The relationship of increased susceptibility of sperm DNA to denaturation and fertility in the stallion

Proteomic analysis of sperm from fertile stallions and subfertile stallions due to impaired acrosomal exocytosis

Thoroughbred stallions that carry a double-homozygous genotype A/A-A/A for SNPs rs397316122 and rs69101140 in exon 5 of the FKBP6 gene (chr13; EquCab3.0) are uniquely subfertile due to impaired acrosomal exocytosis (IAE). In this study, the sperm proteome in frozen/thawed semen from subfertile Thoroughbred stallions was studied and compared to that of frozen/thawed sperm from fertile Thoroughbred stallions. A total of 2,220 proteins was identified, of which 140 proteins were found to be differentially abundant in sperm from the subfertile stallions compared to that of fertile stallions (83 less and 57 more abundant). Proteins of differential abundance in sperm from the subfertile stallions were mainly overrepresented in the "metabolism" and the "metabolism of lipids" pathways. One of these proteins, arylsulfatase F (ARSF), was studied by immunofluorescence. A lower proportion of sperm displaying ARSF signal at the acrosome region was observed in sperm from subfertile Thoroughbred stallions. In addition, heterologous zona pellucida binding assays revealed that sperm from subfertile Thoroughbred stallions bound at a lower proportion to zonae pellucidae than sperm from fertile Thoroughbred stallions. In conclusion, a group of differential abundance proteins, including some of acrosome origin, were identified in sperm from subfertile stallions with acrosome dysfunction.

Quercetin in semen extender improves frozen-thawed spermatozoa quality and in-vivo fertility in crossbred Kamori goats

This study investigated the antioxidant effect of quercetin-treated semen on frozen-thawed spermatozoa quality and in-vivo fertility in crossbred Kamori goats. In total, 32 ejaculates from four fertile bucks were diluted in Tris-based egg yolk extender with varying levels of quercetin (0, 1, 5, 10, and 15 μM). Qualified semen samples were pooled and frozen in French straws. The results revealed that the addition of quercetin in the semen extender increased (p < 0.05) frozen-thawed sperm total motility (TM), progressive motility (PM), rapid velocity (RV), average path velocity (VAP), straight line velocity (VSL), curvilinear velocity (VCL), and amplitude of lateral head (ALH) displacement in contrast to the control group. Quercetin supplementation had no effect on beat cross frequency (BCF), straightness (STR), and linearity (LIN) (p > 0.05). Quercetin showed significantly higher (p < 0.05) plasma membrane and acrosome integrity and viability (p < 0.05) of spermatozoa in contrast to the control group. Quercetin in the semen extender significantly increased (p < 0.05) superoxide dismutase (SOD), catalase (CAT), peroxidase (POD), ascorbate peroxidase (APX), and total antioxidant capacity (TAC) levels while reduced (p < 0.05) the contents of total oxidant status (TOS) and malondialdehyde (MDA), which were in contrast to the control group. Ultrasound results revealed that 24 out of 30 (80%) goats were found pregnant when semen was treated with 5 μM quercetin while the control group showed 18 out of 30 (60%) animals were pregnant. Thus, the study concluded that 5 μM quercetin-treated semen was found to be efficient, showed increased antioxidant status, and reduced oxidant production, leading to improved spermatozoa quality and in-vivo fertility in goats.

Factors affecting the success of laparoscopic artificial insemination in sheep

Successful artificial breeding underpins rapid genetic and production gains in animal agriculture. In sheep, artificial insemination with frozen semen is performed via intrauterine laparoscopy as frozen-thawed spermatozoa do not traverse the cervix in sufficient numbers for high fertility and transcervical insemination is anatomically impossible in most ewes. Historically, laparoscopic artificial insemination has always been considered reasonably successful, but recent anecdotal reports of poor fertility place it at risk of warning adoption. Understanding the male, female and environmental factors that influence the fertility of sheep is warranted if the success of artificial insemination is to be improved and genetic progress maximised for the sheep industry. This review details the current practice of laparoscopic AI in sheep. It explores the effects of semen quantity and quality, the ewe, her preparation, and environmental conditions, on the fertility obtained following laparoscopic artificial insemination.

Factors affecting the analysis and interpretation of sperm quality in frozen/thawed stallion semen

In the current study, we examined: 1) the agreement (bias) between fluorescence-based methods (NucleoCounter-SP100 [NC] vs. flow cytometry [FC]) for determining the viability (VIAB) of frozen/thawed stallion sperm; 2) the agreement between post-thaw sperm total motility (TMOT) and VIAB; 3) whether a difference between TMOT and VIAB [VIAB - TMOT] in frozen/thawed stallion sperm could be explained by the level of lipid peroxidation in viable sperm (VLPP); 4) the repeatability of post-thaw analysis of sperm quality; and 5) the effect of final post-thaw semen dilution (10, 30, or 50 x 106 sperm/mL) on sperm motion characteristics. Post-thaw VIAB was similar between NC and FC (P > 0.05), and the agreement between these two methods was high (bias: 1 to -3). The agreement between post-thaw TMOT and VIAB decreased as the pre-freeze percentages of morphologically normal sperm and DNA quality decreased: bias - 4 to - 25. The bias between [VIAB - TMOT] and VLPP ranged from - 5 to 7. Differences in post-thaw sperm quality (TMOT, PMOT, VIAB, and sperm concentration) were not observed when analyzing one or three straws per ejaculate (P > 0.05). There was no effect of post-thaw sperm concentration (i.e., 10 vs. 30 vs. 50 x 106 sperm/mL) on sperm motion characteristics (P > 0.05). This study reports factors other than post-thaw sperm motility that warrant further consideration when analyzing frozen/thawed stallion sperm.

