Optimization of ram semen cryopreservation using a chemically defined soybean lecithin-based extender

The effects of supplementation of vitamin D to the egg-yolk extender on cryopreservation of ram semen

OBJECTIVES

This study aimed to examine the effects of supplementation of vitamin D to the egg-yolk extender on characteristics of frozen-thawed ram semen.

METHODS

Semen samples obtained from adult rams were pooled and divided into five equal volumes. It was reconstituted with extenders containing different concentrations of vitamin D: 0 (control), 12.5 (VITD 12.5), 25 (VITD 25), 50 (VITD 50), and 100 ng/mL (VITD 100), and then they were frozen. Sperm motility parameters, plasma membrane functional integrity, acrosomal integrity, DNA fragmentation, and mitochondrial membrane potential of the groups were evaluated after sperm thawing.

RESULTS

Total motility and progressive motility were higher in VITD 50 than in all other groups (p < 0.05). Higher sperm straightness, linearity, and wooble were higher in VITD 50 than in the control group (p < 0.05). A similar pattern of VITD 50 was observed for plasma membrane integrity and mitochondrial membrane potential (p > 0.05).

CONCLUSIONS

In the study, it was observed that adding vitamin D to the extender had a beneficial effect on ram spermatological parameters. In addition, it was concluded that the use of the 50 ng/mL vitamin D in the extender provided more effective protection than the other doses.

Coenzyme Q10 preserves buck's sperm quality during cryopreservation process in plant-based extender

Cryopreservation of small ruminant's semen is an effective strategy for distributing spermatozoa for reproductive programs, but this process decreases the fertility potential of post-thawed spermatozoa. The aim of this research was to assess the effect of different concentrations of CoQ10 in soybean lecithin (SL)-based extender on buck semen quality during cryopreservation process. Semen samples were collected from five bucks, twice a week, then diluted in the SL-based extender containing different concentrations of CoQ10 as follows: extender containing 0 µM (control, Q0), 0.1 µM (Q0.1), 1 µM (Q1), 10 µM (Q10) and 100 µM (Q100) CoQ10. Motion characteristics, membrane functionality, abnormal morphology, mitochondrial activity, acrosome integrity, viability, apoptotic-like changes, lipid peroxidation, DNA fragmentation and ROS concentration were evaluated after freeze-thawing process. The Q10 resulted in greater (P≤0.05) total motility, progressive motility, average path velocity, membrane integrity, mitochondrial activity, acrosome integrity and viability compared to the other groups. Furthermore, supplementation of freezing extender with 10 µM of CoQ10 presented lower (P≤0.05) apoptotic-like changes, lipid peroxidation, DNA fragmentation and ROS concentration compared to the other groups. Regarding to the protective effect of CoQ10 supplement during cryopreservation process, it could be explored as a potent antioxidant for cryopreservation of buck semen as it preserved the post-thawed buck sperm quality.

Effects of different extenders, storage temperatures, and antioxidant supplementation on chilled semen quality: a review

The successful preservation of ram semen is essential to promote genetic variability, ensure semen transportation, and inseminate multiple ewes. Currently, either animal or plant-based lipoprotein-based extenders are used for semen preservation. Animal product-based extenders include milk and egg yolk, while soybean lecithin is a plant-based extender. Although extenders containing products of animal origin better preserve the quality of chilled semen, the in vivo efficacy after 24 h of storage is still of great concern. Storage temperature is another important and effective factor in preserving sperm quality, whereby different storage temperatures are adopted to enhance the storage life of sperm. Low temperatures (4-5 °C) better preserve sperm quality for a longer duration than high temperatures (15, 20, and 25 °C). Moreover, antioxidant supplementation has a positive impact on sperm quality during liquid storage. The current review summarizes the outcomes of various extenders, different storage temperatures, and antioxidant supplementation on the liquid storage of ram sperm.

A soy lecithin nanoparticles-based extender effectively cryopreserves Holstein bull sperm

Plant-based semen extenders, typically derived from soybean lecithin, are easier to modulate more and consistent in their composition than animal-based extenders. As large lecithin particles can, however, reduce effectiveness and solubility in bull semen extenders, sonication was used to create nano-lecithin (NL) particles of soybean lecithin. The objective was to determine the effects of lecithin type and concentration on the quality of frozen-thawed bovine sperm. We hypothesized that reducing the size of lecithin improves its interactions with the sperm and enhances the parameters that favor its motility, viability and fertility. Semen was collected from six mature Holstein bulls and ejaculates meeting minimum standards were pooled. Eight Tris-based extenders that contained 1, 2, 3, or 4 % of either conventional lecithin (L1-L4) or NL (NL1-NL4), plus two control extenders (one animal-based extender containing 20 % egg yolk [EY] and a commercial lecithin-based extender [BioXcell®]) were compared. Among soybean lecithin-based extenders, NL3 had the highest total and progressive sperm motility, and average path, straight-line and curvilinear sperm velocity, and was comparable to EY. Additionally, sperm mitochondrial activity was the highest in NL3, whereas sperm viability was highest in EY, NL3, and L4. Following in vitro fertilization of in vitro-matured bovine oocyes, NL3 had cleavage and hatching rates comparable to BioXcell®, but a lower blastocyst rate than EY. Overall, NL3 performed better than the other extenders for most end points, with efficiency comparable to EY. We, therefore, concluded that reducing lecithin particle size to a nano level improves sperm cryopreservation with optimal performance with 3 % NL.

