction of conception rate. Multiparous Nelore cows (n = 191) from a commercial farm underwent the same timed artificial insemination (timed-AI) protocol. Three batches of frozen semen from three Angus bulls were used (n = 9). A routine semen thawing protocol was performed in the laboratory to mimic field conditions. The following in vitro sperm analyses were performed: Computer Assisted Semen Analysis (CASA), Thermal Resistance Test (TRT), Hyposmotic Swelling Test (HOST), assessment of plasma and acrosomal membrane integrity, assessment of sperm plasma membrane stability and of lipid peroxidation by flow cytometry and assessment of sperm morphometry and chromatin structure by Toluidine Blue staining. For statistical analyses, Partial Least Squares (PLS) regression was used to explore the importance of various sperm variables in the prediction of conception rate. The following in vitro sperm variables were determined to be important predictors of conception rate: total motility (TM), progressive motility (PM), TM after 2 h of thermal incubation (TM_2 h), PM after 2 h of thermal incubation (PM_2 h), Beat Cross Frequency after 2 h of thermal incubation (BCF_2 h), percentage of rapidly moving cells after 2 h of thermal incubation (RAP_2 h), intact plasma membrane evaluated by HOST, intact plasma and acrosomal membranes evaluated by flow cytometry, intact plasma membrane suffering lipid peroxidation, major defects, total defects, morphometric width/length ratio, Fourier_0 and Fourier_2 and Chromatin Heterogeneity. We concluded that PLS regression is a suitable statistical method to identify in vitro sperm characteristics that have an important relationship with in vivo bull fertility.

Ram Sperm Selection by a Dextran/Swim-Up Procedure Increases Fertilization Rates Following Intrauterine Insemination in Superovulated Ewes

The objective of this study was to compare the efficacy of 2 dextran/swim-up media to increase the sperm quality parameters and the maintenance of these parameters at 15 degrees C and 30 degrees C over 6 hours. Additionally, this study examined whether differences in sperm quality reflect different reproductive efficiencies following intrauterine insemination in superovulated ewes. The study involved 2 selected samples (SS) obtained by dextran/swim-up, performed either with (SS+) or without (SS-) capacitating compounds, and a control sample consisting of raw semen diluted in the same medium. The efficacies of the swim-up sperm selection procedures were similar in both media, and no significant differences were found among the evaluated parameters. Conversely, we found important differences between selected and control samples. Sperm motility, viability (as assessed by carboxifluorescein diacetate/propidium iodide [PI] staining), and mitochondrial activity (as assessed by rhodamine 123/PI) were significantly higher in the selected samples than in the control. Additionally, following incubation at 15 degrees C, the preservation of sperm quality was significantly better in the selected samples than in the control samples. After 6 hours of incubation at 15 degrees C, selected samples had a motility value of 46%, which was significantly (P < .001) higher than the value observed in control samples (27%). The percentage of viable cells observed after 6 hours of incubation at 15 degrees C was significantly (P < .0001) higher in selected samples than in the control samples. Furthermore, after 2 hours of incubation at 30 degrees C, swim-up samples had viability values that were significantly (P < .0001) higher than those of the control samples. SS+ and SS- samples did not differ significantly in spermatozoa yield, sperm quality, or survival. Differences between selected samples and controls were reflected in the fertilization rate obtained following intrauterine insemination in superovulated ewes that experienced a 52-hour interval between progestagen removal and artificial insemination. A restricted criterion for fertilization rate evaluation was established, and only the percentage of embryos recovered from the uterine horns 6 days after insemination was considered with respect to the total number of corpora lutea counted in the ovaries. The fertilization rate of SS- samples (50%) was significantly higher (P > .001) than those of the SS+ (2%) and control samples (5%).

Semen quality assessments and their significance in reproductive technology

Semen quality assessment methods are very important in predicting the fertilizing ability of persevered spermatozoa and to improve animal reproductive technology. This review discusses some of the current laboratory methods used for semen quality assessments, with references to their relevance in the evaluation of male fertility and semen preservation technologies. Semen quality assessment methods include sperm motility evaluations, analyzed with the computer-assisted semen analysis (CASA) system, and plasma membrane integrity evaluations using fluorescent stains, such as Hoechst 33258 (H33258), SYBR-14, propidium iodide (PI), ethidium homodimer (EthD) and 6-carboxyfluorescein diacetate (CFDA), and biochemical tests, such as the measurement of malondialdehyde (MDA) level. This review addresses the significance of specific fluorochromes and ATP measurements for the evaluation of the sperm mitochondrial status. Laboratory methods used for the evaluation of chromatin status, DNA integrity, and apoptotic changes in spermatozoa have been discussed. Special emphasis has been focused on the application of proteomic techniques, such as two-dimensional (2-D) gel electrophoresis and liquid chromatography mass spectrometry (LC-MS/MS), for the identification of the properties and functions of seminal plasma proteins in order to define their role in the fertilization-related processes.

Delivering value from sperm proteomics for fertility

Fertilization of an egg by a spermatozoon sets the stage for mammalian development. Viable sperm are a prerequisite for successful fertilization and beyond. Spermatozoa have a unique cell structure where haploid genomic DNA is located in a tiny cytoplasmic space in the head, mitochondria in the midpiece and then the tail, all enclosed by several layers of membrane. Proteins in sperm play vital roles in motility, capacitation, fertilization, egg activation and embryo development. Molecular defects in these proteins are associated with low fertility or in some cases, infertility. This review will first summarize genesis, molecular anatomy and physiology of spermatozoa, fertilization, embryogenesis and then those proteins playing important roles in various aspects of sperm physiology.

Assisted reproductive techniques for cattle breeding in developing countries: a critical appraisal of their value and limitations

Commercialization of animal biotechnologies, including those related to reproduction [also known as assisted reproductive techniques (ARTS)], is an increasing reality in developing countries, following the enormous flow of information around us and the increasing global commercial interests in areas where cattle production has its major assets. The present review discusses the achievements of various biotechnological tools for reproduction in cattle including semen handling for artificial insemination (AI), superovulation and embryo transfer (MOET), in vitro handling of oocytes and production of embryos, reproductive cloning and emerging technologies (sex selection, gene targeting and nuclear transfer for livestock transgenesis, genomics for marker-assisted selection, etc.). The application of these technologies for cattle breeding is critically discussed in relation to their impact in the improvement of the efficiency of dairy and beef production in developed and - particularly - in developing countries, which ultimately rule the possibilities of a competitive and sound production of food for human consumption. Despite the remarkable progress made and the punctual importance of some of the above-mentioned technologies, AI remains the most important assisted reproductive technology (ART) in developing countries. Any attempt to gain widespread of any other ART under the predominant economical conditions in developing countries ought to match the simplicity and the success of AI as a breeding tool.