Fertility estimation: a review of past experience and future prospects

Sperm morphology and forward motility are indicators of reproductive success and are not age- or condition-dependent in a captive breeding population of endangered snake

The relationship between male ejaculate traits and reproductive success is an important consideration for captive breeding programs. A recovery plan for the endangered Louisiana pinesnake includes captive breeding for the release of young to the wild. Semen was collected from twenty captive breeding male snakes and ejaculate traits of motility, morphology, and membrane viability were measured for each male. Semen traits were analyzed in relation to the fertilization rate of eggs produced from pairings of each male with a single female (% fertility) to determine the ejaculate factors contributing to reproductive success. In addition, we investigated the age- and condition-dependence of each ejaculate trait. We found significant variation in the ejaculate traits of males and normal sperm morphology ([Formula: see text] = 44.4 ± 13.6%, n = 19) and forward motility ([Formula: see text] = 61.0 ± 13.4%, n = 18) were found to be the best predictors of fertility. No ejaculate traits were found to be condition-dependent (P > 0.05). Forward progressive movement (FPM) ([Formula: see text] = 4 ± 0.5, n = 18) was determined to be age-dependent (r2 = 0.27, P = 0.028), but FPM was not included in the best model for rate of fertilization. Male Louisiana pinesnakes do not appear to experience a significant decline in reproductive potential with age (P > 0.05). The observed average rate of fertilization in the captive breeding colony was below 50% and only those pairings with a male having >51% normal sperm morphology avoided a 0% rate of fertilization. Identification of the factors contributing to the reproductive success of captive breeding Louisiana pinesnakes is of considerable conservation value in the recovery of the species, and captive breeding programs should use assessments of ejaculate traits to plan breeding pairs for maximum reproductive output.

Label-Free Microfluidic Impedance Cytometry for Acrosome Integrity Assessment of Boar Spermatozoa

Microfluidics and lab-on-chip technologies have been used in a wide range of biomedical applications. They are known as versatile, rapid, and low-cost alternatives for expensive equipment and time-intensive processing. The veterinary industry and human fertility clinics could greatly benefit from label-free and standardized methods for semen analysis. We developed a tool to determine the acrosome integrity of spermatozoa using microfluidic impedance cytometry. Spermatozoa from boars were treated with the calcium ionophore A23187 to induce acrosome reaction. The magnitude, phase and opacity of individual treated and non-treated (control) spermatozoa were analyzed and compared to conventional staining for acrosome integrity. The results show that the opacity at 19 MHz over 0.5 MHz is associated with acrosome integrity with a cut-off threshold at 0.86 (sensitivity 98%, specificity 97%). In short, we have demonstrated that acrosome integrity can be determined using opacity, illustrating that microfluidic impedance cytometers have the potential to become a versatile and efficient alternative in semen analysis and for fertility treatments in the veterinary industry and human fertility clinics.

An Update on Semen Physiology, Technologies, and Selection Techniques for the Advancement of In Vitro Equine Embryo Production: Section II

Simple Summary

In order to improve fertilization and pregnancy rates within artificial insemination or in vitro fertilization techniques in horses, producers may choose to select the best sperm within an ejaculate. In this paper, we review conventional and novel methods of sperm selection.

Abstract

As the use of assisted reproductive technologies (ART) and in vitro embryo production (IVP) expand in the equine industry, it has become necessary to further our understanding of available semen selection techniques. This segment of our two-section review will focus on the selection of spermatozoa based on quality and sex for equine intracytoplasmic sperm injection (ICSI), as well as current and future developments in sperm sorting technologies. Ultimately, novel methods of semen selection will be assessed based on their efficacy in other species and their relevance and future application towards ARTs in the horse.

Genome-wide association and genomic prediction for scrotal circumference in Hereford and Braford bulls

Scrotal circumference (SC) is widely used as a selection criterion for bulls in breeding programs, since it is easily assessed and correlated with several desirable reproductive traits. The objectives of this study were: to perform a genome-wide association study (GWAS) to identify genomic regions associated with SC adjusted for age (SCa) and for both age and weight (SCaw); to select Tag SNPs from GWAS to construct low-density panel for genomic prediction; and to compare the prediction accuracy of the SC through different methods for Braford and Hereford bulls from the same genetic breeding program. Data of SC from 18,172 bulls (30.4 ± 3.7 cm) and of genotypes from 131 sires and 3,545 animals were used. From GWAS, the top 1% of 1-Mb windows were observed on chromosome (BTA) 2, 20, 7, 8, 15, 3, 16, 27, 6 and 8 for SCa and on BTA 8, 15, 16, 21, 19, 2, 6, 5 and 10 for SCaw, representing 17.4% and 18.8% of the additive genetic variance of SCa and SCaw, respectively. The MeSH analysis was able to translate genomic information providing biological meanings of more specific gene functions related to the SCa and SCaw. The genomic enhancement methods, especially single step GBLUP, that combined phenotype and pedigree data with direct genomic values generated gains in accuracy in relation to pedigree BLUP, suggesting that genomic predictions should be applied to improve genetic gain and to narrow the generation interval compared to traditional methods. The proposed Tag-SNP panels may be useful for lower-cost commercial genomic prediction applications in the future, when the number of bulls in the reference population increases for SC in Hereford and Braford breeds.

