Effect of semen preparation on casa motility results in cryopreserved bull spermatozoa

Ancillary Methods for Semen Evaluation

The cause of subfertility or poor fertility in naturally mated bulls should be differentiated from impotentia coeundi, generandi, or erigendi prior to ancillary semen evaluation. Bulls used for artificial insemination may undergo ancillary semen evaluation following low fertility rates as judged by poor conception or low pregnancy rates. Morphologically abnormal sperm have long been associated with bull subfertility and infertility. Some morphological defects such as improper sperm chromatin condensation are not visible using traditional light microscopy and require specialized staining. Ancillary semen evaluation is useful in cases where the reason for low or absence of fertility needs to be identified. As compared to SEM, TEM can be extremely useful for identifying minuscule acrosome defects, issues with chromatin, and centrosome defects and is considered the gold standard method for the identification of midpiece and tail defects.

Influence of the coincubation of post-thawed bull semen with elevated β-hydroxybutyrate concentrations on sperm characteristics

In this study, the relationships between post-thaw bull sperm characteristics and hyperketonemic conditions after coincubation with cow plasma or media were determined to investigate if such a condition could affect bull sperm characteristics. Two experiments were conducted. In experiment 1, blood samples were collected from 31 cows to prepare plasma. Cows were independently categorized into two groups according to plasma β-hydroxybutyrate (BHB) concentrations (above or below 1.2 mM). Thawed bull semen was diluted and incubated with diluted plasma; motility parameters were evaluated using Computer Assisted Semen Analysis (CASA). In experiment 2, a pooled sample of thawed semen was diluted and divided into three aliquots: without BHB (control) and treated with either 1.2 mM (1.2) or 3 mM (3) BHB. In addition to motility, flow cytometric analyses were carried out. In experiment 1, the overall motility decreased significantly in plasma containing high (≥1.2 mM) BHB compared to plasma containing low (<1.2 mM) BHB. In experiment 2, the overall motility tended to be lower in BHB (3 mM)-supplemented samples. The supplementation of 3 mM BHB increased the proportion of live superoxide-positive sperm and sperm with high mitochondrial potential, while the DNA fragmentation index decreased.

Bull Semen Obtained on Beef Farms by Electroejaculation: Sperm Quality in the First Two Hours of Storing with Different Extenders and Holding Temperatures

Sperm quality decreases over time, so bull semen may need to be preserved after field collection. However, the effect of handling such semen samples from commercial farms and placing them in very short-term storage has not been elucidated. Therefore, ejaculate from 25 bulls from 1 dairy and 14 beef cattle farms were collected under farm conditions and evaluated for semen quality during the first two hours after collection. Two commercial extenders (AndroMed^® and BIOXcell^®) and two different storage temperatures (5 °C and room temperature) were used to evaluate the influence on semen quality and sperm kinetics in ejaculates grouped into three evaluation times, based on time since collection (Time 1: <75 min, n = 7; Time 2: 75-105 min, n = 11; and Time 3: 105-120 min, n = 7). Classical semen parameters, sperm motion kinetics by CASA and colony-forming units were assessed. The differences between both extenders in curvilinear and straight-line velocities (VCL and VSL) for the different time groups (Time 2 and Time 3) were statistically significant for p < 0.05. AndroMed^® showed lower VSL, straightness and linearity in sperm compared to BIOXcell^® (p < 0.05). In conclusion, AndroMed^® induced more curvilinear movement, while BIOXcell^® stimulated straighter motility.

Effect of modified CEP-3 diluents with aqueous soybean extract on liquid semen quality in Ongole crossbred bull

Background and Aim

Egg yolk (EY) is commonly used as an extracellular cryoprotectant in semen diluents but has some negative effects. Therefore, this study aimed to assess the potential of lecithin derived from plants, such as soybeans, as an alternative extracellular cryoprotectant and to characterize liquid semen quality of Ongole crossbred bulls using a modified caudal epididymis plasma-3 [CEP-3 (m)] as a base diluent and aqueous soybean extract (ASE).

Materials and Methods

A bull with progressive motility (PM) of fresh semen >70% was used. Two soybean extracts were also used, namely, ASE 1 and ASE 2, obtained by extraction procedures 1 and 2, respectively. The study was conducted using an experimental design with 11 treatments and ten replications, with diluents comprising different levels of ASE 1 and ASE 2, as well as a positive control with 10% EY. The parameters measured were motility (M) and its kinetic parameters, including PM, M, velocity curve linear, velocity straight linear, velocity average pathway, linearity, straightness, wobble, amplitude lateral head beat cross frequency, and hyperactivity using computer-assisted sperm analysis, viability, and spermatozoa abnormalities.

Results

The CEP-3(m) diluent formula and ASE 1 at a 30% level maintained the PM of spermatozoa up to day 5 (40.7% ± 16.1%) of cold storage. Meanwhile, the CEP-3(m) diluent formula and ASE 2 could only maintain PM >40% until day 3 (42.1% ± 13.5%) of cold storage at a 30% level. The CEP-3(m) diluent and ASE 1 at a level of 25%-30% supported spermatozoa life (viability) up to day 5 with a value >80% (81.8 ± 3.5; 86.4 ± 2.6). The abnormality value of spermatozoa in various diluents during cold storage on days 0-5 was below 20%.

Conclusion

Soybean extracts 1 and 2 can substitute EYs as extracellular cryoprotectants in modified CEP-3 basic diluents. Soybean extract 1 can support the life of spermatozoa up to day 5 but may cause the viscosity and movement of spermatozoa to be hyperactive. Soybean extract 2 can support the life of spermatozoa up to the 3rd day of cold storage and produces progressive (non-rotating) movement patterns. Further, research is recommended with higher levels of ASE 2.

The sperm mitochondria: clues and challenges

Sperm cells rely on different substrates to fulfil thei energy demand for different functions and diverse moments of their life. Species specific mechanism involve both energy substrate transport and their utilization: hexose transporters, a protein family of facilitative passive transporters of glucose and other hexose, have been identified in spermatozoa of different species and, within the species, their localization has been identified and, in some cases, linked to specific glycilitic enzyme presence. The catabolism of hexose sources for energy purposes has been studied in various species, and recent advances has been made in the knowledge of metabolic strategies of sperm cells. In particular, the importance of aerobic metabolism has been defined and described in horse, boar and even mouse spermatozoa; bull sperm cells demonstrate to have a good adaptability and capacity to switch between glycolysis and oxidative phosphorylation; finally, dog sperm cells have been demonstrated to have a great plasticity in energy metabolism management, being also able to activate the anabolic pathway of glycogen syntesis. In conclusion, the study of energy management and mitochondrial function in spermatozoa of different specie furnishes important base knowledge to define new media for preservation as well as newbases for reproductive biotechnologies.