Association between different soy lecithin-based extenders and freezing rates in ram semen cryopreservation

The aim of the study was to evaluate the effect of the association between glycine-milk (GM) based extenders made with different concentrations of soy lecithin (SL) and freezing rates (FR) on semen quality after thawing. Pooled semen from rams (n = 12) were diluted in GM extenders with 20% egg yolk (EY-20%) or with different concentrations of SL: 0.5% (SL-0.5%), 1.0% (SL-1.0%), and 2.0% (SL-2.0%). The diluted semen (150 ×10⁶ spermatozoa/0.25 mL) was frozen at three FR of - 10, - 20, and - 60 °C/min, and subsequently thawed and analyzed. Results revealed that EY-20% and SL-2.0% had better kinetic parameters, and showed higher proportions of viable, non-apoptotic, plasma-membrane-intact spermatozoa (A^-/PI^-) and non-capacitated spermatozoa (F), and had lower acrosome-reacted spermatozoa (AR) in the EY-20% and satisfactory values for SL-2.0% compared to SL-0.5% and SL-1.0% (P < 0.05). The FR at - 20 and - 60 °C/min maintained higher A^-/PI^- and viable spermatozoa compared to - 10 °C/min. The combination EY-20% and - 60 °C/min showed the highest A^-/PI^- and F (P < 0.05) and the lowest AR, and it did not differ from the combinations EY-20% at - 20 °C/min and SL-2.0% at - 20 °C/min (P > 0.05). In conclusion, the combination EY-20% and - 60 °C/min, showed the best cryoprotective effects on ram spermatozoa. Changes in spermatozoa after thawing were related to the use of the type of extender, the amounts of the same compound in the extender, and the freezing rates to which they were subjected.

Fertility results after exocervical insemination using goat semen cryopreserved with extenders based on egg yolk, skim milk, or soybean lecithin

To evaluate the effects of four extenders on the post-thaw quality and fertility of goat semen, six Yunshang Black bucks' semen was collected, pooled, diluted with Andromed® (Andr®), Optidyl® (Opt®), P3644 Sigma l-phosphatidylcholine (l-α SL), and skim milk-based (Milk) extenders, and then cryopreserved. The sperm motilities, abnormalities, membrane and acrosome integrity, mitochondrial activity, apoptosis, and reactive oxygen species (ROS) production were evaluated after thawing. After exocervical insemination with the thawed semen, the pregnancy, lambing, and twinning rates were recorded and compared. The results showed that sperm motilities, membrane integrity, acrosome integrity, mitochondrial activity, and viable spermatozoa were significantly higher in the Andr® and Opt® groups than those in the l-α SL and Milk groups (p < .05). Furthermore, there was no difference between Andr® and Opt® (p > .05). The sperm abnormality was lower in semen frozen with the Andr® or Opt® extenders, as compared to the l-α SL or Milk extender (p < .05). Regarding, the viable cells with low ROS production, the optimal results were obtained in the semen frozen with Andr® and Opt® extenders. Following exocervical insemination, the pregnancy and lambing rates in the Milk group were significantly lower than those in the other groups (p < .05). No difference was found in the pregnancy and lambing rates between Andr®, Opt®, and l-α SL (p > .05). Furthermore, the twinning rates were similar between these four groups (p > .05). In conclusion, egg yolk or skim milk can be substituted by soybean lecithin during cryopreservation of goat semen.

Melatonin improves post-thaw sperm quality after mild testicular heat stress in rams

The objective was to determine effects of slow-release melatonin on post-thaw sperm quality in rams exposed to mild testicular heat stress (HS; scrotal neck insulation). Twelve yearling Dorset rams were randomly and equally allocated to receive either 36 mg melatonin in 1 ml corn oil or 1 ml corn oil injected subcutaneously (SQ); 15 day later, all rams had HS for 96 h (start of HS = start of Week 0). Semen was collected before HS and once weekly from Weeks 1 to 7, extended in Steridyl CSS One Step, held at 5°C for ~3 h, loaded into 0.5 ml straws, held 5 cm above liquid nitrogen for 10 min and then plunged. Computer assisted semen analysis (CASA) was conducted on frozen-thawed sperm. There were group and week effects for total and progressive motility (p < .001), plus group and week effects and group*week interactions (p < .001) for post-thaw total abnormalities, acrosome integrity, post-thaw sperm DNA fragmentation index (DFI) and high mitochondrial membrane potential (HMMP). Post-thaw sperm total and progressive motility, acrosome integrity and HMMP were higher (p < .05) in melatonin versus control groups from Weeks 1 to 7, and the melatonin group reached baseline level (pre-heat stress) at Week 7 (75.79 ± 0.96, 65.48 ± 1.51, 75.00 ± 0.89 and 67.00 ± 1.06, respectively; mean ± SEM). Conversely, post-thaw sperm total abnormalities and DFI were lower (p < .05) in melatonin versus control, and both reached baseline at Week 7 in the melatonin group (26.00 ± 0.57 and 5.66 ± 0.17, respectively). Coiled tails, distal midpiece reflexes, distal cytoplasmic droplets, ruffled acrosomes, bowed midpieces, pyriform heads and knobbed acrosomes were the most common abnormalities in both groups, with lower percentages in melatonin-treated rams. Results supported our hypothesis that HS reduces post-thaw sperm quality, and that melatonin lessens those reductions, manifested by significantly better total and progressive motility, acrosome integrity and HMMP, and fewer sperm total abnormalities and DFI.

Optimized addition of nitric oxide compounds in semen extender improves post-thaw seminal attributes of Murrah buffaloes

Semen dilution and cryopreservation alter the homogeneity of seminal plasma, resulting in a non-physiological redox milieu and consequently poor sperm functionality. Considering the concentration-specific bimodal action of nitric oxide (NO) in the regulation of sperm functions, cryopreservation media supplemented with optimized concentrations can improve the semen attributes. The present study aimed to evaluate the effect of adding an optimized concentration of sodium nitroprusside (SNP) and N-nitro-L-arginine methyl ester (L-NAME) in an extender on in vitro semen quality. An aliquot of semen samples (n = 32) from Murrah buffalo bulls (n = 8) was divided into control (C) and treatment (T-I: SNP in extender at 1 µmol/L; T-II: L-NAME in extender at 10 µmol/L). Fresh semen quality parameters showed no significant difference at 0 h except for the structural integrity in the T-II group. Post-thaw semen quality parameters and sperm kinematics using computer-aided sperm analysis (CASA) revealed significantly higher (p < 0.05) cryoresistance in the treatment groups. Viability, acrosome integrity, and membrane integrity were significantly higher (p < 0.05) in both treatment groups; however, the results were pervasive in T-II. Lower abnormal spermatozoa were observed in both T-I and T-II. SNP supplementation led to a significant rise (p < 0.05) in NO, whereas L-NAME reduced the NO concentration in post-thawed samples, which was directly correlated with different sperm functionality and associated biomarkers viz. total antioxidant capacity (TAC) and thiobarbituric acid reactive substance (TBARS). It was concluded that the cryopreservation media supplemented with SNP and L-NAME at 1 µmol/L and 10 µmol/L, respectively, lower the cryo-damage and improve post-thaw seminal attributes.