Effects of Extender Type, Storage Time, and Temperature on Bull Semen Parameters

Seminal parameters can be evaluated in situ, or samples can be delivered to a diagnostic centre. How storage conditions affect ejaculates up to evaluation is unclear. We assessed, in 25 commercial bulls electroejaculated in the field, the impact of time until evaluation (0-2 h, 4-6 h, and 24 h post-ejaculation), holding temperature (5 °C vs. room temperature), and extender (AndroMed^®, BIOXcell^® or INRA96^®) on semen quality. Acrosome integrity, sperm viability and morphology, CASA-total and progressive motility, pH, and colony-forming units were assessed. Semen quality was preserved for up to 4-6 h post-ejaculation, except for INRA96^® at 5 °C. Regardless of extender or temperature, motility decreased from 4 to 6 h up to 24 h, with the best values obtained with BIOXcell^® at 5 °C. pH differed from 4 to 6 h up to 24 h, acidifying when stored at room temperature. Microbiological load was stable over time with AndroMed^® and BIOXcell^®, and increased at room temperature with INRA96^®. Our results suggest that AndroMed^® and BIOXcell^® can preserve semen quality for up to 6 h, either at 5 °C or room temperature, while INRA96^® only at room temperature. These results help to fix adequate protocols for short-term storage and shipment of bovine semen collected under field conditions.

Evaluation of dextran for rabbit sperm cryopreservation: Effect on frozen-thawed rabbit sperm quality variables and reproductive performance

Effects were analysed of dextran supplementation to Me₂SO and acetamide rabbit semen freezing extenders on quality characteristics of rabbit spermatozoa and reproductive performance. The final concentration of cryoprotectants in pooled semen samples was 12.4 % Me₂SO for the A extenders, 10.7 % Me₂SO and 2.9 % acetamide for the D extenders and 8.9 % Me₂SO and 2.9 % acetamide in F extenders, with a supplementation of 1.7 % sucrose in all cases. There was not inclusion of dextran in the A0, D0, F0; while 5 % dextran was included in A5, D5, F5 and 10 % dextran in A10, D10 and F10 extenders. Sperm motility and viability rates were similar with use of the different extenders. Acrosome integrity after the freeze-thawing processes, however, was markedly greater when there was dextran supplementation of D and F extenders. Prolificacy was affected by extender composition. When there was artificial insemination (AI) using semen cryopreserved in the A extenders, number of kits born was similar to when there was AI with fresh semen when there was inclusion of 5% dextran for cryopreservation, while there was no effect on prolificacy when there was cryopreservation of semen using the D and F extenders. In conclusion, dextran supplementation of extenders containing Me₂SO and acetamide resulted in greater acrosome integrity. Furthermore, when there was AI using sperm preserved in cryo-diluents containing an intermediate concentration of Me₂SO, combined with inclusion of 5 % dextran, there was a marked beneficial effect on rabbit doe reproductive performance.

Genome-wide association studies for sperm traits in Assaf sheep breed

Sperm quality traits routinely collected by artificial insemination (AI) center for rams progeny test are related with the capacity to produce sperm doses for AI and, in more or less grade, with males' fertility. Low-quality ejaculates are unuseful to perform AI sperm doses, which suppose high economic loses for the AI center. Moreover, sperm quality traits have low heritability values which make traditional genetic selection little efficient to its improvement. In this work, a genome-wide association study (GWAS) was conducted by using sperm quality traits data and 50 K Affymetrix custom chip genotypes of 429 rams of Assaf breed from OVIGEN AI centre. Furthermore, 47 of these rams were also genotyped with the Illumina HD Ovine BeadChip, and therefore HD genotypes were imputed for all rams with phenotype data. Previous to the GWAS, a linear regression model was fitted including sperm traits as dependent variables; the flock of origin, date of sperm collection, and jump number as fixed effects; rams age at collection in months as covariate; and ram permanent effect as random. Pseudo-phenotypes obtained from this model were used as input for GWAS. Associations at the chromosome-wise level (FDR 10%) of 76 single-nucleotide polymorphisms (SNPs) in 4 chromosomes for ejaculate concentration (CON), 20 SNPs in 3 chromosomes for ejaculate volume (VOL), 32 SNPs in 1 chromosome for ejaculate number of spermatozoa (SPZ), and 23 SNPs for spermatozoa mass motility (MOT) in 17 chromosomes were found. Only SNPs associated with MOT overcame the genome-wide significance level. Some candidate genes for sperm traits variability were SLC9C1 (OAR1), TSN (OAR2), and FUT10 (OAR26) for MOT;. DOCK2, CPLANE1, SPEF2, and RAI14 (OAR16) for CON; SCAPER and PSMA4 (OAR18) for VOL; and PARM1 and LOC101110593 (OAR6) for SPZ. SNPs associated with sperm traits were not found to be correlated with milk production genetic variation; however, the high frequencies of some SNPs with negative effect over sperm traits found in animals at the top milk yield estimated breeding values (EBVs) ranking would allow to exert some selective presure to improve rams sperm performances. Effects and frequencies of some of the SNPs detected over sperm quality traits make these variants good candidates to be used in marker-assisted selection to improve sperm characteristics of Assaf rams and AI center efficiency to produce sperm doses.