Growth performance, reproductive parameters and fertility measures in young Nellore bulls with divergent feed efficiency

The growth, sexual maturity and fertility-related parameters related of young Nellore bulls with divergent residual feed intake (RFI) raised on pasture were evaluated. After classification of 48 young males as low and high RFI (more and less efficient, respectively), the animals were evaluated for growth and reproductive parameters at 28-day intervals from 14.3 to 24.6 months of age. The semen was cryopreserved in the last sampling and fresh and post-thaw semen samples were evaluated. Low RFI bulls exhibited higher initial and final body weight (P < 0.05), but feed intake, body condition score and growth measures evaluated by carcass ultrasound were unaffected by RFI (P > 0.05). The scrotal circumference, sperm concentration, defects, and quality of fresh semen, and ultrasonographic testicular characteristics were unaffected by RFI (P > 0.05). However, velocity parameters such as average path and curvilinear velocities determined by computer-assisted sperm analysis of thawed semen submitted to the rapid thermoresistance test were improved (P < 0.05) in low RFI bulls, but this improvement in quality did not enhance in vitro sperm fertilizing ability. Our results demonstrated significant differences in metabolism and growth performance between bulls of divergent RFI. In addition, there was slight improvement in the semen quality of bulls with low RFI bulls, but this did not enhance in vitro fertilizing ability. Selection of beef bulls for RFI can be performed, which will result in economic benefits by improving the growth performance of the animals without affecting reproductive parameters.

An evidence of Humanin-like peptide and Humanin mediated cryosurvival of spermatozoa in buffalo bulls

Buffalo spermatozoa are vulnerable to cryo-injuries due to inherent deficiency of endogenous antioxidants, high polyunsaturated fatty acids (PUFA) content in plasma membrane and low cholesterol/phospholipid (C/P) ratio. Humanin is a potent cytoprotective agent that protects the cells against oxidative stress and apoptosis. The present study was designed to establish the presence of Humanin in buffalo and effect of Humanin supplementation on freezability of buffalo spermatozoa. Indirect immunofluorescence test revealed presence of Humanin in ejaculated and epididymal spermatozoa, and, elongated spermatids and interstitial space in the testicular tissue section. Humanin levels in seminal plasma were significantly and positively correlated with sperm concentration and individual progressive motility (IPM) in good (n = 22; IPM >70%) and poor (n = 10; IPM <50%) quality ejaculates. For supplementation studies, a total of 24 ejaculates (IPM ≥70%) were collected and each ejaculate was then divided into four aliquots. First aliquot was diluted with egg yolk-tris-glycerol (EYTG) extender without Humanin and served as control group (Group I). Rest three aliquots were diluted with extender containing 2 (Group II), 5 (Group III) and 10 μM Humanin (Group IV), respectively. Semen was cryopreserved using standard protocol and evaluated at pre-freeze for lipid peroxidation (LPO) and post-thaw stages for spermatozoa kinematics, LPO, mitochondrial membrane potential (MMP), capacitation, apoptotic status and DNA integrity. The treatment group that showed best results (5 μM) was compared with control group for in vitro fertility assessment by homologous zona binding assay. The LPO levels were lower (p < 0.05) in 5 and 10 μM Humanin supplemented group. The MMP and DNA integrity were higher (p < 0.05) in 5 μM group than other groups. F-pattern was higher (p < 0.05) and B-pattern was lower (p < 0.05) in 5 and 10 μM Humanin supplemented groups. Lower apoptotic and higher viable spermatozoa (p < 0.05) were observed in 5 μM Humanin group. The mean number of spermatozoa bound to zona pellucida was higher (p < 0.05) in 5 μM Humanin treated group than the control group. The study established the presence of Humanin in buffalo spermatozoa and seminal plasma for very first time and concluded that Humanin supplementation at 5 μM concentration improves the freezability and in vitro fertility of buffalo spermatozoa.

High-Efficiency Bovine Sperm Sexing Used Magnetic-Activated Cell Sorting by Coupling scFv Antibodies Specific to Y-Chromosome-Bearing Sperm on Magnetic Microbeads

Sperm sexing technique is favored in the dairy industry. This research focuses on the efficiency of bovine sperm sexing using magnetic-activated cell sorting (MACS) by scFv antibody against Y-chromosome-bearing sperm (Y-scFv) coupled to magnetic microbeads and its effects on kinematic variables, sperm quality, and X/Y-sperm ratio. In this study, the optimal concentration of Y-scFv antibody coupling to the surface of magnetic microbeads was 2–4 mg/mL. PY-microbeads revealed significantly enriched Y-chromosome-bearing sperm (Y-sperm) in the eluted fraction (78.01–81.43%) and X-chromosome-bearing sperm (X-sperm) in the supernatant fraction (79.04–82.65%). The quality of frozen–thawed sexed sperm was analyzed by CASA and imaging flow cytometer, which showed that PY-microbeads did not have a negative effect on X-sperm motility, viability, or acrosome integrity. However, sexed Y-sperm had significantly decreased motility and viability. The X/Y-sperm ratio was determined using an imaging flow cytometer and real-time PCR. PY-microbeads produced sperm with up to 82.65% X-sperm in the X-enriched fraction and up to 81.43% Y-sperm in the Y-enriched fraction. Bovine sperm sexing by PY-microbeads showed high efficiency in separating Y-sperm from X-sperm and acceptable sperm quality. This initial technique is feasible for bovine sperm sexing, which increases the number of heifers in dairy herds while lowering production expenses.

Evaluation of Semen Quality of Jeju Black Cattle (JBC) to Select Bulls Optimal for Breeding and Establish Freezing Conditions Suitable for JBC Sperm

Simple Summary

Jeju black cattle, a type of native Korean cattle characterized by black fur covering the entire body, inhabit Jeju Special Self-Governing Province, a World Natural Heritage Site. Although this breed was state designated as a natural monument in 2013 due to its characteristics and genetic traits, it is on the verge of extinction and thus there is a need to preserve this breed and further improve its traits. Therefore, we evaluated sperm motility, vitality, and morphology, which have long been considered good predictors of fertility in the absence of female infertility factors. Our findings showed that the semen of the JBC-A bull was superior to the semen of four other JBC bulls. Due to the aging of the population of JBC breeding bulls, strategies should be devised to improve sperm production in vivo.