Comparison of two processing techniques on the sperm quality of semen contaminated with urine

Urospermia in stallions can occur intermittently, consistently, or as an isolated event, and may result in reduced sperm quality which is often assumed to reduce fertility. Although sperm quality declines in urospermic ejaculates, fertility has not been assessed in mares bred with urine contaminated semen. The aims of this study were to compare sperm quality after simple dilution (SD), cushioned centrifugation (CC) alone, or cushioned centrifugation combined with a 40 % silane-coated silica solution (SC) in semen contaminated with 0, 20, or 40 % (v/v) urine. Sperm quality values tended to decrease as the percent urine increased within all treatments (SD, CC, SC) after 24 h of cooled storage. However, SC treated groups had higher sperm quality compared to SD and CC when exposed to 20 or 40 % (v/v) urine. Differences in pregnancy rates among treatment groups (SD with 0 or 40 % (v/v) urine, or 40 % (v/v) urine followed by SC) were unable to be detected.

Lactate-induced spontaneous acrosomal exocytosis as a method to study acrosome function in stallion sperm

Evaluation of acrosome function in stallion sperm is mostly based on the use of inducers of acrosomal exocytosis (AE), such as the calcium ionophore A23187 or progesterone. Recently, it has been reported that incubation of stallion sperm under presumed capacitating conditions (i.e., medium formulated with calcium, bicarbonate, and bovine serum albumin) using a lactate-only containing medium (Lac-MW) results in a high rate of spontaneous AE in viable sperm (AE/Viable). In the current study, we developed an alternative assay of acrosome function for stallion sperm following the incubation of sperm in a medium formulated only with lactate as an energy substrate (Lac-MW). In Experiment 1, freshly ejaculated stallion sperm was incubated with 10 μM A23187, Lac-MW, or Control, for up to 6 h under capacitating conditions. The percentages of motile sperm, viable sperm, total AE (Total AE), and AE in viable sperm (AE/Viable) were compared among treatment groups. Incubation in Lac-MW, but not with Control or A23187, resulted in a time-dependent increase in the percentage of AE/Viable, as determined by flow cytometry, particularly at 4 and 6 h of incubation (P < 0.05). In Experiment 2, freshly ejaculated sperm was incubated in Lac-MW for up to 6 h, and the occurrence of protein tyrosine phosphorylation and AE/Viable were determined. At 4h and 6h of incubation in Lac-MW, ∼40% of the sperm displayed a protein tyrosine phosphorylation immunofluorescence pattern that coincides with that recently associated with stallion sperm capacitation (i.e., immunofluorescence signal at the acrosome and midpiece). In Experiment 3, the rate of AE/Viable sperm was compared among freshly ejaculated, cool-stored, and frozen/thawed stallion sperm. Except at 2h incubation in Lac-MW, differences in mean AE/Viable among fresh, cool-stored, and frozen/thawed sperm were not observed (P > 0.05). In Experiment 4, the relationship between Total AE (A23187), or AE/Viable (Lac-MW), and in vivo fertility of 5 stallions was determined. A linear relationship was observed between mean AE/Viable and the per-cycle (r = 0.93; P < 0.05) and seasonal (r = 0.66; P < 0.05) pregnancy rates of five stallions used for artificial insemination with cool-stored semen. In Experiment 5, frozen/thawed sperm from subfertile Thoroughbred (TB) stallions, known to carry the susceptibility genotype for Impaired Acrosomal Exocytosis (IAE; FKBP6 A/A-A/A) was evaluated following incubation in Lac-MW. Sperm from subfertile TB stallions with IAE had lower mean AE/Viable, at both 4h and 6h incubation in Lac-MW, when compared to that of fertile control stallions (P < 0.05). Overall, the Lac-MW model validated in the current study may be a useful complementary assay to evaluate the ability of stallion sperm to physiologically undergo AE and to study stallion fertility potential. This acrosome function assay can be used to evaluate fresh, cool-stored, or frozen/thawed stallion sperm, and describes a strong linear relationship with in vivo-fertility of stallions used in artificial insemination programs.

Deciphering sperm chromatin properties to predict stallion sperm fertility

Although previous studies have examined the relationship between the sperm DNA fragmentation index and fertility in stallions, other aspects of chromatin structure or packaging and fertility have not been explored. In the present study, relationships between fertility and DNA fragmentation index, protamine deficiency, total thiols, free thiols and disulfide bonds in stallion spermatozoa were investigated. Ejaculates (n = 36) were collected from 12 stallions and extended to prepare semen doses for insemination. One dose from each ejaculate was sent to the Swedish University of Agricultural Sciences. Aliquots of semen were stained for flow cytometry with acridine orange for the Sperm Chromatin Structure Assay (DNA fragmentation Index, %DFI), with chromomycin A3 (CMA) for protamine deficiency, and with monobromobimane (mBBr) for detection of total and free thiols and disulfide bonds. Per season pregnancy rates after insemination were obtained. Mixed linear models were used to analyze data. Negative correlations were found between pregnancy rate and %DFI (r = -0.35, P < 0.03) and pregnancy rate and free thiols (r = -0.60, P < 0.0001). Furthermore, there were positive correlations between total thiols and disulfide bonds (r = 0.95, P < 0.0001), and protamine and disulfide bonds (r = 0.4100, P < 0.01986). Since chromatin integrity, protamine deficiency and packaging were all associated with fertility, a combination of these factors could be used as a biomarker of fertility when assessing ejaculates.