Polyphenol-rich fraction of Alchornea cordifolia leaf ameliorates arsenite-induced infertility in male rats

Alchornea cordifolia is used traditionally for the treatment of infertility and venereal diseases. Thirty rats were randomly divided into five groups of six rats each: Group 1 (distilled water), group 2 (7 mg/kg sodium arsenite), group 3 (7 mg/kg sodium arsenite and 100 µg/kg polyphenol-rich fraction 1 of A. cordifolia), group 4 (7 mg/kg sodium arsenite + 100 µg/kg polyphenol-rich fraction 2) and group 5 (7 mg/kg sodium arsenite + α-tocopherol). The experiment lasted 30 consecutive days. Biochemical markers of oxidative stress and antioxidants, male reproductive hormones, spermatozoa function tests, histopathology, immunoreactivity of androgen receptor binding protein (ARBP) and anti-apoptotic B-cell lymphoma-2 protein expressions were estimated. Data were analysed using descriptive statistics and ANOVA at p < .05. Treatment with AF1 significantly decreased markers of oxidative stress, but increased the systemic antioxidants, testosterone, FSH, spermatozoa count and motility. Histopathological lesions of necrosis and germinal epithelial sloughing observed in sodium arsenite group were absent in sodium arsenite + 100 µg/kg polyphenol-rich fraction 1 group. Expressions of androgen receptor binding protein and anti-apoptotic B-cell lymphoma-2 were highest in sodium arsenite + 100 µg/kg polyphenol-rich fraction 1 group. In conclusion, the polyphenol-rich fraction of A. cordifolia is protective against sodium arsenite-induced infertility in male rats through the inhibition of oxidative and apoptotic mechanisms.

Stimulating effects of Quercetin (QUE) in tris citric acid extender on post thaw quality and in vivo fertility of buffalo (Bubalus bubalis) bull spermatozoa

Aim of this study was to evaluate the stimulating effects of quercetin (QUE) on post thaw quality and in vivo fertility of buffalo (Bubalus bubalis) bull spermatozoa. QUE is a well-known flavonoid having antioxidant properties to scavenge free radicals. Semen was collected from three buffalo bull through artificial vagina (42 °C) and were evaluated initially for volume, motility, concentration, followed by dilution in five extenders (n = 5 aliquots, control, C = no QUE; treatment 1, T1 = 50 μM QUE; treatment 2, T2 = 100 μM QUE; treatment 3, T3 = 150 μM QUE and treatment 4, T4 = 200 μM QUE supplementation). The experiment was repeated thrice (n = 3 replicates). At post dilution, sperm progressive motility (PM, %) plasma membrane integrity (PMI, %), supra vital plasma membrane integrity (SVPMI, %) and acrosome integrity (ACR-1, %) of buffalo bull were significantly higher (P < 0.05) in extenders supplemented with QUE than C. At thawing, sperm PM of buffalo bull was higher in T3 and T4 than C, T1 and T2. Sperm SVPMI was significantly higher in T2, T3 and T4 than C and T1. Sperm ACR-I was higher in T3 and T4 than C, T1 and T2. Sperm DNA integrity was higher in T4 than C. QUE supplementation increased in vitro semen quality during 30 and 60 min of incubation at 37 °C than C. The in vivo fertility was higher in T3 and T4 than C (%, 61.82 vs. 65.22 vs. 46.90). It is concluded that QUE @ 150 and 200 μM improved post thaw semen quality and in vivo fertility of buffalo bull.

Nanotechnology-based approach for safer enrichment of semen with best spermatozoa

BACKGROUND

Advances in nanotechnology have permitted molecular-based targeting of cells through safe and biocompatible magnetic nanoparticles (MNP). Their use to detect and remove damaged spermatozoa from semen doses could be of great interest. Here, MNP were synthesized and tested for their ability to target apoptotic (annexin V) and acrosome-reacted (lectin) boar spermatozoa, for high-throughout retrieval in a magnetic field (nanoselection). The potential impacts of nanoselection on sperm functions and performance of offspring sired by sperm subjected to nanoselection were determined. Fresh harvested and extended boar semen was mixed with various amounts (0, 87.5, and 175 μg) of MNP-conjugates (Annexin V-MNP or Lectin-MNP) and incubated (10 to 15 min) for 37 °C in Exp. 1. In Exp. 2, extended semen was mixed with optimal concentrations of MNP-conjugates and incubated (0, 30, 90, or 120 min). In Exp. 3, the synergistic effects of both MNP-conjugates (87.5 μg - 30 min) on spermatozoa was evaluated, followed by sperm fertility assessments through pregnancy of inseminated gilts and performance of neonatal offspring. Sperm motion, viability, and morphology characteristics were evaluated in all experiments.

RESULTS

Transmission electron microscopy, atomic force microscopy, and hyperspectral imaging techniques were used to confirm attachment of MNP-conjugates to damaged spermatozoa. The motility of nanoselected spermatozoa was improved (P < 0.05). The viability of boar sperm, as assessed by the abundance of reactive oxygen species and the integrity of the acrosome, plasma membrane, and mitochondrial membrane was not different between nanoselected and control spermatozoa. The fertility of gilts inseminated with control or nanoselected spermatozoa, as well as growth and health of their offspring were not different between (P > 0.05).

CONCLUSIONS

The findings revealed the benefit of magnetic nanoselection for high-throughput targeting of damaged sperm, for removal and rapid and effortless enrichment of semen doses with highly motile, viable, and fertile spermatozoa. Therefore, magnetic nanoselection for removal of abnormal spermatozoa from semen is a promising tool for improving fertility of males, particularly during periods, such as heat stress during the summer months.