Abstract

To optimize the reproduction of Jeju black cattle (JBC), freezing conditions for sperm were established and sperm motility, vitality, morphology, and fertility were evaluated to select the optimal bull for breeding. Semen samples from five JBC bulls were individually mixed with freezing medium at a final concentration of 1 × 108 sperm/mL and frozen in liquid nitrogen vapor at a height of 3 or 7 cm (referred to as 3 cm sperm and 7 cm sperm, respectively). When the freezing conditions were compared, the motility of 7 cm sperm was significantly higher than that of 3 cm sperm for the JBC-A bull. The motility, curvilinear velocity, straight-line velocity, and average path velocity of fresh and frozen–thawed sperm were the highest for the JBC-A bull. The vitalities of fresh and frozen–thawed sperm were the highest for the JBC-A/E and JBC-A bulls, respectively. The percentage of normal cells in fresh sperm was the highest for the JBC-D bull. The rates of the normal formation of two pronuclei and total sperm penetration were the highest in zygotes fertilized with sperm from the JBC-A bull. The sperm from the JBC-A bull had superior qualities and are thus the most appropriate choice for the preservation and reproduction of these endangered cattle.

Zearalenone interferes with the sperm-triggered inflammation in the bovine uterus in vitro: Negative impact on sperm motility and survival

Zearalenone (ZEN)-contaminated diets induce detrimental effects on the bovine reproduction. Recently, we reported that active sperm induce pro-inflammatory responses in bovine endometrial epithelial cells (BEECs) in vitro. This study aimed to investigate the impact of presence of ZEN on the sperm-uterine crosstalk in vitro. BEECs monolayers were stimulated by ZEN (10, 100, and 1000 ng/mL) for 0, 3, 6, 12, or 24 h and gene expressions were analyzed by real-time PCR. Moreover, BEECs were pre-exposed to ZEN (10, 100, and 1000 ng/mL) for 24 h then, co-incubated with sperm for 6 h. Conditioned media (CM) from a sperm-BEECs co-culture, after pre-exposure to ZEN, were harvested and exploited to challenge either polymorphonuclear cells (PMNs) or sperm. Both PMNs phagocytic activity toward sperm and sperm motility parameters were then assessed. Results showed that ZEN alone induced pro-inflammatory responses in BEECs through the induction of mRNA expressions of pro-inflammatory cytokines (TNFA and IL1B) and PGES1 at different time points. Pre-exposure of BEECs to ZEN, amplified the sperm-triggered upregulation of pro-inflammatory cytokines (TNFA and IL1B) and chemokine IL8 mRNA abundance in BEECs. Sperm-BEECs conditioned media, primed by ZEN, stimulated the PMNs phagocytosis for sperm whereas suppressed sperm motility parameters. Taken together, these findings indicate that the presence of ZEN augments the pro-inflammatory cascade triggered by sperm in BEECs, provokes PMNs phagocytosis for sperm, and reduces sperm motility parameters. Such immunological reactions may create a hostile environment for sperm competence and survival in the bovine uterus, thus impair fertility.

Computer-assisted sperm analysis (CASA) in veterinary science: A review

Computer-assisted sperm analysis (CASA) allows an assessment of sperm motion and morphology more accurately and objectively than by subjective evaluation. Although, CASA instruments have improved significantly during last 40 years especially in terms of software, image capture and computer settings, little has changed regarding processes for analyzing sperm motion attributes. The main problem is related to validation, consistency and optimization of equipment and procedures. Differences among CASA systems denote problems of objective analysis of results between different semen processing units. If validated, CASA systems can provide a great tool to objectively compare sperm motility and morphology. Sperm motility is one of the indicators most evaluated before and after cryopreservation vis-à-vis quality and fertilizing ability. Researchers have determined a possible relationship of CASA outputs with bull fertility in vivo; however, a clear association has not yet been confirmed. Most CASA measures depend upon concentration, sample volume, type of extender, duration of analysis and thawing temperature. For each attribute, CASA software should provide outputs based on a range rather than means or medians for transformed data. The current review describes development, validation requirements, limitations and future expansions associated with CASA technology.

Seminal attributes of Vechur bulls (Bos indicus), the smallest humped dairy cattle

The study was undertaken at Mattupatti semen station to objectively evaluate the seminal attributes of frozenthawed semen of Vechur bulls, the smallest humped dairy cattle in the world, using the computer assisted semen analyzer (CASA) and Flow cytometer. The mean motility and progressive motility of the frozen-thawed semenestimated via CASA was 77.25±9.56 and 64.0±4.21% respectively. Mean values obtained for the sperm kinetic parameters like path velocity (VAP), progressive velocity (VSL), track speed (VCL), lateral head amplitude (ALH),beat cross frequency (BCF), straightness (STR) and linearity (LIN) were 82.56±12.12, 76.22±10.38, 107.77±21.42, 4.39±0.91, 20.87±3.81, 92.37±3.25 and 72.87±6.64% respectively. Flow cytometry analysis of the functional sperm parameters like sperm viability, live sperms with intact acrosome, sperms with normal mitochondrial membranepotential (MMP) and sperms with altered DNA were 81.67±4.55, 76.16±9.76, 82.40±5.61 and 11.75±0.3% respectively. The mean value of the HOS reactive sperms was 71.81±5.71%. Mean values for the length and width of the sperm head, length of mid-piece, tail and overall sperm length measured by computer image analysis was 8.99±0.36, 5.07±0.23, 14.21±0.35, 45.12±1.53 and 68.32±1.41 μm respectively. Study concluded that seminal attributes of Vechur bulls could be estimated with CASA and Flow cytometer and the parameters were comparable to other indigenous, crossbreds and exotic dairy cattle.