Cryopreservation of Semen in Domestic Animals: A Review of Current Challenges, Applications, and Prospective Strategies

Cryopreservation is a way to preserve germplasm with applications in agriculture, biotechnology, and conservation of endangered animals. Cryopreservation has been available for over a century, yet, using current methods, only around 50% of spermatozoa retain their viability after cryopreservation. This loss is associated with damage to different sperm components including the plasma membrane, nucleus, mitochondria, proteins, mRNAs, and microRNAs. To mitigate this damage, conventional strategies use chemical additives that include classical cryoprotectants such as glycerol, as well as antioxidants, fatty acids, sugars, amino acids, and membrane stabilizers. However, clearly current protocols do not prevent all damage. This may be due to the imperfect function of antioxidants and the probable conversion of media components to more toxic forms during cryopreservation.

Extend the Survival of Human Sperm In Vitro in Non-Freezing Conditions: Damage Mechanisms, Preservation Technologies, and Clinical Applications

Preservation of human spermatozoa in vitro at normothermia or hypothermia maintaining their functions and fertility for several days plays a significant role in reproductive biology and medicine. However, it is well known that human spermatozoa left in vitro deteriorate over time irreversibly as the consequence of various stresses such as the change of osmolarity, energy deficiency, and oxidative damage, leading to substantial limitations including the need for semen examinations, fertility preservation, and assisted reproductive technology. These problems may be addressed with the aid of non-freezing storage techniques. The main and most effective preservation strategies are the partial or total replacement of seminal plasma with culture medium, named as extenders, and temperature-induced metabolic restriction. Semen extenders consist of buffers, osmolytes, and antioxidants, etc. to protect spermatozoa against the above-mentioned adverse factors. Extended preservation of human spermatozoa in vitro has a negative effect on sperm parameters, whereas its effect on ART outcomes remains inconsistent. The storage duration, temperature, and pre-treatment of semen should be determined according to the aims of preservation. Advanced techniques such as nanotechnology and omics have been introduced and show great potential in the lifespan extension of human sperm. It is certain that more patients will benefit from it in the near future. This review provided an overview of the current knowledge and prospects of prolonged non-freezing storage of human sperm in vitro.

Protective effect of rosiglitazone on microscopic and oxidative stress parameters of ram sperm after freeze-thawing

The purpose of this study was to investigate the effects of rosiglitazone on ram semen after cryopreservation on the quality of thawed sperm. Sperm motility, membrane functionality, viability, total abnormality, acrosome membrane integrity, mitochondrial activity, reactive oxygen species production, ATP content and apoptotic features were assessed after thawing. Rosiglitazone at concentration of 60 µM resulted in the highest (P < 0.05) total motility, progressive motility and straight-line velocity. The percentages of average path velocity and curvilinear velocity were greater in the 60 µM group. Different concentrations of rosiglitazone did not have significant effects on amplitude of the lateral head displacement, linearity and straightness. The highest amounts of membrane functionality and mitochondrial activity after freeze-thawing were observed in groups containing 60 µM. By increasing the rosiglitazone level to 80 µM, no positive effect was observed in most of the evaluated parameters. The lowest ROS concentration was recorded in 60 µM rosiglitazone group (P < 0.05). The group containing 60 µM rosiglitazone also produced the lowest significant percentage of apoptosis-like changes and dead sperm. A greater (P < 0.05) percentage of acrosome integrity in frozen-thawed spermatozoa was observed in the 60 µM rosiglitazone group. There was no significant difference between 40 and 60 µM rosiglitazone in intact acrosome of ram thawed semen. The result showed that supplementation in ram semen extender with rosiglitazone had a positive role in the regulation of ram sperm motility and had strong protective effect on the sperm membrane and acrosome integrity.

The Cryopreserved Sperm Traits of Various Ram Breeds: Towards Biodiversity Conservation

The aim of our research was to compare three Slovak sheep breeds in the quality parameters of cryopreserved sperm. The ejaculates of Slovak Dairy (SD), Native Wallachian (NW), and Improved Wallachian (IW) sheep rams (n = 12) were collected by electro-ejaculation. Heterospermic samples were created from suitable ejaculates, separately for each breed (at least 90% of total and 80% of progressive motility). Samples were equilibrated in a Triladyl® diluent and frozen by automated freezing. Sperm samples were subjected to the motility, morphology, (CASA), viability and apoptosis (DRAQ7/Yo-Pro-1), fertilizing capability (penetration/fertilization test (P/F) in vitro) and acrosomal status (transmission electron microscopy) assays before freezing and after thawing. It was found that there were no significant differences (p < 0.05) between the evaluated breeds in motility, viability, apoptosis, morphological properties, and fertilizing ability of cryopreserved sperm. Significant differences occurred in acrosomal status. Our results demonstrate that the use of the selected cryopreservation protocol is suitable for at least three different sheep breeds, which can greatly benefit the biodiversity protection and simplifies the creation of an animal genetic resources gene bank.

Cryopreservation Techniques for Ram Sperm

Germplasm storage and transportation in artificial insemination (AI) and other advanced technologies are facilitated by cryopreservation. In reproduction, the cryopreservation of sperm allows it to be transported across vast distances and used even after the sire's death. However, the technique of cryopreservation might damage sperm and limit their activity. Several cryobiological investigations have reported that the integrity of the sperm membrane is frequently involved in the physical and biological elements that affect sperm survival at low temperatures during the cryopreservation process. However, successful cryopreservation of ram sperm is still a work in progress because a considerable percentage of sperm do not survive the freezing and thawing process. Sperms are destroyed during cryopreservation of semen due to varying concentrations of cryoprotective chemicals and if semen is not cooled at optimal cooling rates. Hence, it is crucial to know the optimum cooling rates with freezing and thawing protocols for maximum recovery of viable and functional sperm cells for a successful cryo-freezing of ram spermatozoa. Therefore, the current study compiled and compared the research on the impact of different cryopreservation procedures, cooling rates, equilibration time, and thawing protocols on post-thaw ram semen quality.