Scrotal circumference: A predictor of testosterone concentration and certain attributes of seminal vesicles influencing buffalo male fertility

Aim:

The aim of this study was to evaluate the relationship of scrotal circumference (SC) with plasma testosterone, seminal vesicles (SVs) weight, and its secretion as measurable indicators of fertility and also to sequence and establish phylogenetic relatedness of certain SV protein genes with other species as such integrated approach is lacking.

Materials and Methods:

Altogether, 59 apparently healthy male buffaloes sacrificed at slaughterhouse were selected (irrespective of breed) for measuring SC and collecting blood and paired SVs. The SC was measured at greater curvature using soft thread. In the present study, blood plasma testosterone, cholesterol, protein, and glucose in addition to SV fructose, citric acid and proteins in SV fluid were also estimated. The SV tissue was fixed in RNAlater for RNA extraction. Male buffaloes were categorized as per total SV weight into Group I (<5.0 g), Group II (5.0-7.84 g), and Group III (>8.0 g) and dentitions-I (≤18 months), II (18-24 months), and III (≥24 months) to assess the effect of weight and dentition age on SC, SV weight, and its certain secretions. Data were analyzed using linear model procedure including Tukey HSD test and Pearson’s correlation coefficient. Variance inflation and condition index were also used to assess multicollinearity.

Results:

Gross and histomorphological evaluation of SVs did not show any abnormality. Macronutrients (plasma protein, glucose, and cholesterol) showed non-significant (p>0.05) variation between groups. The SC and SV weight varied significantly (p<0.05) with a significant positive relationship with plasma testosterone, SV protein, fructose, and citric acid. In addition, testosterone concentration also showed increasing trend from Groups I to III but increased significantly (p<0.05) from Group II to III with positive and significant correlations with SV protein, fructose, and citric acid similar to SV weight and SC. Binders of sperm protein (BSP1, 3, and 5) genes (full length) were sequenced and established an evolutionary relationship which is lacking in buffalo.

Conclusion:

The present findings established a significant positive correlation of SC with that of other fertility parameters related to SVs weight and its secretions: Fructose, citric acid, and protein (inclusive of BSPs sequenced full length), and testosterone. Therefore, the present integrated approach along with certain semen quality attributes reflecting epididymis function could be used as a predictive fertility marker for grading and selection of breeding bulls and their progenies to develop outstanding bull mother farm.

Effect of storage temperature, nitrogen gassing and sperm concentration on the in vitro semen quality and in vivo fertility of liquid bull semen stored in INRA96

The aim of this study was to assess the effect of storage temperature, nitrogen (N₂) gassing and sperm concentration on in vitro characteristics and calving rate (CR) following artificial insemination (AI) of liquid bull semen stored in INRA96. In Experiment 1 the effect of liquid bull semen diluted in either N₂ bubbled or non-bubbled INRA96 at a concentration of 5 × 10⁶ sperm per 0.25 mL insemination dose and stored at 5 or 15 °C was assessed subjectively for total and progressive motility on Days 0, 1, 2, 3 and 4 post collection. In Experiment 2a, the effect of stored liquid semen at three sperm concentrations (3, 4 or 5 × 10⁶ sperm per 0.25 mL insemination dose) on total and progressive motility was assessed subjectively on Days 0, 1 and 2 post collection. In Experiment 2b, the field fertility of liquid semen stored at ambient temperature at a concentration of 3, 4 or 5 × 10⁶ sperm per 0.25 mL dose and inseminated on Days 1 or 2 post collection was assessed in comparison to frozen-thawed semen (total of n = 5742). In Experiment 1, total and progressive motility decreased with increased duration of storage (P < 0.01); however, there was no effect of N₂ bubbling on motility on Days 0, 1, 2, 3 and 4 of storage. There was an effect of temperature on total and progressive motility, regardless of treatment, as semen stored at 15°C recorded higher motility values than semen stored at 5°C (P < 0.01). In Experiment 2a, there was no effect of sperm concentration on total or progressive motility on Days 0, 1 or 2 of storage. There was a linear decrease in motility with increased duration of storage (P < 0.01); however, there was no sperm concentration by day interaction. In Experiment 2b, there was an effect of sperm concentration on CR (P < 0.01); semen diluted to 3 and 4 × 10⁶ sperm per dose resulted in a lower CR after 2 days of storage (41.1 and 44.7%, respectively) in comparison to frozen-thawed semen (55.2%) but did not differ to CR of semen diluted to 5 × 10⁶ sperm per dose on Day 2 of storage. There was an effect of parity, fertility sub-index and days in milk (DIM) at AI on CR (P < 0.01). In conclusion, N₂ bubbling and sperm concentration had no effect on in vitro sperm motility of liquid semen, but this study demonstrated a reduction in CR on Day 2 of storage at lower sperm concentrations in comparison to frozen-thawed semen.