A Combined Flow Cytometric Semen Analysis and miRNA Profiling as a Tool to Discriminate Between High- and Low-Fertility Bulls

Predicting bull fertility is one of the main challenges for the dairy breeding industry and artificial insemination (AI) centers. Semen evaluation performed in the AI center is not fully reliable to determine the level of bull fertility. Spermatozoa are rich in active miRNA. Specific sperm-borne miRNAs can be linked to fertility. The aim of our study is to propose a combined flow cytometric analysis and miRNA profiling of semen bulls with different fertility to identify markers that can be potentially used for the prediction of field fertility. Sperm functions were analyzed in frozen-thawed semen doses (CG: control group) and high-quality sperm (HQS) fraction collected from bulls with different field fertility levels (estimated relative conception rate or ERCR) by using advanced techniques, such as the computer-assisted semen analysis system, flow cytometry, and small RNA-sequencing. Fertility groups differ for total and progressive motility and in the abnormality degree of the chromatin structure (P < 0.05). A backward, stepwise, multiple regression analysis was applied to define a model with high relation between in vivo (e.g., ERCR) and in vitro (i.e., semen quality and DE-miRNA) fertility data. The analysis produced two models that accounted for more than 78% of the variation of ERCR (CG: R² = 0.88; HQS: R² = 0.78), identifying a suitable combination of parameters useful to predict bull fertility. The predictive equation on CG samples included eight variables: four kinetic parameters and four DNA integrity indicators. For the HQS fraction, the predictive equation included five variables: three kinetic parameters and two DNA integrity indicators. A significant relationship was observed between real and predicted fertility in CG (R² = 0.88) and HQS fraction (R² = 0.82). We identified 15 differentially expressed miRNAs between high- and low-fertility bulls, nine of which are known (miR-2285n, miR-378, miR-423-3p, miR-191, miR-2904, miR-378c, miR-431, miR-486, miR-2478) while the remaining are novel. The multidimensional preference analysis model partially separates bulls according to their fertility, clustering three semen quality variable groups relative to motility, DNA integrity, and viability. A positive association between field fertility, semen quality parameters, and specific miRNAs was revealed. The integrated approach could provide a model for bull selection in AI centers, increasing the reproductive efficiency of livestock.

Efficiency of three boar sperm enrichment techniques

The objective of the study was to investigate the efficiency of three enrichment methods to separate boar spermatozoa. Twenty-four ejaculates from 12 boars (2 ejaculates/boar) were extended (30 × 10⁶ spermatozoa/mL) in commercial Beltsville Thawing Solution. Each semen sample was processed with glass wool column (GW) and glass beads (GB) filtration and with the single-layer centrifugation (SLC) technique. Semen samples before (control; C) and after treatment were evaluated for sperm CASA motility/kinetics and concentration, viability, morphology and chromatin integrity. Data were analysed with mixed models. The concentration of total and motile spermatozoa was significantly decreased after treatment in groups GW and SLC, but not in group GB. Group GW showed increased values of WOB compared with both groups C and GB. Group GB showed greater values of rapid movement spermatozoa and lower values of slow movement spermatozoa compared with group C. In group SLC, higher values of VSL, LIN and STR were observed compared with group C. In conclusion, all techniques under examination enhanced various CASA variables. Based on our results, the GB method is a promising alternative separation technique for boar sperm and deserves further research regarding swine in vitro fertilization.

Sperm motility, kinematics, morphometry and morphology over two seasons in free-ranging African elephants (Loxodonta africana)

This study aimed to address the lack of information on quantitative semen and sperm characteristics of free-ranging African elephants. Nineteen ejaculates were collected from 12 elephant bulls by means of electroejaculation in spring (Season 1, end of dry season, n=7) and in autumn (Season 2, end of rainy season, n=12). While most elephant cows are in oestrus in the rainy season, it is not evident whether sperm quality also improves during this period. Semen samples were assessed using computer-aided sperm analysis (CASA), brightfield microscopy and transmission electron microscopy. Seasonal differences and individual variation in sperm quality of bulls were apparent, with ejaculates collected during Season 2 revealing higher percentages for total motility, progressive motility, rapid-swimming spermatozoa and kinematic parameters compared with Season 1 (P<0.05). Although normal sperm morphology percentage was similar over the two seasons, more sperm tail defects were found in Season 2 (P<0.05). The baseline reference data and multivariate sperm parameter associations reported in this study can be used to predict elephant bull sperm quality and potential to fertilise. It is clear that CASA can detect subtle differences in sperm quality of African elephant ejaculates and should be the approach for future investigations.

Comparison of commercially available chamber slides for computer-aided analysis of human sperm

Despite the increasing use of computer-aided sperm analysis (CASA) in clinical practice, there is still no golden standard for the type of slide to be used with these systems. Counting chamber depth and loading method, can profoundly influence motility and concentration estimates, thereby undermining the validity and accuracy of CASA. To contribute toward standardized sperm analysis, this study compared different commercially available capillary-filled slides including 10 and 20 µm deep Leja slides (Leja10 and Leja20); 10, 16 and 20 µm deep CellVision slides (CV10, CV16 and CV20); and drop-loaded slides including slide and coverslip (SCS) with a depth of 20.1 µm and the Makler chamber with a depth of 10 µm for sperm analysis when using CASA. The Sperm Class Analyzer (SCA) CASA system was used to assess concentration, motility, and detailed kinematic parameters of 20 normozoospermic human samples using the different chamber slides. Results were evaluated by the repeated measures ANOVA and Intraclass correlation coefficients. The Makler chamber showed significantly (P < 0.05) higher concentrations than other slides. However, there was no significant difference in the percentage of sperm in different motility groups among the slides. CV10, Leja10 and Makler showed significantly higher curvilinear-, average path- and straight-line velocity (VCL, VAP, VSL) values than other slides. In conclusion, despite the objectiveness of the assessments by CASA systems, there are still some discrepancies in the results of sperm concentration, motility and other kinematic parameters when using different commercially available slides. The possible negative influence of the sperm quality misdiagnosis on the selection of treatment strategy in a clinical setting, emphasizes the need for further standardization and quality control of the commercially available chamber slides for use with CASA. Furthermore, this study found more consistent results for capillary-filled chambers compared to drop-loaded slides, suggesting a superior method when using CASA.Abbreviations: DNA: Deoxyribonucleic acid; CASA: Computer-aided semen analysis; SCA: Sperm Class Analyzer; WHO: World Health Organization; CV: CellVision; SCS: Slide and Coverslip; SD: Standard deviation; ANOVA: Analysis of Variance; PR: Progressive; NP: Non-progressive; IMT: Immotile; VCL: Curvilinear velocity; VAP: Average path velocity; VSL: Straight-line velocity; Lin: Linearity; STR: Straightness; WOB: Wobble; ALH: Amplitude of lateral head displacement; BCF: Beat cross frequency.

Optimization of CASA-Mot Analysis of Donkey Sperm: Optimum Frame Rate and Values of Kinematic Variables for Different Counting Chamber and Fields

Simple Summary

A reliable sperm motility exam is important for semen analysis and breeding soundness examination. Different parameters can affect the Computer Assisted Sperm Analysis (CASA) motility results. Today, new high-resolution cameras and different chambers are introduced to CASA systems, and protocol optimization is required to render the estimation results for donkey sperm. The objective of this study is the optimization of the conditions used for donkey semen motility analysis with CASA-Mot by defining the optimum frame rate for different chamber types. Additionally, to study the effect of different chamber types, chamber field and sperm dilution on the sperm kinematic parameters with higher frame rates are examined.