Effects of egg yolk level, penetrating cryoprotectant, and pre-freeze cooling rate, on the post-thaw quality of stallion sperm

The current study determined the effect of the egg-yolk (phospholipid source) level (egg yolk [20% EY] vs. skim-milk + egg yolk [SM + 2% EY]), cryoprotectant (glycerol [Gly] vs. glycerol + methylformamide [Gly + MF]), and pre-freeze cooling rate (-0.1 vs. -1 vs. -5 °C/min) on post-thaw stallion sperm quality. In Experiment 1, ejaculates (n = 27) from 9 stallions (3 ejaculates each) with varied sperm quality (High, Average, or Low) were frozen in EY-Gly, SMEY-Gly, EY-Gly + MF, or SMEY-Gly + MF extenders. Sperm in each group were cooled from 22° to 5°C using either -0.1 °C/min or -1 °C/min linear cooling rates prior to freezing. In Experiment 2, ejaculates (n = 24) from 12 stallions (2 ejaculates each) with High or Average sperm quality were frozen in EY-Gly, EY-Gly + MF, or in BotuCrio (BC) extenders. Sperm in each group were cooled from 22° to 5°C using either -1 or -5 °C/min linear cooling rates prior to freezing. In Experiment 1, for stallions with High or Average sperm quality, either cooling rate generally resulted in lower sperm quality for the SMEY-based extenders than for the EY-based extenders (P < 0.05). Stallions with Low sperm quality were unaffected by any experimental treatment (P > 0.05). In Experiment 2, a -5 °C/min cooling rate yielded lower sperm quality in BC than in EY-Gly or EY-Gly + MF groups (P < 0.05); however, a -1 °C/min cooling rate yielded similar sperm quality among these treatments (P > 0.05). In summary, the phospholipid level in the freezing extender and the pre-freeze cooling rate, but not the penetrating cryoprotectant, affected the post-thaw quality of stallion sperm.

Drying and temperature induced conformational changes of nucleic acids and stallion sperm chromatin in trehalose preservation formulations

Even though dried sperm is not viable, it can be used for fertilization as long as its chromatin remains intact. In this study, we investigated drying- and temperature-induced conformational changes of nucleic acids and stallion sperm chromatin. Sperm was diluted in preservation formulations with and without sugar/albumin and subjected to convective drying at elevated temperatures on glass substrates. Accumulation of reactive oxygen species was studied during storage at different temperatures, and the sperm chromatin structure assay was used to assess DNA damage. Fourier transform infrared spectroscopy was used to identify dehydration and storage induced conformational changes in isolated DNA and sperm chromatin. Furthermore, hydrogen bonding in the preservation solutions associated with storage stability were investigated. Reactive oxygen species and DNA damage in dried sperm samples were found to accumulate with increasing storage temperature and storage duration. Non-reducing disaccharides (i.e., trehalose, sucrose) and albumin counteracted oxidative stress and preserved sperm chromatin during dried storage, whereas glucose increased DNA damage during storage. When sperm was dried in the presence of trehalose and albumin, no spectral changes were detected during storage at refrigeration temperatures, whereas under accelerated aging conditions, i.e., storage at 37 °C, spectral changes were detected indicating alterations in sperm chromatin structure.

A Modified Flotation Density Gradient Centrifugation Technique Improves the Semen Quality of Stallions with a High DNA Fragmentation Index

Sperm DNA fragmentation compromises fertilization and early embryo development. Since spermatozoa lack the machinery to repair DNA damage, to improve the likelihood of establishing a healthy pregnancy, it is preferable to process ejaculates of stallions with a high sperm DNA fragmentation index (DFI) before artificial insemination or intracytoplasmic sperm injection. The aim of this study was to examine a modified flotation density gradient centrifugation (DGC) technique in which semen was diluted with a colloid solution (Opti-prepTM) to increase its density prior to layering between colloid layers of lower and higher density. The optimal Opti-prepTM solution (20-60%) for use as the bottom/cushion layer was first determined, followed by a comparison between a modified sedimentation DGC and the modified flotation DGC technique, using different Opti-prepTM solutions (20%, 25% and 30%) as the top layer. Finally, the most efficient DGC technique was selected to process ejaculates from Friesian stallions (n = 3) with high sperm DFI (>20%). The optimal Opti-prepTM solution for the cushion layer was 40%. The modified sedimentation technique resulted in two different sperm populations, whereas the modified flotation technique yielded three populations. Among the variants tested, the modified flotation DGC using 20% Opti-prepTM as the top layer yielded the best results; the average sperm recovery was 57%; the DFI decreased significantly (from 12% to 4%) and the other sperm quality parameters, including progressive and total motility, percentages of spermatozoa with normal morphology and viable spermatozoa with an intact acrosome, all increased (p < 0.05). In Friesian stallions with high sperm DFI, the modified flotation DGC markedly decreased the DFI (from 31% to 5%) and significantly improved the other semen quality parameters, although sperm recovery was low (approximately 20%). In conclusion, stallion sperm DFI and other sperm quality parameters can be markedly improved using a modified flotation DGC technique employing a 40% Opti-prepTM cushion and a 20% top layer.