Sperm quality variables as indicators of bull fertility may be breed dependent

A means of discriminating among bulls of high fertility based on sperm quality is needed by breeding centers. The objective of the study was to examine parameters of sperm quality in bulls of known fertility to identify useful indicators of fertility. Frozen semen was available from bulls of known fertility (Viking Genetics, Skara, Sweden): Swedish Red (n=31), Holstein (n=25) and Others (one each of Charolais, Limousin, Blonde, SKB). After thawing, the sperm samples were analyzed for motility (computer assisted sperm analysis), plasma membrane integrity, chromatin integrity, acrosome status, mitochondrial activity and reactive oxygen species. A fertility index score based on the adjusted 56-day non-return rate for >1000 inseminations was available for each bull. Multivariate data analysis (Partial Least Squares Regression and Orthogonal Partial Least Squares Regression) was performed to identify variables related to fertility; Pearson univariate correlations were made on the parameters of interest. Breed of bull affected the relationship of sperm quality variables and fertility index score, as follows: Swedish Red: %DNA Fragmentation Index, r=-0.56, P<0.01; intact plasma membrane, r=0.40, P<0.05; membrane damaged, not acrosome reacted, r=-0.6, P<0.01; Linearity, r=0.37, P<0.05; there was a trend towards significance for Wobble, r=0.34, P=0.08. Holstein: Linearity was significant r=0.46, P<0.05; there was a trend towards significance for Wobble, r=0.45, P=0.08. In conclusion, breed has a greater effect on sperm quality than previously realized; different parameters of sperm quality are needed to indicate potential fertility in different breeds.

Novel agents for sperm purification, sorting, and imaging

The stringent selection of viable spermatozoa ensures the transmission of high-quality genetic material to the egg during fertilization. Sperm heterogeneity within or between ejaculates and between males obliges varied post-collection handling of semen to assure satisfactory fertility rates. The current techniques used to assess sperm generally detect non-viable and non-fertilizing gametes in the ejaculate, but do not permit the investigation of semen for improved fertility outcomes. Advances in technology, however, have spurred the search for new approaches to enrich semen with high-quality spermatozoa and to track intra-uterine sperm migration. This review highlights the current and future methodologies used for sperm labeling, selection, tracking, and imaging, with specific emphasis on the recent influence of nanotechnology.

Current status and potential of morphometric sperm analysis

The spermatozoon is the most diverse cell type known and this diversity is considered to reflect differences in sperm function. How the diversity in sperm morphology arose during speciation and what role the different specializations play in sperm function, however, remain incompletely characterized. This work reviews the hypotheses proposed to explain sperm morphological evolution, with a focus on some aspects of sperm morphometric evaluation; the ability of morphometrics to predict sperm cryoresistance and male fertility is also discussed. For this, the evaluation of patterns of change of sperm head morphometry throughout a process, instead of the study of the morphometric characteristics of the sperm head at different stages, allows a better identification of the males with different sperm cryoconservation ability. These new approaches, together with more studies employing a greater number of individuals, are needed to obtain novel results concerning the role of sperm morphometry on sperm function. Future studies should aim at understanding the causes of sperm design diversity and the mechanisms that generate them, giving increased attention to other sperm structures besides the sperm head. The implementation of scientific and technological advances could benefit the simultaneous examination of sperm phenotype and sperm function, demonstrating that sperm morphometry could be a useful tool for sperm assessment.

A Mouse Model for Dietary Xenosialitis: ANTIBODIES TO XENOGLYCAN CAN REDUCE FERTILITY

Humans can incorporate the xenoglycan N-glycolylneuraminic acid (Neu5Gc) from the diet into reproductive tissues and secretions. Most humans also have circulating antibodies specific for this dietary xenoglycan. The potential for inflammation induced by incorporated Neu5Gc and circulating anti-Neu5Gc antibodies, termed xenosialitis, has been discussed as a factor influencing several human diseases. Potential effects of xenosialitis on human fertility remain unknown. Here, we investigate possible adverse effects of the presence of Neu5Gc on sperm or endometrium combined with anti-Neu5Gc antibodies in semen or uterine secretions in a mouse model. We use Cmah(-/-) mice, humanized for Neu5Gc deficiency. We find that the viability, migration, and capacitation of sperm with incorporated Neu5Gc are negatively affected when these are exposed to anti-Neu5Gc antibodies. In addition, we find that after copulation, activated uterine neutrophils and macrophages show increased phagocytosis of sperm in the presence of anti-Neu5Gc antibodies via the complement receptor 3 (C3R) and Fcγ I/II/III (Fc receptor). Furthermore, Neu5Gc in endometrial cells combined with the presence of anti-Neu5Gc antibodies alters the receptivity and decidualization of endometrial explants. These studies provide mechanistic insights on how Neu5Gc on sperm and/or endometrium combined with anti-Neu5Gc antibodies in semen and uterine fluid might contribute to unexplained human infertility.

Variability in in vitro fertilization outcomes of prepubertal goat oocytes explained by basic semen analyses

This work analyses the changes that caprine spermatozoa undergo during in vitro fertilization (IVF) of in vitro matured prepubertal goat oocytes and their relationship with IVF outcome, in order to obtain an effective model that allows prediction of in vitro fertility on the basis of semen assessment. The evolution of several sperm parameters (motility, viability and acrosomal integrity) during IVF and their relationship with three IVF outcome criteria (total penetration, normal penetration and cleavage rates) were studied in a total of 56 IVF replicates. Moderate correlation coefficients between some sperm parameters and IVF outcome were observed. In addition, stepwise multiple regression analyses were conducted that considered three grouping of sperm parameters as potential explanatory variables of the three IVF outcome criteria. The proportion of IVF outcome variation that can be explained by the fitted models ranged from 0.62 to 0.86, depending upon the trait analysed and the variables considered. Seven out of 32 sperm parameters were selected as partial covariates in at least one of the nine multiple regression models. Among these, progressive sperm motility assessed immediately after swim-up, the percentage of dead sperm with intact acrosome and the incidence of acrosome reaction both determined just before the gamete co-culture, and finally the proportion of viable spermatozoa at 17 h post-insemination were the most frequently selected sperm parameters. Nevertheless, the predictive ability of these models must be confirmed in a larger sample size experiment.