Abstract

In order to optimize the donkey sperm motility analysis by the CASA (Computer Assisted Sperm Analysis)-Mot system, twelve ejaculates were collected from six jackasses. Capillary loaded chamber (CLC), ISAS^®D4C depths 10 and 20 µm, ISAS^®D4C Leja 20 and drop displacement chamber (DDC), Spermtrack^® (Spk) depths 10 and 20 µm were used. Sperm kinematic variables were evaluated using each chamber and a high-resolution camera capable of capturing a maximum of 500 frames/second (fps). The optimum frame rate (OFR) (defined according to curvilinear velocity—VCL) was dependent on chamber type. The highest OFR obtained was 278.46 fps by Spk20. Values for VCL, straight-line velocity (VSL), straightness (STR), amplitude of lateral head displacement (ALH) and beat cross frequency (BCF) were high in DDC and 10 µm depth. In both DDC 10 and 20 µm, the sperm velocities (VCL, VSL, VAP) and ALH values decreased significantly from the centre to the edges, while Wobble and BCF increased. No defined behavior was observed along the CLC. However, all the kinematic variables had a higher value in a highly concentrated sample, in both chamber types. In conclusion, analyzing a minimum of nine fields at 250 fps from the centre to the edges in Spk10 chamber using a dilution of 30 × 10⁶ sperm/mL offers the best choice for donkey computerised sperm motility analysis.

The Effect of Resorcinol on Bovine Spermatozoa Parameters in Vitro

The goal of this study was to observe the effect of resorcinol on motility, viability and morphology of bovine spermatozoa. The semen was used from six randomly chosen breeding bulls. Ejaculate was diluted by different solutions of resorcinol in 1:40 ratio. Samples were divided into 7 groups with different concentrations of resorcinol (Control, RES1 - 4 mg/ml, RES2 - 2 mg/ml, RES3 - 1 mg/ml, RES4 - 0.5 mg/ml, RES5 - 0.25 mg/ml and RES6 - 0.125 mg/ml). Motility of spermatozoa was detected using CASA method at temperature of 37 °C in time periods 0, 1, 2, 3, 4 hours from the start of the experiment. Significant motility differences between all groups except control and RES6 with difference of 5.58 %, as well as between RES1 and RES2 groups with difference of 2.17 % were found. Progressive motility had the same significant differences. Spermatozoa viability (MTT test) decreased compared to control in all experimental groups during the entire duration of experiment. Observing morphologically changed spermatozoa, no significant changes were observed and a higher percentage of spermatozoa with separated flagellum in all experimental resorcinol groups compared to control were detected. Also, increased number of spermatozoa with broken flagellum, acrosomal changes and other morphological forms in the group with the highest concentration of resorcinol (RES1) were found. Results of our study clearly show negative effects on motility parameters of spermatozoa which depend on concentration, cultivation temperature and time period.

Padronização do Sperm Class Analyzer® (SCA®) para avaliação de espermatozoides equinos criopreservados

RESUMO Objetivou-se, no primeiro experimento, avaliar o efeito da velocidade de captura de imagens de 25Hz, 30Hz e 50Hz na cinética dos espermatozoides equinos criopreservados. Todas as velocidades mostraram-se adequadas para capturar o movimento espermático (P>0,05). No segundo experimento, objetivou-se avaliar o efeito da deposição de sêmen em lâmina sob lamínula, Leja®10 e 20, na cinética espermática. O uso de lâmina e lamínula foi superior às lejas para manter a LIN e o WOB (P<0,05). No terceiro experimento, objetivou-se avaliar o efeito das concentrações de 25, 50 e 100x106 na cinética espermática. As concentrações de 25 e 50 x106 foram superiores a 100x106 para preservar a LIN, a STR e a BCF e não afetar negativamente a motilidade (P<0,05). No quarto experimento, objetivou-se avaliar o efeito dos diluidores BotuCrio®, BotuSêmen®, TALP sperm e da solução fisiológica na cinética espermática. O BotuCrio® foi superior a todos os diluidores em preservar a BCF e os hiperativos (P<0,05). Conclui-se que o emprego da velocidade de captura entre 25 e 50Hz, a deposição do sêmen entre lâmina e lamínula e a rediluição em diluidor de congelação para atingir 25 a 50x106 de espermatozoides/mL são ideais para o SCA® avaliar, de forma fidedigna, o sêmen equino criopreservado.

Different approaches for assessing sperm function

Different approaches can be used to assess sperm function in different conditions, i.e. sperm storage, freezing-thawing or activation by induction of capacitation and acrosome reaction. In this review we will focus on the assays routinely performed in our laboratories, giving a literature support to critically analyse different approaches. In fact, researchers usually tend to look for the "one shot" parameter that could explain itself a specific process; it is our conviction that a multiparametric approach is still more valid, as some changes in sperm function are very complex and could be explained only by operating in different ways. Sperm motility, the most evident sperm characteristic, should be assessed by computer-aided sperm analysers that permit an objective evaluation of the motility and its kinematic parameters. Commercial and open source instruments are available and could be profitably used together with specific statistical approaches. The use of microscopy, and particularly fluorescent microscopy, could be a very useful tool to assess different parameters in sperm cells both by fluorophores that give indication of a determined function, and by immunolocalization of proteins, that permits the discover of new features or to explain particular sperm functions. The same substrates could be used also in flow cytometry: the difference is that it permits to study wider sperm populations (and their sub-population distribution). Flow cytometry is undergoing a very wide use in spermatology and technical and experimental rigor is needed to obtain reliable results. Metabolic assessment of sperm features, particularly energetic supply, ATP formation and other enzyme activities, could represent a very important challenge to acquire new information and complete/integrate those derived from other techniques. Finally, functional assays such as oocyte binding and in vitro fertilization, represent a very strong tool to assess sperm function in vitro, as they could evidence the functional intactness of some pathways.