The effects of metabolic substrates glucose, pyruvate, and lactate added to a skim milk-based semen extender for cooled storage of stallion sperm

Under in vitro conditions, stallion sperm might preferentially use energy substrates that primarily undergo mitochondrial metabolism. The present study sought to determine the effects of glucose, pyruvate, lactate, or their combinations on the quality of stallion sperm subjected to cooled storage at different temperatures, when using a skim milk-based semen extender. In Experiment 1, no substrate (Control), glucose (40 mM; Glu-40), pyruvate (2 mM, 19.8 mM; Pyr-2, Pyr-19), lactate (2 mM, 19.8 mM; Lac-2, Lac-19, respectively), or their combinations (G/P/L-2 or G/P/L-19, respectively) were added to a milk-based extender and their effects were determined on motion characteristics, viability/acrosomal intactness (VAI), lipid peroxidation status (VLPP), and DNA integrity (COMP_α-t) of sperm incubated for 1 h at 37 °C, or sperm stored for 24 h at either 10 or 20 °C. At any period and temperature tested, Glu-40, G/P/L-2, and G/P-L-19 resulted in similar motion characteristics (P > 0.05) but were higher than that of other treatment groups (P < 0.05). Mean VAI was highest in Glu-40 (P < 0.05). Mean VLPP was highest in G/P/L-2 and G/P/L-19 groups (P < 0.05), and mean COMP_α-t was lowest in Control, Glu-40, G/P/L-2 and G/P/L-19 groups (P < 0.05). All measures of sperm quality were higher in semen stored at 10 °C than 20 °C (P < 0.05). In Experiment 2, increasing concentrations of either pyruvate or lactate (Pyr-40, Lac-40 or Pyr-80, Lac-80) were added to the extender as energy substrates and compared to glucose (40 mM), following storage for 72 h at either 10 or 20 °C. Groups Glu-40 and Pyr-40 yielded similar sperm motion characteristics and VAI, while VLPP and COMP_α-t were reduced in these treatment groups, as compared to Pyr-80, Lac-40, and Lac-80 (P < 0.05). All measures of sperm quality were higher in semen stored at 10 °C vs 20 °C (P < 0.05). This study demonstrates that at storage temperatures of 10 or 20 °C, stallion sperm quality is optimized by the presence of glucose in a skim milk-based semen extender. The addition of substrates that readily support oxidative phosphorylation (i.e., pyruvate or lactate) did not improve the quality of stallion sperm over that of glucose alone and resulted in deleterious effects on sperm quality over time. These effects appeared to be associated with oxidative stress. Use of pyruvate (40 mM) as an alternative energy substrate to glucose generally yielded similar results to that of glucose when sperm were stored at 10 °C only.

Chemotactic selection of frozen-thawed stallion sperm improves sperm quality and heterologous binding to oocytes

The successful use of assisted reproduction techniques (ART) depends in part on the sperm physiological status. Several sperm selection procedures have been applied to improve quality of sperm population when using the ART. There has previously been development of a Sperm Selection Assay (SSA) for humans which is based on the attraction of capacitated sperm by chemotaxis towards progesterone (P), resulting in an enriched sperm population with an optimal physiological status similar to capacitated spermatozoa, with these cells having very little DNA fragmentation and optimal concentrations of reactive oxygen species (ROS). In the present study, the aim was to adapt the SSA for frozen-thawed stallion semen samples and evaluate the functional status of those sperm selected using the SSA procedure, and to determine whether this enriched sperm population has a greater capacity to bind to the zona pellucida of cattle oocytes. There were experimental conditions developed to conduct the SSA with stallion sperm. Using these conditions, the indexes of induced acrosome reaction, protein tyrosine phosphorylation, mitochondrial membrane potential, mitochondrial and cytoplasmic reactive oxygen species, and number of sperm bound to the zona pellucida of cattle were greater when the sperm population was selected using the SSA. Consistently, the DNA fragmentation and phospholipase C zeta indexes were less for the selected sperm. In conclusion, stallion sperm selected using chemotaxis utilizing the SSA provides a sperm population of greater quality, which when used may improve the outcomes with use of the ART.

Comparison of different mathematical models to assess seasonal variations in the longevity of DNA integrity of cooled-stored stallion sperm

Dynamic assessment of sperm DNA fragmentation (SDF) has shown to give fuller understanding of stallion semen quality; however, there have been limited attempts to use this parameter to investigate seasonal changes in productive functions. The aims of this study were to: (a) establish a reliable mathematical model to describe the longevity of cooled-stored sperm DNA integrity; (b) to examine the effect of seasonal variations on SDF. Ejaculates were cooled to 5°C, and SDF was analysed after 0, 6 and 24 hr of storage. The coefficient of determination (R² ) was calculated after fine-tuning linear (LIN), exponential (EXP) and second order polynomial (POL) models. R² was significantly higher (p < .001) for POL than for LIN and EXP. The rate of DNA degradation was calculated using the slopes of POL equations. After assessing the rate of change of the POL functions, significant differences between the acceleration of DNA fragmentation were found (p < .01) among seasons, being higher for winter and summer than spring and autumn. In conclusion, DNA analysis of stallion sperm fits better to a second order polynomial mathematical model, being spring the best season to collect and process cooled stallion semen in order to maintain the DNA integrity of the stallion sperm.