A network-based method for the identification of putative genes related to infertility

BACKGROUND

Infertility has become one of the major health problems worldwide, with its incidence having risen markedly in recent decades. There is an urgent need to investigate the pathological mechanisms behind infertility and to design effective treatments. However, this is made difficult by the fact that various biological factors have been identified to be related to infertility, including genetic factors.

METHODS

A network-based method was established to identify new genes potentially related to infertility. A network constructed using human protein-protein interactions based on previously validated infertility-related genes enabled the identification of some novel candidate genes. These genes were then filtered by a permutation test and their functional and structural associations with infertility-related genes.

RESULTS

Our method identified 23 novel genes, which have strong functional and structural associations with previously validated infertility-related genes.

CONCLUSIONS

Substantial evidence indicates that the identified genes are strongly related to dysfunction of the four main biological processes of fertility: reproductive development and physiology, gametogenesis, meiosis and recombination, and hormone regulation.

GENERAL SIGNIFICANCE

The newly discovered genes may provide new directions for investigating infertility. This article is part of a Special Issue entitled "System Genetics" Guest Editor: Dr. Yudong Cai and Dr. Tao Huang.

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.

Assessment of motion and kinematic characteristics of frozen-thawed Sirohi goat semen using computer-assisted semen analysis

Aim:

The aim was to determine the motion and kinematics characteristic of frozen-thawed spermatozoa in Sirohi goat using computer-assisted semen analysis.

Materials and Methods:

A study was carried out in Sirohi buck. Semen collection was made biweekly from each buck with the help of artificial vagina. A total of 12 ejaculates were collected from two bucks (six ejaculates from each buck). Freshly collected semen was pooled and later evaluated. The pooled semen sample was extended with standard glycerolated egg yolk tris extender and later subjected to a process of cryopreservation. The motion and kinematic characteristics of spermatozoa were studied during freez-thawing process.

Results:

Significantly (p<0.01) higher value of live percent, hypo-osmotic swelling test, and acrosomal integrity were recorded in neat semen followed by diluted and frozen thaw semen. The proportion of spermatozoa showing slow progression were the highest in the neat and diluted semen followed by rapid and non-progressively motile, while a reverse pattern was observed in the frozen thaw semen where the proportion of non-progressively motile spermatozoa were significantly (p<0.01) higher followed by slow and rapid progression.

Conclusion:

This study showed that the best results for motion, vitality, plasma membrane integrity, and acrosome status were obtained in the neat semen followed by diluted and frozen thaw semen. Further, the process of cryopreservation results in a shift of motility from slow to non-progressive in the post-thaw semen with a significant decrease in the path velocities when compared to neat and diluted semen. Hence, it can be concluded that freezing-thawing process reduces the motility and kinematic characters spermatozoa and may be an important factor affecting the fertilizing ability of spermatozoa resulting in poor conception rate after insemination in goats.

Management and Breeding Soundness of Mature Bulls

Mature bulls must be fed a balanced ration, vaccinated appropriately, and undergo a breeding soundness evaluation to ensure they meet what is required of a short, but intense breeding season. To be classified as a satisfactory potential breeder, minimum standards for physical soundness, scrotal circumference, sperm motility, and sperm morphology must be achieved using an accepted bull-breeding soundness evaluation format. Sperm production requires approximately 70 days. Heat and stress are the most common insults to spermatogenesis, causing an increase in morphologic abnormalities with obesity-associated scrotal fat accumulation being the most frequent cause of elevated testicular temperature in mature bulls.

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.

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.

Feasibility of selection for male contribution to embryo survival as a way of improving male reproductive performance and semen quality in rabbits

The objective of this research was assess the male contribution to the number of implanted embryos (IE) and embryo survival (ES) estimated as the rate of variance due to male genetic and permanent environmental effects regarding total variance. In prolific species, the number of embryos and ES at early stages of gestation could be considered as fertility measurements because it indicates the number and rate of fertilized ova which are able to initiate the embryo development. Analyzed traits were ovulation rate (OR) estimated as the number of corpora lutea in both ovaries, IE estimated as the number of implantation sites, and ES calculated as IE/OR. A total of 1477 records from 900 females were used to analyze OR, whereas 1081 records from 855 females and 201 males were used to analyze IE and ES. The number of animals in the pedigree was 1107. The model included the systematic effects of year-season, parity order, lactation, and the random effects of additive genetics and permanent environmental effects due to the female (for OR) or both sexes (for IE and ES). Gibbs sampling was used to estimate posterior distributions of model parameters. The heritabilities of the male contribution to IE and ES were low (0.05 [0.01, 0.10] and 0.07 [0.02, 0.12]) but these estimates are probably biased downward since laparoscopy was only performed on those does that were pregnant at d 12 of gestation, instead of on all mated does. The genetic correlations between all analyzed traits and also between male and female genetic components of IE and ES were inaccurate, and it was not possible to draw any conclusion about them. The proportion of variation due to the male nonadditive genetic plus permanent environmental effects for IE and ES was almost negligible (0.027 [0.001, 0.058] and 0.031 [0.002, 0.068] for IE and ES, respectively), being the repeatability for male contribution on IE and ES around 8 and 10%, respectively.