Effectiveness of tes-tris or tris association with low density lipoprotein on in vitro longevity of refrigerated buffalo semen

ABSTRACT This study investigated in vitro the efficacy of four different extenders (TES-TRIS and TRIS with LDL low-density lipoprotein at concentrations of 10 or 5%) on the longevity of buffalo sperm in the refrigeration process at 5ºC. Sperm motility was assessed every 24 hours up to 72 hours of incubation using computer assisted sperm analysis and sperm membrane integrity was examined by the hypoosmotic test (HOST) at T1, T24, T48 and T72 hours. Eleven buffaloes (1 ejaculate per buffalo) of the Murrah breed were used, ranging in age from 4 to 5 years. Immediately after collection, each ejaculate was fractionated into 4 aliquots, and each aliquot was diluted in one of four diluents to obtain 50x106SPTZ/mL. The samples were packed in 0.5mL straws and refrigerated (-0.25°C/min) to 5°C and maintained at this temperature until evaluation. Prior to evaluation the samples were heated at 37°C for 30 seconds. The statistical package used for analysis was STATA 12.0 "Statistical Analysis Software" and means were compared by the Friedman test (P<0.05). The results of sperm kinetics and HOST indicate that the TRIS diluent with 10% LDL could be a promising alternative for semen refrigeration at 5ºC, to be used in conventional and fixed time artificial insemination.

Semen analysis and sperm characteristics of Karan Fries cattle

Karan Fries is an Indian composite breed of cattle with superior milk production with a greater disease resistance than many other cattle. Understanding of the basic sperm and semen characteristics is necessary to develop the artificial insemination and sperm sexing methods. This study was conducted to evaluate the morphological, rheological and biochemical characteristics of Karan Fries (Indian composite breed) bull semen. Semen analysis was conducted using Computer Assisted Sperm Analysis (CASA) and rheological methods. Results from correlation assessments indicated there was a positive correlation among values for sperm velocity variables. Motility of bull sperm movements in a linear path were the important variables evaluated in this study. There was also characterization of the individual spermatozoa using scanning electron microscopy (SEM) and Raman spectroscopy. The sperm head length and width were 8.8 ± 0.8 and 3.9 ± 0.6 μm, respectively, and the approximate flagellum length was 59.4 ± 4.5 μm. There was a difference in the Raman intensity among the individual spermatozoa. Results of this study could be important in designing and developing methods of artificial insemination, cryopreservation of semen and semen sexing.

CASA-Mot in mammals: an update

Sperm motility is one of the most widely used parameters of sperm quality. Computer-aided sperm motility analysis (CASA-Mot) systems were developed to reduce the subjectivity of sperm motility assessment, and have had broad scientific and practical acceptance. In this review, the sources of variation and current applications of this technology and its relationships with other sperm quality tests are described in detail. Despite remarkable advances in the technique, there is still great need for standardisation in many species, and the numerous factors that affect the results make it difficult to provide universally accepted criteria for classifying semen samples based on sperm motility characteristics. The main fields for CASA-Mot include the study of male fertility and pathologies, evaluation of the effects of physical and chemical agents, improvement of epidemiological survey studies, more precise calculation of seminal doses for farm animals, realisation of basic studies about sperm function, improvement of sperm technologies such as cryopreservation and quality control analysis. Numerous relationships have been established between CASA-Mot and other sperm quality tests, although most of these parameters are complementary. Future CASA-Mot systems will probably be able to integrate several sperm quality parameters with motility.

Combined effects of type and depth of counting chamber, and rate of image frame capture, on bull sperm motility and kinematics

Semen quality assessment requires accurate, reliable and objective methods for examination of sperm variables including sperm motility. For preparation of semen samples for artificial insemination, as a genetic resource, samples that are used for insemination need to have the capacity to result in a highly acceptable fertility rate. Several methods have been developed for evaluation of bull sperm in laboratory conditions and for preparation of doses for artificial insemination. Computer-assisted semen analyses can provide objective information on various sperm variables. Nevertheless, this equipment requires fine-calibrations considering differences among species, breeds and conditions for sample evaluation and data analyses. In the present study, there was examination of the interaction between factors such as image frame rate and type and depth of counting chamber in which sperm were evaluated, together with differences between bulls of four breeds. The use of the Spermtrack® reusable 10 μm-depth chamber provided more reliable results than results obtained using disposable chambers (10 and 20 μm depth). A capture rate of at least 90 fps is required for assessment of sperm motility percentage, whereas a rate of 250 fps is needed for obtaining consistent kinematic data. Differences among breeds in the present study indicate conditions for sperm analyses should include specific equipment calibrations for each breed. These results contribute to development of more precise conditions for assessments of bull sperm quality taking into account breed differences and the requirement each breed has for the adequate evaluation and preparation of samples for artificial insemination.

Sexual maturity and fertility-related measures in young Nellore bulls receiving long-term dietary supplementation with rumen-protected polyunsaturated fatty acids

The objective of this study was to evaluate the effects of long-term supplementation with rumen-protected fatty acids (FA) on growth and reproductive parameters of young Nellore bulls in a grazing regime. Forty-eight young bulls were distributed into two groups: FA (supplemented with rumen-protected polyunsaturated FA); and control (control fat-free supplement). The animals were supplemented from 14.3 to 24.6 months of age and growth and reproductive parameters were evaluated at 28-day intervals. The semen was cryopreserved in the last collection and fresh and post-thaw semen samples were evaluated. Feeding FA did not affect (P > 0.05) growth, reproductive parameters (scrotal circumference, sperm concentration per mL of ejaculate, percentage of sperm defects, sperm quality and fertility in vitro), or testicular ultrasonographic characteristics. However, thawed semen from bulls fed FA exhibited better quality (P < 0.05) than control semen for the following parameters evaluated by computer-assisted sperm analysis: average path velocity [μm/s: 90.48 vs. 79.66 post-thaw and 74.81 vs. 72.80 post-rapid thermoresistance test (TRT)], straight-line velocity (μm/s: 72.37 vs. 65.20 post-thaw and 64.96 vs. 63.25 post-TRT), and curvilinear velocity (μm/s: 148.44 vs. 131.31 post-thaw and 115.68 vs. 113.35 post-TRT). In addition, feeding FA increased peripheral concentrations of testosterone, leptin, total cholesterol and high-density lipoprotein. In conclusion, the increase in testosterone concentrations in bulls fed FA was not related to variations in growth parameters and sexual maturity. In addition, post-thawing sperm velocities were enhanced by diet, however, such increases were not related to better in vitro embryo production rates.

High-throughput characterisation of bull semen motility using differential dynamic microscopy

We report a high-throughput technique for characterising the motility of spermatozoa using differential dynamic microscopy. A movie with large field of view (∼10mm2) records thousands of cells (e.g. ≈ 5000 cells even at a low cell density of 20 × 106 cells/ml) at once and yields averaged measurements of the mean ([Formula: see text]) and standard deviation (σ) of the swimming speed, head oscillation amplitude (A0) and frequency (f0), and the fraction of motile spermatozoa (α). Interestingly, we found that the measurement of α is facilitated because the swimming spermatozoa enhance the motion of the non-swimming population. We demonstrate the ease and rapidity of our method by performing on-farm characterisation of bull spermatozoa motility, and validate the technique by comparing laboratory measurements with tracking. Our results confirm the long-standing theoretical prediction that [Formula: see text] for swimming spermatozoa.