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

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

Effects of Different Freezing Protocols on Motility, Viability, Mitochondrial Membrane Potential, Intracellular Calcium Level, and DNA Integrity of Cryopreserved Equine Epididymal Sperm

The aim of the present study was to evaluate the effect of different freezing procedures on sperm motion, viability, the acrosome status, mitochondrial membrane potential (MMP), intracellular calcium content, and DNA integrity on epididymal stallion sperm. Therefore, the sperm of 10 healthy stallions was harvested by retrograde flushing after testectomy, diluted with a semen extender containing defined milk proteins and a freezing extender containing egg yolk and glycerol and frozen according to 4 different protocols, using a programmable freezer and a floating rack performing a slow (processes 1 and 2) or a fast cooling rate (processes 3 and 4, respectively). Post-thaw total motility and slow sperm values were lower when using process 4 compared with processes 1 and 2 (P < .05) after 1 hour of incubation. Progressive motility was lower in process 4 compared with process 1 immediately after thawing and after 1 hour of incubation (P < .05). The amount of rapid sperm was lower when using process 4 compared with process 1 immediately after thawing (P < .05). After 1 hour of incubation, the amount of rapid sperm was lower when using process 4 compared with processes 1 and 2 (P < .05). Higher values for viable sperm were seen in processes 1 and 2 compared with process 4 (P < .05) after 1 hour of incubation. Immediately after thawing, more viable sperm with high MMP (hMMP) were observed when using process 3 compared with process 2 (P < .05). After 1 hour of incubation, a significantly higher amount of viable hMMP sperm were detected when using processes 1 and 2 compared with process 4 (P < .05). Process 2 yielded a lower percentage of sperm containing low calcium (lCa) than process 3 immediately after thawing (P < .05). After 1 hour of incubation, the lowest amount of lCa sperm was observed using process 4 (P < .05). The subpopulation of viable/hMMP/lCa sperm was higher when using process 3 compared with process 2 immediately after thawing (P < .05). After 1 hour of incubation, the lowest amount of this subpopulation was detected in process 4 (P < .05). The DNA integrity was similar in all groups. In conclusion, a slow cooling rate with a controlled rate freezer resulted in best sperm quality after thawing. Using a floating rack in nitrogen vapor as an alternative to a programmable freezer, equilibration in a cooled environment is advantageous.

Effect of artificial vagina lubricants on stallion sperm quality

Commercially available vaginal lubricants, typically labeled as non-spermicidal, are used to lubricate equine artificial vaginas prior to semen collection. Improper type or amount of lubricant might affect stallion sperm quality, either after short-time exposure or following cooled storage of extended semen previously exposed to lubricant. The aim of this study was to evaluate stallion sperm quality following exposure to lubricant-containing extender for 1 h (T1h) or 24 h (T24h). Three ejaculates were collected from each of four stallions using a small volume of petrolatum to lubricate artificial vaginas, and gel-free semen was diluted to 30 × 10⁶ sperm/mL in extender containing: no lubricant (control), or 1 or 5% (v/v) HR® Lubricating Jelly (HR1 or HR5); K-Y® Jelly (KY1 or KY5); Therio-gel® (TG1 or TG5); Priority Care® Sterile Lubricating Jelly (PC1 or PC5); or Clarity® A.I. Lubricating Jelly (CL1 or CL5). Sperm were evaluated at T1h and T24h for percentages of: total and progressive sperm motility (TMOT and PMOT); curvilinear velocity (VCL; μm/s); and straightness (STR; %); viable acrosome intact sperm (VAI); sperm with abnormal DNA (COMP-α_t); viable lipid peroxidation negative sperm (VLPN); and sperm with no detectable DNA oxidative injury [8OHdG(-)]. Following short-term exposure of sperm to lubricants, KY5 reduced TMOT, PMOT, VCL, VAI, VLPN, and COMP-α_t in comparison with controls (i.e., P < 0.05). PC5 reduced TMOT, PMOT, VCL, VAI, and 8OHdG(-), and KY1 reduced TMOT, VAI, VLPN in comparison to controls (P < 0.05). Lubricant CL1, HR1 and HR5 yielded similar values to controls for all 8 endpoints, and CL5 yielded similar values to controls for all 8 endpoints (P > 0.05), except for VCL. Following long-term exposure, KY5 decreased TMOT, PMOT, VCL, VAI, VLPN, and COMP-α_t as compared to controls (i.e., P < 0.05), PC5 decreased TMOT, VCL, VAI, and 8OHdG(-)as compared to controls in PC5, and KY1 decreased TMOT, VAI, VLPN, and COMP-α_t (P < 0.05). TG5 decreased TMOT, PMOT, and VCL as compared to controls (P < 0.05). Lubricant CL5 decreased VCL (P < 0.05), and CL1, HR5, HR1, PC1, and TG1 were similar to controls for all 8 endpoints (P > 0.05). Overall, lubricant KY was the most detrimental to sperm quality, with most profound changes detected at a 5% concentration. Lubricants CL and HR were generally similar to controls and were less affected by lubricant concentration.

Comparison of the Effects of Five Semen Extenders on the Quality of Frozen-Thawed Equine Epididymal Sperm