Novelties in Ovine Assisted Reproductive Technologies – A Review

Artificial insemination (AI) as a part of assisted reproductive technologies represents the oldest and most widespread method used to accelerate genetic progress in all domestic animals. After its first implementation in ovine reproduction and almost 80 years afterward, AI is continuously used for improving the genetic merit, utilizing either fresh or short-time chilled semen. Nevertheless, regardless of the semen used for insemination, the conception rate (CR) is still lower in comparison to natural service. At least two factors are commonly thought to limit the success of the AI and reduce the CR: (1) failure of placing the semen directly into the uterus due to the specific anatomic structure of the ewe’s cervix; (2) lower viability of ram spermatozoa during cryopreservation (<30% progressively motile spermatozoa after thawing). This review elaborates on recent studies that aimed to achieve acceptable CR through the implementation of cervical or intrauterine insemination: deep intracervical, intrauterine trans-cervical, and intracornual. Several hormonal treatments (oxytocin, estrogen, or prostaglandin) were evaluated on inducing cervical dilation that facilitates insemination. A comprehensive analysis was given to the effects of several antioxidants (GSSG, GSH, and cysteine) supplemented in ram semen-freezing media. Sex-sorted ram semen fertility rate results were presented from our studies.

Enhancement of sperm quality and fertility-related parameters in Hubbard grandparent rooster fed diets supplemented with soybean lecithin and vitamin E

The purpose of this study was to investigate the effect of dietary supplementation of different levels of soybean lecithin and vitamin E on semen quality parameters and some reproductive hormones in Hubbard grandparent roosters. The experiment was conducted in a 3 × 2 factorial arrangement with 3 levels of soybean lecithin (0, 1, and 2%) and 2 levels of vitamin E (0 and 300 mg/kg). Semen samples were collected on d 0, 20, 40 and 60 of the experiment and analyzed. Adding 1% soybean lecithin and vitamin E into the diet increased semen volume and sperm concentration, membrane integrity and viability (P < 0.05). Supplementing diets with 1 or 2% lecithin in addition to vitamin E significantly improved total motility and progressive motility (P < 0.05). Vitamin E significantly increased the amplitude of lateral head displacement (ALH) of sperm (P < 0.05). Although there was no effect on LH and FSH when diets were supplemented with vitamin E and 1 or 2% lecithin, testosterone concentration was increased (P < 0.05). Malondialdehyde (MDA) concentration was significantly lower in all 3 treatments containing vitamin E (P < 0.05). It can be concluded that supplementation of rooster diets with vitamin E and 1% lecithin can improve fertility related parameters in Hubbard grandparent roosters.

Cryopreservation of ram semen: Manual versus programmable freezing and different lengths of equilibration

The aim of our study was to examine effects of the length of semen equilibration as well as two freezing techniques on ram sperm post-thaw quality. The ejaculates of Wallachian sheep rams (n = 12) were collected by an electro-ejaculation, equilibrated in a Triladyl® (0, 2, 4, 6, and 8 h) containing glycerol and egg yolk and frozen by programmable freezing (PF) or manual freezing (MF). After thawing, sperm samples were subjected to the motility (computer-assisted sperm analysis [CASA]), viability (SYBR-14/PI), and fertilizing ability (FA) (in vitro penetration/fertilization test on bovine oocytes) assays. It was found that the equilibration of 6 h (E-6) ensured higher post-thaw sperm motility and progressive movement compared with other lengths tested, irrespective of a freezing technique. The E-6 sperm viability did not differ between PF and MF but was lower (P < 0.05) than control. Sperm FA (E-6) was similar in PF (60.44%) and MF (62%) but slightly lower than in fresh (72.8%). Our data demonstrate that the use of MF was comparable with PF, which can be applied in the field conditions without need in a piece of cost-expensive equipment, which can greatly benefit the gene bank of animal genetic resources.

Effect of Milk Type Subjected to Different Heat Treatments on Cryo-Survivability and In Vivo Fertility of Buffalo (Bubalus bubalis) Spermatozoa in a Milk-Based Extender

Oxidative stress is a major contributory factor to cellular damage during semen cryopreservation and results in a decreased fertilizing capacity of cryopreserved bull sperm. The inclusion of exogenous antioxidants sometimes exerts deleterious effects on sperm quality. Thus, enhancing the endogenous production of antioxidants is a requirement. This study aimed to investigate the effect of milk type heated at different temperatures on the antioxidant potential of extenders, and the subsequent post-thaw quality parameters and in vivo fertility of buffalo bull semen. Cow (C) and buffalo whole milk (B) were used separately for semen extender preparation, heated at five different temperatures (T₁ = 90°C, T₂ = 100°C, T₃ = 110°C, T₄ = 120°C, T₅ = 130°C) for 10 minutes. Reactive sulfhydryl groups were measured in each subgroup by Ellman's reagents as CT₁ = 143.2 μM, CT₂ = 147.4 μM, CT₃ = 151.5 μM, CT₄ = 157.2 μM, CT₅ = 161.8 μM, BT₁ = 168.3 μM, BT₂ = 172.5 μM, BT₃ = 176.7 μM, BT₄ = 196.3 μM, and BT₅ = 205.7 μM. All semen samples were cryopreserved in milk-based extenders by using standard procedures. Post-thaw quality parameters including total and progressive motility, mitochondrial membrane potential, plasma membrane integrity, and acrosome integrity were found to be higher (p < 0.05) in the group (BT₃) containing buffalo milk heated at 110°C, whereas in the same group, lipid peroxidation was found to be lower (p < 0.05) as compared with other treatment groups and control group. In vivo fertility of cryopreserved buffalo sperm was compared among BT₃, CT₁ (conventionally used milk extender), and a Tris egg yolk extender group. The fertility rates [47% (54/114), 30% (33/108), and 36% (37/103)] were higher (p < 0.05) in BT₃ as compared with other groups. This study suggests that buffalo milk heated at 110°C has high antioxidant potential and improves post-thaw quality and in vivo fertility of cryopreserved buffalo bull semen.