Combined effect of type and capture area of counting chamber and diluent on Holstein bull sperm kinematics

The evaluation of sperm motion is crucial for processing of seminal doses for artificial insemination. Here, the combined effect of the type and capture area of three counting chambers, together with the type of diluent employed, on sperm motility was analysed. Ejaculates from thirteen Holstein bulls were used for sperm kinematic analysis with the ISAS^® v1 CASA-Mot system, using two capillary-loaded counting chambers (Leja^® and Cell-Vu^® ) and one drop displacement chamber (Makler^® ). Nine fixed positions were analysed per chamber type, considering central and lateral and three longitudinal fields. Independent of the diluent used, differences were found between the three chambers. Independent of the extender, no differences in x-axis were observed with Cell-Vu^® , while using Leja^® , some parameters showed lower values in the centre than in lateral areas. In both counting chambers, the lowest values were observed in the distal area. Results obtained with the two diluents were highly different with a very low correlation between them. In conclusion, the capture area inside the chambers leads to significant changes in sperm kinematic parameters and different dilution media introduce considerable differences in the motility patterns. It is necessary to optimise sampling methods and specific set-ups to be used with CASA-Mot technology.

Relationship between post-thaw adenosine triphosphate content, motility and viability in cryopreserved bovine semen applying two different preservation methods

Motility and energy level in sperm cells are tightly linked, but not totally understood. The aim of this study was to examine whether adenosine triphosphate (ATP) content as a sperm quality parameter for bull semen could give additional information together with viability and motility. The objective was therefore to examine the relationships between alterations in sperm ATP content, motility and viability in bovine semen samples immediately after thawing and following post-thaw incubation at physiological temperature. Two different cryopreservation methods were compared. Ejaculates from ten young bulls were split into two and cryopreserved using conventional procedure with Biladyl^® (B) extender and with SpermVital^® (SV) immobilization technology. From each sample, simultaneous analysis of ATP content, motility and viability was performed post-thaw (T0) and after incubation at physiological temperature for three hours (T3). Multivariate correlation analysis showed high correlation at T0 between ATP content and viability (p < 0.05), ATP and total motility (p < 0.05), as well as progressive motility and viability (p < 0.05). However, there was no significant correlation between progressive motility and ATP content at T3, neither for B nor SV semen. We conclude that both preservation method and post-thaw incubation at physiological temperature affect ATP level in bull sperm cells partly independent of motility and viability. The ATP level of bovine spermatozoa post-thaw is therefore implicated to give supplementary information of sperm quality.

CASA-Mot technology: how results are affected by the frame rate and counting chamber

For over 30 years, CASA-Mot technology has been used for kinematic analysis of sperm motility in different mammalian species, but insufficient attention has been paid to the technical limitations of commercial computer-aided sperm analysis (CASA) systems. Counting chamber type and frame rate are two of the most important aspects to be taken into account. Counting chambers can be disposable or reusable, with different depths. In human semen analysis, reusable chambers with a depth of 10µm are the most frequently used, whereas for most farm animal species it is more common to use disposable chambers with a depth of 20µm . The frame rate was previously limited by the hardware, although changes in the number of images collected could lead to significant variations in some kinematic parameters, mainly in curvilinear velocity (VCL). A frame rate of 60 frames s-1 is widely considered to be the minimum necessary for satisfactory results. However, the frame rate is species specific and must be defined in each experimental condition. In conclusion, we show that the optimal combination of frame rate and counting chamber type and depth should be defined for each species and experimental condition in order to obtain reliable results.

Pulse wave Doppler ultrasound of testicular arteries and their relationship with semen characteristics in healthy bulls

BACKGROUND

Semen evaluation is used to estimate the testicular function. In bulls, the spermatozoa present in the ejaculate are the result of a process that begun more than 2 mo earlier, bequeathing a delayed depiction of the actual function of the testis. Since testis vascularization might be critical for the gonad function, selected pulse wave Doppler ultrasound parameters were assessed in this study, for instance the peak systolic velocity, the end diastolic velocity and the resistive index of the testicular artery along the spermatic cord, the marginal portion of the testicular artery and the intratesticular branches of the testicular artery both in healthy adult and young bulls. Correlations between these parameters and characteristics of semen that was collected numerous times, before and after the Doppler ultrasound examination.

RESULTS

The peak systolic velocity and the end diastolic velocity measured in the testicular artery along the spermatic cord (supratesticular artery - SA) were variable among the bulls and within individual bulls, likely due to the convoluted course of the vessel. The resistive index was found highly repeatable in the same bull. A reduction in the resistive index was found between the supratesticular artery and the marginal portion of the testicular artery (P < 0.01), and between the marginal portion of the testicular artery and the intratesticular branches of the testicular artery (P < 0.05). No differences were recorded for the pulse wave Doppler ultrasound parameters in young bulls compared with adults. A significant correlation was found between the resistive index of the marginal portion of the testicular artery and total sperm in the ejaculate (r = 0.516, P < 0.05), the immature sperm (r = 0.462, P < 0.05), the teratoid sperm (r = 0.375, P < 0.05), and the "Dag defect" sperm (r = 0.389, P < 0.05). Similarly, the resistive index of the intratesticular branches of the testicular artery were found correlated with the total sperm number in the ejaculate (r = 0.568, P < 0.05), the immature sperm (r = 0.523, P < 0.05), the teratoid sperm (r = 0.418, P < 0.05), and the "Dag defect" sperm (r = 0.341, P < 0.05).

CONCLUSIONS

The data presented in this study suggest that the resistive index, measured at the marginal portion of the testicular artery, could be an easy-to-perform parameter to evaluate the spermatogenesis quality in young bulls and normal adults.

Evaluation of sperm motility with CASA-Mot: which factors may influence our measurements?

Computer-aided sperm analysis (CASA) is now routinely used in IVF clinics, animal breeding centres and research laboratories. Although CASA provides a more objective way to evaluate sperm parameters, a significant number of factors can affect these measurements. This paper classifies these factors into four categories: (1) sample and slide (e.g. preincubation time, type of specimen and type of chamber slide); (2) microscope (e.g. light source and microscope stage); (3) hardware and software, including the settings of each system; and (4) user-related factors. We review the effects of the different factors in each category on the measurements made and emphasise the need to take measures to standardise evaluations. The take-home message of the present article is that there are several commercial and useful CASA systems, and all are appropriate for routine analysis. Non-commercial systems may also be good choices when the user needs to adapt the device to specific experimental conditions. In both cases (commercial and non-commercial), it is important that standard protocols are put in place for evaluation, as well as methods to validate the system.