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%).

Factors affecting the first service conception rate of cows in smallholder dairy farms in Bangladesh

The successful outcome of an insemination is a combination of both male and female fertility-linked factors. We investigated the first service conception rate of cows at artificial insemination (AI) in the smallholder dairy farms in Bangladesh. Frozen straws were prepared from ejaculates of Bos indicus (n = 7) and Bos indicus × Bos taurus (n = 7) AI bulls. Fertility was determined from 6101 first services in cows that were performed by 18 technicians in four regions between April 2004 and March 2005. Pregnancy was diagnosed by rectal palpation between 60 and 90 days post-insemination. The Asian version of Artificial Insemination Database Application (AIDA ASIA) was used for bulls-, cows- and AI-related data recording, and later retrieved for analysis. The mean ± SD number of inseminations performed from individual bulls and their conception rates were 436.0 ± 21.6 and 50.7 ± 1.9%, respectively. Logistic regression demonstrated body condition scores (BCS), heat detection signs, months of AI and their interactions had greatest effects (odds ratios: 1.24-16.65, p < 0.04-0.001) on first service conception rate in cows. Fertility differed (p < 0.02-0.001) between the regions, previous calving months, months of AI, BCS, parity and heat detection signs of cows. Inseminations based on mounting activity (n = 2352), genital discharge (n = 3263) and restlessness and/or other signs (n = 486) yielded a conception rate of 53.6%, 48.8% and 50.1%, respectively (p < 0.05). Conception rate between technicians ranged between 43.4% and 58.6% (p < 0.05). The days interval from calving to first service (overall mean ± SD = 153.4 ± 80.6) had relationship (p < 0.001) with BCS, months of previous calving and parity of the cows. Fertility at AI in smallholder farms can be improved by training farmers on nutrition and reproductive management of the cows.

Differential expression of cyclic-AMP responsive element modulator (CREM) mRNA isoforms during testicular development of boars

The cyclic-AMP responsive element modulator (CREM) transcription factor, a key regulator of spermatogenesis, can activate or repress gene expression by differential expression of alternatively spliced mRNA isoforms. The objective of this study was to report the sequences of the predominant CREM mRNA isoforms with leader exons B, θ1, θ2, in addition to the relative expression of these transcripts, in immature and adult boar testes. Activator CREM isoforms τγ (containing the B exon), θ1τγ and θ2τγ, were expressed in the adult boar testes, but not in immature testes. The CREM θ2τγ isoform had the highest expression levels in the adult boar testes compared to the τγ and θ1τγ isoforms (θ2τγ = 4.94 ± 1.49 in contrast to τγ = 1.66 ± 0.79 and θ1τγ = 2.32 ± 0.72; mean ± SD; P < 0.01). Interestingly, the predominant CREM mRNA isoforms in adult boar testes contained the C and γ exons; these exons are not present in human and rodent CREM mRNA, demonstrating species-specific expression. In contrast to the adult CREM isoforms, only CREM mRNA isoforms with the B exon (τ1 and α) were amplified in the 21 d (immature) boar testes. Further understanding of CREM mRNA isoform expression and regulation during boar spermatogenesis could contribute to our knowledge of spermatogenic efficiency in this species.

Sperm competition, sperm numbers and sperm quality in muroid rodents

Sperm competition favors increases in relative testes mass and production efficiency, and changes in sperm phenotype that result in faster swimming speeds. However, little is known about its effects on traits that contribute to determine the quality of a whole ejaculate (i.e., proportion of motile, viable, morphologically normal and acrosome intact sperm) and that are key determinants of fertilization success. Two competing hypotheses lead to alternative predictions: (a) sperm quantity and quality traits co-evolve under sperm competition because they play complementary roles in determining ejaculate's competitive ability, or (b) energetic constraints force trade-offs between traits depending on their relevance in providing a competitive advantage. We examined relationships between sperm competition levels, sperm quantity, and traits that determine ejaculate quality, in a comparative study of 18 rodent species using phylogenetically controlled analyses. Total sperm numbers were positively correlated to proportions of normal sperm, acrosome integrity and motile sperm; the latter three were also significantly related among themselves, suggesting no trade-offs between traits. In addition, testes mass corrected for body mass (i.e., relative testes mass), showed a strong association with sperm numbers, and positive significant associations with all sperm traits that determine ejaculate quality with the exception of live sperm. An "overall sperm quality" parameter obtained by principal component analysis (which explained 85% of the variance) was more strongly associated with relative testes mass than any individual quality trait. Overall sperm quality was as strongly associated with relative testes mass as sperm numbers. Thus, sperm quality traits improve under sperm competition in an integrated manner suggesting that a combination of all traits is what makes ejaculates more competitive. In evolutionary terms this implies that a complex network of genetic and developmental pathways underlying processes of sperm formation, maturation, transport in the female reproductive tract, and preparation for fertilization must all evolve in concert.