Combined Effect of Flaxseed Oil and Vitamin E Supplementation During Bull Semen Cryopreservation on Sperm Characteristics

The present study was performed to investigate the effects of supplementing flaxseed oil (FO) or vitamin E (VE) or their combination to an extender for Simmental bull semen cryopreservation. In experiment 1, different concentrations of FO (0, 10, 100, and 1000 ng/mL) and VE (0.05, 0.1, and 0.2 mg/mL) were added to the extenders. In experiment 2, FO, VE, and FO + VE were added and a control group was included. Sperm viability, motility, motion parameters, acrosome integrity and membrane integrity, endogenous antioxidant indices, reactive oxygen species, and malondialdehyde levels were evaluated after semen thawing. A higher percentage of viability, motion parameters, endogenous antioxidant indices, and membrane integrity was observed after supplementation with 10 ng/mL FO or 0.1 mg/mL VE compared with the control group (p < 0.05). Also, combined supplementation of 10 ng/mL FO +0.1 mg/mL VE further improved the quality of frozen-thawed sperm by regulating viability, motion parameters, membrane integrity, and endogenous antioxidant indices compared with the FO or VE alone (p < 0.05). These results indicated that FO (10 ng/mL) + VE (0.1 mg/mL) could further improve the protective effects on bull sperm post-thaw.

Antioxidant and Antiapoptotic Effects of a Turraea fischeri Leaf Extract on Cryopreserved Goat Sperm

This study evaluated the efficacy of Turraea fischeri leaf extract for maintaining the viability of cryopreserved goat sperm. Ejaculated semen was collected from 5 mature Baladi bucks (50-60 kg, 2-4 years of age) and those samples with mass motility ≥ 70% and sperm concentration ≥ 2.5 × 109/mL were selected, pooled, and divided into 4 aliquots. Each aliquot was diluted in Tris-citric-soybean lecithin extender containing a different concentration of T. fischeri leaf extract (0, 125, 250, or 375 µg/mL). Treated semen samples were cooled to 5 °C, transferred to 0.25-mL French straws, and stored in liquid nitrogen (LN2) at -196 °C. After thawing, membrane integrity was examined by transmission electron microscopy, apoptotic activity by Annexin/propidium iodide staining and flow cytometry, and both enzyme activities and antioxidant capacity by spectroscopic assays. The leaf extract at 375 µg/mL significantly improved semen quality as indicated by enhanced total antioxidant capacity, reduced H2O2 concentration, a greater proportion of structurally intact motile sperm, and concomitant reductions in apoptosis and necrosis. The extract also significantly increased the proportion of sperm with a contiguous plasma membrane and intact acrosome (p < 0.05). Furthermore, LC-MS revealed numerous secondary metabolites in the extract that may contribute to sperm cryopreservation.

Overview on the Antioxidants, Egg Yolk Alternatives, and Mesenchymal Stem Cells and Derivatives Used in Canine Sperm Cryopreservation

Sperm cryopreservation is a widely used assisted reproductive technology for canine species. The long-term storage of dog sperm is effective for the breeding of dogs living far apart, scheduling the time of artificial insemination that suits the female, and preventing diseases of the reproductive tract. However, spermatozoa functions are impaired during the freeze-thaw processes, which may decrease reproductive performance. Numerous attempts have been made to restore such impairments, including the use of cryoprotectants to prevent the damage caused by ice crystal formation, and supplementation of antioxidants to reduce reactive oxygen species generation due to osmotic stress during the procedure. Egg yolk derivatives, antioxidants, and, more recently, mesenchymal stem cells (MSCs) and their derivatives have been proposed in this research field. This review article will summarize the current literature available on the topic.

Is addition or removal of seminal plasma able to compensate for the dilution effect of buffalo semen?

The present study aimed to compensate dilution effect using additional seminal plasma (SP) in conventional (80 million (M) spermatozoa/ml) dose and low spermatozoa/dose (8M spermatozoa/ml). We also attempted to confirm whether removal of SP before the extension of ejaculates affects post-thaw sperm quality of buffalo semen. For this, semen ejaculates (N = 15) were divided into four groups: control (CON), removal of SP by centrifugation (NSP), resuspension of the centrifuged semen pellet into SP (CEN) and extra supplementation of SP (ESP). All groups were diluted into two different semen doses to 20 and 2M spermatozoa/0.25 ml using tris egg yolk extender and subsequently cryopreserved. We found that neither addition nor removal of SP affected sperm motility, kinematics, longevity, mitochondrial superoxide production and high mitochondrial membrane potential (MMP). Further, the addition or removal of SP was not able to compensate dilution effect in 2M groups resulting in a significantly (p < .05) reduction in sperm motility, kinematics, sperm longevity, membrane integrity, MMP, and an increase production of mitochondrial superoxide. In conclusion, it appears that role of SP in the sperm cryopreservation process is insignificant.

Effect of Bovine Serum Albumin Supplementation in Tris-Soybean Lecithin-Based Extender on Quality of Chilled Ram Epididymal Spermatozoa

Objective: This study was designed to assess the effects of using tris-soybean lecithin (TSL)-based extender supplemented with bovine serum albumin (BSA) on the quality of ram epididymal spermatozoa during refrigerated storage. Method: Epididymal sperm were collected from 22 Zandi rams, diluted in TSL-based extender at different concentrations (0%, 2.5%, 5%, 7.5%, and 10%) of BSA, and stored for 5 days at 4°C. Sperm parameters including motility, viability, plasma membrane integrity, chromatin protamination, and malondialdehyde (MDA) content were evaluated at 0, 24, 72, and 120 hours of refrigeration. Results: The addition of 10% BSA to the extender significantly improved sperm viability at 24 and 120 hours of refrigerated liquid storage (p < 0.05). An enhancement in plasma membrane integrity was observed along with a decrease in MDA level by increasing the concentration of BSA from 0% to 10% (p > 0.05). Sperm motion characteristics were higher in the BSA-free group at 120 hours of preservation (p < 0.05). No statistical difference was found for nuclear protamination between experimental groups (p > 0.05). Conclusion: BSA supplementation in TSL-based extender can preserve the viability of epididymal ram spermatozoa during liquid storage at 4°C.