Cryopreservation of epididymal sperm allows the saving of genetic material in case of unexpected death or emergency castration. The aim of the present study was the comparison of five different combinations of extenders commercially available for equine frozen semen processing for cryopreservation of epididymal sperm. Epididymal sperm were harvested from gonads of 10 healthy stallions after routine castration by retrograde flush technique. Then, samples were split and diluted with (1) INRA96 + INRA Freeze, (2) BotuSemen + BotuCRIO, (3) EquiPlus + Gent Freeze, (4) EquiPlus + EquiPlus Freeze, and (5) Gent + Gent Freeze. Extenders 1 and 2 showed higher values for total and progressive motility after thawing compared with extender 4 (P < .05). Extender 3 was in between 1 and 2 (P > .05), and extender 5 resulted in the lowest values (P < .05). The subpopulation of viable frozen-thawed sperm with high mitochondrial membrane potential and low intracellular calcium content was higher using extender 1 compared with extenders 3, 4, and 5 (P < .05) and higher in extender 2 compared with extenders 4 and 5 immediately after thawing (P < .05). After 1 hour of incubation, this subpopulation yielded the highest values in extender 2 (P < .05). Immediately after thawing, extender 1 yielded higher values for percentage of DFI and mean DFI than extenders 3, 4, and 5 (P < .05). Following 1 hour of incubation after thawing, sperm processed with extender 1 resulted in the highest values for percentage of DFI and mean DFI (P < .05). Using extender 2, mean DFI values were lower than those in extender 1 and higher than the extenders 3, 4, and 5 (P < .05). The study revealed that according to the examined sperm quality parameters, freezing extenders (extender 1, extender 2) using low concentrations of glycerol either combined with or without methylformamide were beneficial for cryopreservation of stallion epididymal sperm. For processing of stallion epididymal sperm, an extender containing milk proteins (extenders 1-4) for initial dilution after sperm harvesting is preferable to an extender including egg yolk (extender 5).

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.

Freezing, Vitrification, and Freeze-Drying of Equine Spermatozoa: Impact on Mitochondrial Membrane Potential, Lipid Peroxidation, and DNA Integrity

Maintaining the integrity of equine sperm subjected to preservation protocols is essential for the successful development of assisted reproduction procedures. The aim of this study was to assess the mitochondrial membrane potential, lipid peroxidation, and DNA integrity of equine sperm subjected to freezing, vitrification, and freeze-drying. Eight ejaculates obtained from four Colombian Creole horses were subjected to programmable freezing, vitrification, and freeze-drying. After thawing or rehydration, sperm motility and kinetics were assessed through a CASA system. The mitochondrial membrane potential (ΔΨM), lipid peroxidation (LPO), and DNA fragmentation index (DFI) of the spermatozoa were assessed by flow cytometry using the DiOC6 (3), C11-Bodipy 581/591, and propidium iodide (PI) fluorescent dyes. The statistical analysis was conducted via generalized linear models, mean comparisons via the Duncan test, and a principal component analysis. A higher rate of spermatozoa with a high ΔΨM was found for freeze-drying (40.26 ± 7.79%) compared with freezing (21.82 ± 5.38%) and vitrification (5.32 ± 1.17%) (P < .05). Likewise, a higher rate of nonperoxidized viable spermatozoa (Bodipy-/PI-) was found for freeze-drying (35.98 ± 7.01%) in relation to frozen (10.34 ± 2.69%) and vitrified (7.07 ± 2.00%) sperm (P < .05). The DFI of vitrified spermatozoa (0.12 ± 0.04%) was higher when compared with the frozen (0.03 ± 0.01%) and freeze-dried (0.02 ± 0.01%) samples (P < .05). The researchers conclude that vitrification generates greater sperm alterations than freeze-drying and freezing, whereas freeze-drying produces lower LPO and higher ΔΨM for equine spermatozoa.

Sperm DNA integrity in Landrace and Duroc boar semen and its relationship to litter size

The sperm chromatin structure assay is a method for assessment of sperm DNA fragmentation, a parameter reported to be negatively related to field fertility in several mammal species. This method calculates a DNA fragmentation index (DFI) whose high values indicate abnormal chromatin structure. In this study, running from March 2010 until June 2017, the aim was to assess sperm DFI in stored liquid extended semen from two different pig breeds, Norwegian Landrace (NL; n = 693) and Norwegian Duroc (ND; n = 655), and to evaluate the influence on total number of piglets born (TNB). There was a significantly higher median DFI (p < 0.0001) in ejaculates from the 478 ND boars compared to the 452 NL boars. Data from 19,496 NL litters and 3,877 ND litters of the same boars were retrieved. For either breed, sow herd (p < 0.0001), parity (p < 0.05) and DFI (p < 0.05) showed significant effects on TNB. The DFI was negatively correlated to TNB in both breeds. The boars with the 5% lowest TNB had a least square means DFI of 3.05% and 2.24% in NL and ND, respectively, compared to 1.67% and 1.23% for the boars with the 5% highest TNB (p < 0.01). The DFI and the motility of the same semen samples were negatively correlated (p < 0.0001), and the high and low TNB groups showed significant differences in motility. However, this difference could not be used for practical prediction of TNB group (92.1% vs. 89.7%; p = 0.0038 and 92.3% vs. 89.5%; p = 0.018; NL and ND, respectively). In conclusion, our results indicate that sperm DNA integrity in semen with good motility and morphology may be an additional prediction parameter for fertility in pigs.

The assessment of sperm DNA fragmentation in the saltwater crocodile (Crocodylus porosus)

Herein we report a method of assessing DNA fragmentation in the saltwater crocodile using the sperm chromatin dispersion test (SCDt) after including frozen-thawed spermatozoa in a microgel (Halomax; Halotech DNA, Madrid, Spain). Following controlled protein depletion, which included a reducing agent, sperm nuclei with fragmented DNA showed a homogeneous and larger halo of chromatin dispersion with a corresponding reduced nucleoid core compared with sperm with non-fragmented DNA. The presence of DNA damage was confirmed directly by incorporation of modified nucleotides using in situ nick translation (ISNT) and indirectly by studying the correlation of the SCDt with the results of DNA damage visualisation using a two-tailed comet assay (r=0.90; P=0.037). Results of the SCDt immediately following thawing and after 5h incubation at 37°C in order to induce a range of DNA damage revealed individual crocodile differences in both the baseline level of DNA damage and DNA longevity.