Mid-piece length of spermatozoa in different cattle breeds and its relationship to fertility

Recently positive correlation has been found between oxygen consumption (ZO2) in bull spermatozoa and non-return rates and concluded that an increase in ZO2, characteristic of the freeze/thaw process, was possibly associated with mitochondrial membrane damage during this procedure: alternatively, sperm may be hyperactivated through the capacitation-like effects of freezing/thawing. We speculated that the morphology of spermatozoa may be associated with their rate of ZO2 and fertility: for example, sperm mid-piece length where mitochondria are located. Such a relationship has not been investigated before, particularly in context of commercial cattle breeding programmes and bull fertility characteristics. Sperm biometry was performed on ejaculates obtained from 34 bulls representing six breeds: Holstein (yearlings and mature), Friesian, Belgian Blue, Aberdeen Angus, Charolais and Limousin. Five ejaculates were collected from every bull and from each sample a semen smear was fixed and stained with eosin/nigrosin: the mid-piece length of 40 sperm with normal morphology was measured in every sample. Data were analysed by breed, age and within each bull. Significant differences (p<0.01) between ejaculates in 9/34 bulls was found, as well as differences (p<0.001) between individual bulls within the same breed. The average mid-piece length for Aberdeen Angus was 13.35 microm, for Belgian Blues and Limousin around 13.8 microm and for Charolais 13.68 microm: for dairy breeds such as Holstein and Friesian it was about 13.4 microm. The mean value of mid-piece length for breed was compared with their 49 day non-return rate; a negative correlation (r = -0.53) was found in black and white dairy breeds.

The value of the percentage of motile sperm in predicting a significant portion of the fertility variation of frozen-thawed buck semen

Prediction of the future fertility of a given ejaculate with a simple laboratory test is still considered a real issue in domestic mammal breeding. This study showed that a subjective assessment of the percentage of motile spermatozoa, measured 120 min after thawing (mob120), can predict a significant part (∼50%) of the variation of the future fertility of buck ejaculates. The predictive model was calculated using a calibration data set composed of 40 ejaculates from four Alpine and six Saanen bucks. A fertility trial using split ejaculates was conducted in order to estimate ejaculate fertility. Taken into account were the herd within breed factor and the year, month, and inseminator factors. On average, one ejaculate was used to inseminate two females per herd in 10 different herds. This calibration set allowed us to choose the mob120 variable among a set of laboratory tests: mitochondrial activity, acrosomal status, membrane integrity, osmotic resistance test assessed by flow cytometry, velocity and motion characteristics assessed by computer-assisted sperm analysis, visually assessed percentage of motile, and motility score measured 5 and 120 min after thawing. For the calibration step, the best model used the logarithm of mob120 and gave a correlation coefficient of 0.71 between the field fertility and the predicted fertility and a standard error of 0.17. We tested this model on 3 different validation data sets adding up to 95 ejaculates that were all different from those of the calibration data set. The correlation coefficients between field fertility and predicted fertility were always significant and the bias corrected standard error ranged from 0.15 to 0.18 on these validation data sets. A Monte Carlo simulation showed that about 20% of the fertility variation remained to be explained.

Sperm morphology, motility and fertilisation capacity in the myobatrachid frog Crinia georgiana

Sperm traits have been found to vary between individuals within populations in a variety of taxa. Sperm motility, morphometry and viability may be expected to have important effects on male fertility, although previous studies have found varying patterns, especially in external fertilisers. In the present study, we examined the effects of sperm swimming velocity, the proportion of motile spermatozoa, sperm head and tail length and the proportion of live spermatozoa on fertilisation success in the externally fertilising myobatrachid frog Crinia georgiana using IVF techniques and by controlling sperm numbers. We found no effect of any of the sperm traits we measured on IVF success. Neither did we find any relationship between sperm morphology and sperm performance. There was a negative relationship between sperm viability and male body size, which could be a function of age or an alternative tactic of differential investment in spermatozoa by smaller-sized males using sneak tactics in multiple matings. In contrast with most externally fertilising aquatic organisms, high rates of fertilisation appear to be achieved in C. georgiana with relatively low sperm swimming speeds.

Semen molecular and cellular features: these parameters can reliably predict subsequent ART outcome in a goat model

Currently, the assessment of sperm function in a raw or processed semen sample is not able to reliably predict sperm ability to withstand freezing and thawing procedures and in vivo fertility and/or assisted reproductive biotechnologies (ART) outcome. The aim of the present study was to investigate which parameters among a battery of analyses could predict subsequent spermatozoa in vitro fertilization ability and hence blastocyst output in a goat model. Ejaculates were obtained by artificial vagina from 3 adult goats (Capra hircus) aged 2 years (A, B and C). In order to assess the predictive value of viability, computer assisted sperm analyzer (CASA) motility parameters and ATP intracellular concentration before and after thawing and of DNA integrity after thawing on subsequent embryo output after an in vitro fertility test, a logistic regression analysis was used. Individual differences in semen parameters were evident for semen viability after thawing and DNA integrity. Results of IVF test showed that spermatozoa collected from A and B lead to higher cleavage rates (0 < 0.01) and blastocysts output (p < 0.05) compared with C. Logistic regression analysis model explained a deviance of 72% (p < 0.0001), directly related with the mean percentage of rapid spermatozoa in fresh semen (p < 0.01), semen viability after thawing (p < 0.01), and with two of the three comet parameters considered, i.e tail DNA percentage and comet length (p < 0.0001). DNA integrity alone had a high predictive value on IVF outcome with frozen/thawed semen (deviance explained: 57%). The model proposed here represents one of the many possible ways to explain differences found in embryo output following IVF with different semen donors and may represent a useful tool to select the most suitable donors for semen cryopreservation.