Cross-species efficacy of a chemically-defined, soy lecithin-based cryomedium for semen banking in imperiled wild felids

Felid semen has historically been frozen using an egg yolk-based cryopreservation medium. However, the use of egg introduces several potential concerns, such as variability in composition, microbial contamination, and regulatory issues. In the present study, our aim was to compare a chemically-defined, soy-based medium (SOY) to a commercial egg yolk-based medium (TEY) for the cryopreservation of sperm in four imperiled small cat species. Semen was collected from adult male cats (n = 6 black-footed cats; n = 6 sand cats; n = 4 fishing cats; and n = 7 Pallas' cats) via electroejaculation, split into two aliquots, and cryopreserved in SOY or TEY. Frozen-thawed samples were evaluated for sperm motility and rate of progressive motility (up to 24 h post-thaw) and acrosome status (0 and 6 h). No difference in post-thaw traits were observed between treatments in all four species. Heterologous IVF using oocytes collected laparoscopically from domestic cats demonstrated no difference among freezing treatments in percentage of mature oocytes that cleaved or the mean number of blastomeres at 48 h post-insemination. More spermatozoa frozen with SOY were bound to the zona pellucida in the sand cat (P = 0.018), but no treatment effect was observed in the other three species. These findings collectively demonstrate that SOY may be a preferable alternative to TEY for sperm cryopreservation in these four wild felid species.

Male fertility preservation-Methods, indications and challenges

Male fertility preservation has been steadily increasing over the past two decades. Significant improvements have been achieved in the treatment modalities of cancer and other severe chronic medical conditions, leading to an increase in patient survivorship and the resulting demand for future parenthood. Recognition and proper patient counselling before commencing therapies with a potential gonadotoxic effect are of paramount importance. Similarly, nonmedically indicated fertility preservation is on the rise. Social sperm banking, gender dysphoria prior to affirmation procedures and posthumous reproduction preservation are becoming more common. When timing and logistics are appropriate, sperm cryopreservation is considered the gold standard for fertility preservation. Testicular tissue and spermatogonial stem cell autotransplantation is considered experimental and represents a promising alternative for pre-pubertal patients. The current paper aims to review the recent trends in male fertility preservation, the common indications for sperm cryopreservation, techniques for sperm retrieval and experimental frontiers.

Improving the quality of cryopreserved goat semen with a commercial bull extender supplemented with resveratrol

The purpose of the current study was to evaluate the effects of resveratrol (RSV) on the quality of frozen-thawed goat sperm. Semen samples from four bucks were divided into five aliquots and diluted with a commercial bull semen extender containing: no antioxidant (RSV-0, control), 10 μM RSV (RSV-10), 50 μM RSV (RSV-50), 100 μM RSV (RSV-100) and 250 μM RSV (RSV-250). After thawing, sperm motility, abnormal morphology, membrane and acrosome integrity, mitochondrial activity, phosphatidylserine (PS) distribution, and oxidative stress were evaluated. The results indicated that in comparison with the control, when the concentration of RSV was 10 or 50 μM, the total motility, progressive motility, membrane and acrosome integrity, and mitochondrial activity of post-thaw spermatozoa was greater (P < 0.05). Additionally, the use of extenders containing RSV-10 or RSV-50 resulted in a greater percentage of viable spermatozoa as compared to the other groups (P < 0.05). Importantly, there were more viable spermatozoa (49.61 ± 0.61%) and less non-viable spermatozoa (49.16 ± 1.01%) in the RSV-50 group compared to the other extenders (P < 0.05). Furthermore, the use of the extenders containing RSV-10 and -50 resulted in a reduction in ROS production in frozen-thawed spermatozoa as compared to the control (P < 0.05). There, however, was no difference among extenders for abnormal morphology and PS distribution. In conclusion, supplementation with RSV, at a concentration of 10 or 50 μM in the semen extender, can improve the post-thaw goat sperm quality, which may occur as a consequence of inhibition of ROS generation.

Effects of CoQ10 on the quality of ram sperm during cryopreservation in plant and animal based extenders

The purpose of this study was to evaluate the effect of different concentrations of CoQ10 in soybean lecithin (SL) or egg yolk (EY) extenders on ram semen cryopreservation. Semen samples were collected from five rams, twice a week, then diluted in the extenders (SL and EY) containing different concentrations of CoQ10 as follows: extender containing SL: 0 μM (control, SL/Q0), 1 μM (SL/Q1), 2 μM (SL/Q2), 5 μM (SL/Q5) and 10 μM (SL/Q10) CoQ10; extender containing EY: 0 μM (control, EY/Q0), 1 μM (EY/Q1), 2 μM (EY/Q2), 5 μM (EY/Q5) and 10 μM (EY/Q10) CoQ10. Sperm motion characteristics, membrane integrity, abnormal morphology, viability, apoptotic-like changes, mitochondria active potential, acrosome integrity and lipid peroxidation were evaluated after freeze-thaw process. The SL/Q1, SL/Q2, EY/Q1 and EY/Q2 resulted in greater (P ≤ 0.05) sperm total motility, progressive motility, membrane integrity and mitochondria active potential compared to the other groups. Acrosome integrity in the SL/Q0, SL/Q1, SL/Q2, EY/Q0, EY/Q1 and EY/Q2 groups was greater (P ≤ 0.05) than in the SL/Q5, SL/Q10, EY/Q5 and EY/Q10 groups. The SL/Q2 and EY/Q2 treatment groups had greater (P ≤ 0.05) sperm viability rates and less apoptotic-like changes and lipid peroxidation. The CoQ10 compound could be explored as a novel potential antioxidant for cryopreservation of ram semen because with used of this compound in the present study there was an improved post-thawed sperm quality.

Efficacy of soy-lecithin for replacing egg yolk in tris extender on quality of frozen buck semen

The present study undetaken to find the efficacy of incorporating soy-lecithin in tris extender for replacing egg yolk, a widely used animal component. Pooled ejaculates (40), 10 from each of four bucks maintained at Goat Research Station, Burnihat were used for freezing in tris extender containing 1% and 1.5% soy-lecithin and 20% egg yolk by adopting split sample technique following conventional method. The post thaw sperm motility in 1.5% soy-lecithin-tris extender (60.20±0.45%) was comparable with that of 20% egg yolk-tris (61.20±0.45%), the difference being non-significant. However, the post thaw values for live sperm, intact acrosome and hypo-osmotic swollen sperm were significantly lower in 1.5% soy-lecithin-tris as compared to that in 20% egg yolk-tris. The post thaw values were significantly higher for 1.5% than that for 1% soy-lecithin for all the parameters studied. It could be concluded that 1.5% soy-lecithin-tris extender has similar efficacy with that of 20% egg yolk-tris extender in respect of post thaw sperm motility; however, significantly lower post thaw values for remaining sperm qualities obtained with soy-lecithin in tris-based extender necessitate further trials comprising higher number of ejaculates from more bucks to find a suitable level of soy-lecithin for replacing egg yolk in tris extender for freezing of goat semen.