Factors affecting staining to discriminate between bull sperm with greater and lesser mitochondrial membrane potential

The sperm mitochondrial membrane potential (MMP) is usually evaluated using the JC-1 dye. This study aimed to verify the effect of incubation temperature (25 °C or 38 °C), incubation time (10, 30, and 45 min), JC-1 stain concentration (0.2 μM, 2 μM, 8 μM, 12 μM), and the presence of glycerol (6.6% compared with 0%), on the capacity of the stain to discriminate between sperm with high mitochondrial membrane potential (hMMP) and low mitochondrial membrane potential (lMMP) in fresh and frozen bull sample by both flow cytometry and epifluorescence microscopy. The temperature (38 °C for 10 min) and the dye concentration (8 μM and 12 μM) resulted in a greater proportion of hMMP (P < .05). The incubation for 45 min at 38 °C resulted in a significant reduction of hMMP in samples stained with JC-1 dye at 8 μM and 12 μM (P < .01). A longer incubation time (45 min) and greater dye concentration (8 μM and 12 μM) resulted in an increased proportion of hMMP sperm in cryopreserved samples. Fresh sperm incubated with glycerol had a hMMP (P < .05). Data for the present study indicate that the optimal incubation temperature was 38 °C, with an incubation time differing between fresh (10-30 min) and cryopreserved sperm (at least 45 min). Furthermore, the JC-1 dye concentration used that could reliably detect the proportion of hMMP sperm was 2 μM in fresh samples, and at least 8 μM in cryopreserved sperm.

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.

Protective effect of crocetin on bovine spermatozoa against oxidative stress during in vitro fertilization

Oxidative stress is one of the major factors that contribute to poor semen quality and low rates of in vitro fertilization. Crocetin, a main constituent of saffron (Crocus sativus L.) possesses potent antioxidant activity, by scavenging reactive oxygen species (ROS) and/or enhancing the activity of intracellular antioxidant enzymes. The aim of this study was to investigate, for the first time, the effect of crocetin on the quality characteristics of bull spermatozoa and fertilization rate. For this reason, frozen/thawed bovine spermatozoa were incubated with crocetin (1, 2.5, and 5 μm), for 120 or 240 min, in the presence of a negative control, and evaluated in terms of motility, viability, acrosomal status, DNA fragmentation index, intracellular ROS, and lipid peroxidation. In order to evaluate the impact of crocetin on cleavage and blastocyst rate, the compound was added in the IVF medium at the previously identified optimal concentration (2.5 μm). The results indicate that incubation of spermatozoa with 2.5 μm of crocetin resulted in a statistically significant lower production of superoxide anion and hydrogen peroxide, lower lipid peroxidation, and in better maintenance of motility parameters, viability, and acrosomal integrity, with a very small number of cells with DNA fragmentation, compared to the other groups (p < 0.05). The presence of crocetin (2.5 μm) in the fertilization medium also resulted in a significant increase in acrosome-reacted spermatozoa and blastocyst production, compared to the control group (p < 0.01). These data indicate that crocetin (2.5 μm) positively affects bovine sperm quality characteristics during a 240-min incubation and improves its fertilizing ability, directly and/or indirectly, by regulating ROS concentration and lipid peroxidation.

Single and double layer centrifugation improve the quality of cryopreserved bovine sperm from poor quality ejaculates

Background

Density gradient centrifugation was reported as a technique of semen preparation in assisted reproductive techniques in humans and animals. This technique was found to be efficient in improving semen quality after harmful techniques such as cryopreservation. Recently a modified technique, single layer centrifugation, was proposed as a technique providing a large amount of high quality spermatozoa, and this treatment was performed before conservation. Single layer centrifugation has been studied prevalently in stallions and in boars, but limited data were available for bulls. Occasionally bulls are known to experience a transient reduction in semen quality, thus techniques that allow improvement in semen quality could be applied in this context. The aim of this study was the evaluation of single layer and double layer centrifugation by the use of iodixanol, compared with conventional centrifugation and non-centrifuged semen, on the sperm characteristics during the cryopreservation process in bulls with normal and poor semen quality.

Results

Single layer centrifugation and double layer centrifugation both significantly increased the percentage of normal spermatozoa and decreased the percentage of non-sperm cells in poor quality samples, while both were ineffective in those of normal quality. Sperm characteristics in poor quality samples increased after single layer centrifugation and double layer centrifugation, reaching values similar to those recorded in normal samples, and this trend is maintained after equilibration and after cryopreservation. On the other hand, SLC and DLC resulted in a consistent reduction in the spermatozoa recovered, and this resulted in a reduction of the absolute amount of spermatozoa cryopreserved in the normal samples, without a clear improvement in sperm characteristics in this type of sample.

Conclusions

These data suggested that both SLC and DLC could be performed in practice, but their application should be limited to the cases in which the quality of the spermatozoa recovered is more important than the total amount of spermatozoa.

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.

Influence of chamber type integrated with computer-assisted semen analysis (CASA) system on the results of boar semen evaluation

The objective of the study was to evaluate the effect of different types of chambers used in computer-assisted semen analysis (CASA) on boar sperm concentration and motility parameters. CASA measurements were performed on 45 ejaculates by comparing three commonly used chambers: Leja chamber (LJ), Makler chamber (MK) and microscopic slide-coverslip (SL). Concentration results obtained with CASA were verified by manual counting on a Bürker hemocytometer (BH). No significant differences were found between the concentrations determined with BH vs. LJ and SL, whereas higher (p<0.01) values of this parameter were obtained with MK. Compared to MK and SL, significantly higher values were recorded in LJ for velocity (VCL and VAP) as well as amplitude of the lateral head displacement (ALH) and beat cross frequency (BCF), which was associated with significantly higher percentages of motile, progressively motile and rapidly progressive motile spermatozoa. Higher values for the linearity (LIN) and straightness (STR) of sperm movement were obtained for the analysis performed in MK and SL. In both these chambers, the results of all the linearity and kinetic parameters of sperm were similar (p>0.05). The results obtained show that CASA assessment of boar semen should account for the effect of counting chamber on the results of sperm motility and concentration, which confirms the need for further study on standardizing the automatic analysis of boar semen.