Sodium-dependent organic anion transporter (Slc10a6-/-) knockout mice show normal spermatogenesis and reproduction, but elevated serum levels for cholesterol sulfate

The sodium-dependent organic anion transporter SOAT (gene name SLC10A6 in man and Slc10a6 in mice) is a plasma membrane transporter for sulfated steroids, which is highly expressed in germ cells of the testis. SOAT can transport biologically inactive sulfated steroids into specific target cells, where they can be reactivated by the steroid sulfatase (STS) to biologically active, unconjugated steroids known to regulate spermatogenesis. Significantly reduced SOAT mRNA expression was previously found in different forms of impaired spermatogenesis in man. It was supposed that SOAT plays a role for the local supply of steroids in the testis and consequently for spermatogenesis and fertility. Thus, an Slc10a6^-/- Soat knockout mouse model was established by recombination-based target deletion of the Slc10a6 gene to elucidate the role of Soat in reproduction. However, the Slc10a6^-/- knockout mice were fertile, produced normal litter sizes, and had normal spermatogenesis and sperm vitality. This phenotype suggests that the loss of Soat can be compensated in the knockout mice or that Soat function is not essential for reproduction. In addition to reproductive phenotyping, a comprehensive targeted steroid analysis including a set of 9 un-conjugated and 12 sulfo-conjugated steroids was performed in serum of Slc10a6^-/- knockout and Slc10a6^+/+ wildtype mice. Only cholesterol sulfate, corticosterone, and testosterone (only in the males) could be detected in considerable amounts. Interestingly, male Slc10a6^-/- knockout mice showed significantly higher serum levels for cholesterol sulfate compared to their wildtype controls. As cholesterol sulfate has a broader impact apart from the testis, further analysis of this phenotype will include other organs such as skin and lung, which also show high Soat expression in the mouse.

Determinants of gestation length in Thoroughbred mares on German stud farms

The aim of the present study was to analyze the effects of stallion and mare, their ages, and maternal lineage on the gestation length (GL) in Thoroughbreds. In addition, additive genetic effects of the dam, stallion and fetus were analyzed. Data were taken from 1993 through 2009, and included 16,226 pregnancies from 5959 Th oroughbred mares mated with 290 different stallions. All analyses were performed using linear mixed models. The GL ranged from 306 to 390 days, with a mean length of 347.0 ± 14.4 days. Mating of mares with stallions aged 17 years and older resulted in a significantly longer GL compared to younger stallions. Furthermore, the GL significantly increased with the increasing age of the mares, and the GL was longer with male foals. The month and year of breeding, as well as the mare´s breeding history (parity and reproductive status) also affected GL. The mare and stallion themselves explained 18% and 4% of the variance in GL. Coefficients of inbreeding of mares and foals had no significant effect on GL. The heritability for the GL was 0.17 for the dam and 0.006 for the fetus, whereas an additive genetic paternal effect was not estimable. The relative proportions among the additive genetic and permanent environmental contributions of the dam were 76.5% and 23.5%. A maternal lineage effect was not obvious.

Pulse Doppler ultrasound as a tool for the diagnosis of chronic testicular dysfunction in stallions

Testicular function is particularly susceptible to vascular insult, resulting in a negative impact on sperm production and quality of the ejaculate. A prompt diagnosis of testicular dysfunction enables implementation of appropriate treatment, hence improving fertility forecasts for stallions. The present research aims to: (1) assess if Doppler ultrasonography is a good tool to diagnose stallions with testicular dysfunction; (2) to study the relationship between Doppler parameters of the testicular artery and those of sperm quality assessed by flow cytometry and (3) to establish cut off values to differentiate fertile stallions from those with pathologies causing testicular dysfunction. A total of 10 stallions (n: 7 healthy stallions and n: 3 sub-fertile stallions) were used in this study. Two ejaculates per stallion were collected and preserved at 5°C in a commercial extender. The semen was evaluated at T0, T24 and T48h by flow cytometry. Integrity and viability of sperm (YoPro®-1/EthD-1), mitochondrial activity (MitoTracker® Deep Red FM) and the DNA fragmentation index (Sperm Chromatin Structure Assay) were assessed. Doppler parameters were measured at three different locations on the testicular artery (Supratesticular artery (SA); Capsular artery (CA) and Intratesticular artery (IA)). The Doppler parameters calculated were: Resistive Index (RI), Pulsatility Index (PI), Peak Systolic Velocity (PSV), End Diastolic Velocity (EDV), Time Average Maximum Velocity (TAMV), Total Arterial Blood Flow (TABF) and TABF rate. The capsular artery was the most reliable location to carry out spectral Doppler assessment, since blood flow parameters of this artery were most closely correlated with sperm quality parameters. Significant differences in all the Doppler parameters studied were observed between fertile and subfertile stallions (p ≤ 0.05). The principal components analysis assay determined that fertile stallions are characterized by high EDV, TAMV, TABF and TABF rate values (high vascular perfusion). In contrast, subfertile stallions tend to present high values of PI and RI (high vascular resistance). The ROC curves revealed that the best Doppler parameters to predict sperm quality in stallions were: Doppler velocities (PSV, EDV and TAMV), the diameter of the capsular artery and TABF parameters (tissue perfusion parameters). Cut off values were established using a Youden´s Index to identify fertile stallions from stallions with testicular dysfunction. Spectral Doppler ultrasound is a good predictive tool for sperm quality since correlations were determined among Doppler parameters and markers of sperm quality. Doppler ultrasonography could be a valuable diagnostic tool for use by clinical practitioners for the diagnosis of stallions with testicular dysfunction and could be a viable alternative to invasive procedures traditionally used for diagnosis of sub-fertility disorders.