Effect of addition of melatonin on liquid storage of ram semen at 4°C

Adding a certain amount of antioxidants to semen extender has been shown to improve semen quality. The aim of present study was to elucidate whether the supplementation of melatonin to the Tris-based extender (CTR) could enhance the quality of ram spermatozoa during storage at 4°C. Ram semen samples were collected and diluted with CTR extender containing different concentrations (0, 0.05 (M 0.05), 0.1 (M 0.1), 0.2 (M 0.2) or 0.4 (M 0.4) mM) of melatonin. Sperm routine indicators, mitochondrial activity, total antioxidant capacity (T-AOC) and malondialdehyde (MDA) content were analysed in control and melatonin treatment groups. The higher per cent of motility, plasma membrane integrity, mitochondrial activity and T-AOC activity was observed in M 0.05, M 0.1 and M 0.2 groups compared to control group at 5 days of storage (p < 0.05), while lower percentage of MDA content was observed among these groups (p < 0.05). In addition, there were no significant differences in acrosome integrity among the control and M 0.05, M 0.1 and M 0.2 groups during the experiment. The above results show that the addition of 0.05, 0.1, 0.2 mM of melatonin is beneficial to the preservation of ram semen during liquid storage at 4°C mainly through antioxidative stress.

Comparison Between an Animal-Derived Product Medium and a Chemically Defined Medium for Ram Sperm Cryopreservation

Animal-derived products are widely used in sperm cryopreservation for their cryoprotective properties. These components, however, tend to be replaced because of sanitary risks. STEMALPHA.CRYO3 (Ref. 5617; Stem Alpha, Saint-Genis-l'Argentière, France), called "CRYO3," is a chemically defined preservation medium currently used for freezing human tissue and adult stem cells. The aim of this study was to evaluate the effect of a CRYO3-based medium on ram sperm freezing regarding in vitro parameters and in vivo fertility. Semen from nine Charolais rams was collected using an artificial vagina, then split and frozen using two media: a CRYO3-based medium or a control medium containing egg yolk (10%) and milk (45%). Sperm membrane integrity (propidium iodide [PI]/SYBR-14 and calcein AM/ethidium homodimer-1), acrosome integrity (FITC-PNA/PI), and mitochondrial membrane potential (JC-1) were assessed using flow cytometry, while functional membrane integrity was assessed using a hypo-osmotic swelling test and motility parameters, evaluated by computer-assisted sperm analysis. Pregnancy rates, prolificacy, and the average daily weight gain (DWG) of lambs were evaluated after performing 195 laparoscopic inseminations. The control medium showed significantly higher results than CRYO-based medium for all in vitro parameters, except for linearity and straightness (motions parameters). Conversely, field trials showed no significant difference between the control medium and the CRYO3-based medium for pregnancy rates (72.2% and 67.9%, respectively), prolificacy (1.8 and 1.6, respectively), and the DWG (0.34 and 0.35 kg/d, respectively). This preliminary study showed that CRYO3 cannot replace egg yolk and milk in freezing extenders for commercial purposes. However, as laparoscopic inseminations allowed a 67% pregnancy rate, CRYO3-based medium remains an option for international transport or long-term storage of genetic diversity.

Effect of egg yolk plasma and soybean lecithin on rooster frozen-thawed sperm quality and fertility

This experiment was conducted to study the effects of egg yolk plasma (10%, 15% and 20%), soybean lecithin (0.5%, 1% and 1.5%) and whole egg yolk (WEY) (control) on post-thawed sperm quality, hatchability and fertility outcomes. In experiment 1, sperm motility, abnormalities, membrane integrity, viability, apoptosis status, mitochondrial activity were studied following freeze-thawing. The best quality of frozen-thawed rooster sperm was chosen to be used for the assessment of the hatchability and fertility rate in experiment 2. The significantly higher percentages of post-thawing sperm total and progressive sperm motilities, membrane integrity, viability were observed in 1% soybean lecithin and 20% egg yolk plasma in comparison with 0.5 and 1% soybean lecithin, 10% egg yolk plasma and control, except for 15% egg yolk plasma (P < 0.05). Using 20% egg yolk plasma in the extender improved mitochondrial activity. Supplementation of 1% soybean lecithin and 20% egg yolk plasma into the extender resulted in the least percentages of dead sperm (P < 0.05). Sperm abnormalities and early apoptosis did not differ in various extender supplementations. In experiment 2, higher percentages of hatchability and fertility rate were observed in semen containing 1% soybean lecithin and 20% egg yolk plasma compared with the WEY group. The results showed that supplementation of the rooster sperm extender with 1% soybean lecithin and 20% egg yolk plasma resulted in higher quality of frozen-thawed sperm.

Ram semen deterioration by short-term exposure to high altitude is prevented by improvement of antioxidant status

Ovine reproduction efficiency in herds at high altitude (ha) is lower than that at low altitude (la). In ewes, ha effects are due to hypoxia and oxidative stress. Our aim was to establish the effect of antioxidant vitamin supplementation on semen traits and antioxidant status of rams exposed to short or long time ha. A total of 32 rams native to la (~500 m) were used, 16 were kept at la and the other 16 were brought to ha (~3600 m), where they were placed in the same flock as the ha native rams (n=16). Half of the animals in each group were supplemented daily with vitamins C 600 mg and E 450 IU per os, during the entire experimental period, starting the 4th day after animal's arrival at ha (day 0). At days 0, 30 and 60 of treatment, blood and semen samples were collected for evaluation of antioxidant status and semen standard characteristics. Data were compared within each experimental time by analysis of variance using a general linear model. Elevated concentrations of oxidative stress biomarkers were present in blood from animals maintained at ha. Ejaculates from ha exposed rams showed decreased sperm concentration, progressive motility and viability, in addition to decreased antioxidant status in seminal fluid. A total of 30 days of oral supplementation with vitamins C and E prevented some ha negative effects on semen characteristics, mainly in recently ha exposed rams. It is concluded that exposure of rams to ha negatively affects semen quality, where oxidative stress plays a predominant role. These effects are mainly prevented by oral supplementation of vitamins C and E, which constitutes a simple and cheap alternative to improve semen quality of rams when they are moved to ha.