Modern Techniques for Semen Evaluation

Stallion semen evaluation is an important part of the breeding soundness evaluation. The results of the semen evaluation cannot be interpreted without a thorough knowledge of the mare and management effects that may have played a role or may affect the potential fertility of the stallion evaluated. There are considerations and limitations that the clinician should understand about each test. Any sperm quality test must be interpreted with a clear understanding of how it relates to fertility.

Dynamics of sperm DNA fragmentation in raw boar semen and fertility

The aims were to evaluate sperm DNA fragmentation (SDF) in boars through the dispersion of their chromatin in raw semen samples, quantifying the extent of SDF, and to assess dynamic aspects of sperm DNA damage after incubation to obtain the rate of sperm DNA fragmentation (rSDF) under thermal conditions similar to the uterus (37°C) over a period of up to 24 hr and to correlate the reproductive outcome of the sows with the SDF of the boars at ejaculation. The study was performed on a pig-breeding farm in southern Uruguay. Sixty-one ejaculates from five of the most frequently used hybrid boars were evaluated. Semen was collected weekly from each of the boars, using the gloved-hand technique and discarding the jelly-like fraction of the ejaculate. Fresh semen was kept in a water bath at 37°C and protected from light, and was thereafter processed with Sperm-Sus-Halomax(®) to evaluate SDF. The smears for time 0 (T0) were made on farm, and thereafter smears were made at the laboratory at 4 hr of obtaining the semen (T4), then every 2 hr (T6, T8, T10, T12) and a final fixation at 24 hr (T24). Differences in SDF were observed among exposure times for all boars (p < .05), but not between T10 and T12 (p = .7751) nor T4 and T24 (p = .9113). In none of the T24 samples, sperm heads could be seen with chromatin dispersion halos. Furthermore, there were differences among boars when comparing sperm rSDF (p < .05). Farrowing rate was not affected by SDF at T0 (r = .38, p = .75), nor was litter size (r = .16, p = .70). With the present experimental conditions, we have not been able to show a relationship between sperm DNA fragmentation at ejaculation and reproductive performance. However, this could be a result of the low number of ejaculates and boars used.

New flow cytometry approaches in equine andrology

Flow cytometry is currently recognized as a robust tool for the evaluation of sperm quality and function. However, within equine reproduction, this technique has not reached the sophistication of other areas of biology and medicine. In recent years, more sophisticated flow cytometers have been introduced in andrology laboratories, and the number of tests that can be potentially used in the evaluation of sperm physiology has increased accordingly. In this review, recent advances in the evaluation of stallion spermatozoa will be discussed. These new techniques in flow cytometry are able to simultaneously measure damage to different sperm regions and/or changes in functionality.

Fourier transform infrared spectroscopic analysis of sperm chromatin structure and DNA stability

Sperm chromatin structure and condensation determine accessibility for damage, and hence success of fertilization and development. The aim of this study was to reveal characteristic spectral features coinciding with abnormal sperm chromatin packing (i.e., DNA-protein interactions) and decreased fertility, using Fourier transform infrared spectroscopy. Chromatin structure in spermatozoa obtained from different stallions was investigated. Furthermore, spermatozoa were exposed to oxidative stress, or treated with thiol-oxidizing and disulfide-reducing agents, to alter chromatin structure and packing. Spectroscopic studies were corroborated with flow cytometric analyses using the DNA-intercalating fluorescent dye acridine orange. Decreased fertility of individuals correlated with increased abnormal sperm morphology and decreased stability toward induced DNA damage. Treatment with the disulfide reducing agent dithiothreitol resulted in increased sperm chromatin decondensation and DNA accessibility, similar as found for less mature epididymal spermatozoa. In situ infrared spectroscopic analysis revealed that characteristic bands arising from the DNA backbone (ν1230, ν1086, ν1051 cm(-1) ) changed in response to induced oxidative damage, water removal, and decondensation. This coincided with changes in the amide-I region (intensity at ν1620 vs. ν1640 cm(-1) ) denoting concomitant changes in protein secondary structure. Reduction in protein disulfide bonds resulted in a decreased value of the asymmetric to symmetric phosphate band intensity (ν1230/ν1086 cm(-1) ), suggesting that this band ratio is sensitive for the degree of chromatin condensation. Moreover, when analyzing spermatozoa from different individuals, it was found that the asymmetric/symmetric phosphate band ratio negatively correlated with the percentage of morphologically abnormal spermatozoa.

Sperm DNA quality evaluated by comet assay and sperm chromatin structure assay in stallions after unilateral orchiectomy

Unilateral orchiectomy (UO) may interfere with thermoregulation of the remaining testis caused by inflammation surrounding the incision site, thus altering normal spermatogenesis and consequently sperm quality. Two measures of sperm DNA quality (neutral comet assay and the sperm chromatin structure assay [SCSA]) were compared before UO (0 days) and at 14, 30, and 60 days after UO to determine whether sperm DNA changed after a mild testis stress (i.e., UO). The percent DNA in the comet tail was higher at 14 and 60 days compared to 0 days (P < 0.05) after UO. All other comet tail measures (i.e., length, moment, migration) were higher at all time periods after UO compared to 0 days (P < 0.05). Two SCSA measures (mean-αt, mode-αt) increased at 14 days after UO (P < 0.05), whereas two measures (SD-αt and COMP-αt) did not change. This study identified a decrease in sperm DNA quality using both the neutral comet assay and the SCSA, which was not identified using traditional measures of sperm quality.