Fertility response of artificial insemination methods in sheep with fresh and frozen-thawed semen

The aim of this study was to evaluate the fertility response of artificial insemination (AI) methods with fresh and frozen sperm in sheep. In experiment 1, one hundred and fifty fat tailed Zandi ewes were assigned into 3 equal groups and inseminated with three AI methods consisting of vaginal, laparoscopic and trans-cervical AI with fresh semen. In experiment 2, a factorial study (3 AI methods × 2 extenders) was used to analyze the effects of three AI methods and two freezing extenders containing soybean lecithin (SL) or Egg yolk (EY) on reproductive performance of 300 fat tailed Zandi ewes. Also, total motility, progressive motility, viability and lipid peroxidation of semen were evaluated after freeze-thawing in two extenders. In result, there was no significant difference among three AI methods when fresh semen was used. In experiment 2, the highest percentage of pregnancy rate, parturition rate and lambing rate were obtained in laparoscopic AI group (P < 0.05). Although pregnancy rate, parturition rate and lambing rate in trans-cervical group were higher (P < 0.05) than vaginal group, the results were not as high as laparoscopic group. No difference was observed between SL and EY extenders and their performance was close to each other. It can be concluded that although no difference was observed on reproductive performance for fresh semen, trans-cervical AI was more efficient than vaginal method when frozen-thawed semen was used, but its efficiency was not as high as laparoscopic method. Also, SL extender can be an efficient alternative extender to preserve ram sperm during cryopreservation procedure without adverse effects of EY.

Effect of dietary fish oil supplementation on ram semen freeze ability and fertility using soybean lecithin- and egg yolk-based extenders

Ram semen cryopreservation is not efficient for artificial insemination in commercial herds. Beneficial effects of dietary fish oil have been evaluated for cryopreservation of ram semen in soybean lecithin (SL) and egg yolk (EY)-based extenders. A factorial study (two diets × two extenders) was used to analyze the effects of two diets supplemented with fish oil (n-3 fatty acid) or palm oil (saturated fatty acids; [SFAs]) to freeze ram semen in two extenders containing SL or EY. Motility characteristics, membrane integrity, abnormal morphology, mitochondria activity, acrosome integrity, apoptotic status, and fertilizing ability were assessed after freeze-thawing. Although diet had significant (P ≤ 0.05) effects on the quality parameters of frozen-thawed sperm, effects of extenders on these traits were not significant (P > 0.05). The higher significant (P ≤ 0.05) percentage of total motility and progressive motility were observed in n-3/SL (44.83 ± 1.56 and 28.33 ± 1.4) and n-3/EY (43.33 ± 1.56 and 28.50 ± 1.4) than SFA/SL (32.16 ± 1.56 and 14.00 ± 1.4) and SFA/EY (31.66 ± 1.56 and 12.66 ± 1.4) groups. Moreover, n-3/SL and n-3/EY produced the higher significant (P ≤ 0.05) percentage of membrane integrity of sperm (39.83 ± 1.4 and 37.33 ± 1.4) than SFA/SL and SFA/EY (29.83 ± 1.4 and 28.5 ± 1.4). For viability results, the higher significant percentage of live sperm was observed in n-3/SL and n-3/EY (43.16 ± 1.38 and 45.66 ± 1.38) than SFA/SL and SFA/EY (28.66 ± 1.38 and 27.5 ± 1.38). For fertility trials, n-3-based diets (n-3/SL and n-3/EY) improved significantly (P ≤ 0.05) pregnancy rate (44% and 46%), parturition rate (42% and 42%), and lambing rate (46% and 44%) compared with the SFA-based diets (SFA/SL and SFA/EY). No interaction effects have been found between diets and extenders (P > 0.05). It seems that dietary fish oil can improve the semen performance after freezing-thawing process and artificial insemination aside from type of extenders.

Fertility and flow cytometry study of frozen-thawed sperm in cryopreservation medium supplemented with soybean lecithin

Semen cryopreservation can provide genetic resources for a large number of females from a small number of superior males. Optimization of cryopreservation media to achieve the highest quality of post-thaw semen is crucial. Soybean lecithin has evaluated as a plant-based cryoprotectant for substitution of egg yolk in ram semen extender. Flow cytometric and fertility assessments were applied following cryopreservation procedure in two experimental groups (SL group: extender containing 1% w/v soybean lecithin and EY group: extender containing 20% v/v egg yolk). The higher percentage of live sperm and the lower percentage of dead sperm were obtained in SL (47.66 ± 1.38, 52.33 ± 1.69, respectively) extender compared to EY (41.16 ± 1.38, 58.83 ± 1.69). For motion characteristics, plasma membrane integrity, acrosome integrity and mitochondria activity, no significant difference was observed between SL and EY extenders. In artificial insemination experiment, there was no significant difference in pregnancy rate, lambing rate and twining rate between SL and EY extenders. It can be concluded that SL extender can be an efficient alternative extender to preserve ram sperm during cryopreservation procedure without adverse effects.

Cryopreservation of ram semen with antioxidant supplemented soybean lecithin-based extenders and impacts on incubation resilience

The scope of this study was investigation the affects of various antioxidants on 1% soybean lecithin-based semen extenders for ram semen cryopreservation. Ejaculates, collected via electrically stimulated ejaculation, that have a thick consistency, rapid wave motion (3-5 on a 0-5 scale) and >75% initial motility were pooled. The pooled samples were split into four equal aliquots as 5 mM Methionine, 5 mM Cysteamine, 1 mM Cysteine and a sample of antioxidant-free control group. Each sample group was diluted to a ratio of 1/5 (semen/extender, v/v) as final concentration and two step dilution method was used for cryopreservation. Extender groups were assessed for sperm motility, plasma membrane functional integrity using hypoosmotic swelling test (HOST), damaged acrosome using FITC-Pisum sativum agglutinin (PSA-FITC) and DNA integrity using terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling (TUNEL). Semen samples also incubated for 6 h in humidified air with 5% CO2 at 39 °C to evaluate post-thaw incubation resilience of semen characteristics. The results showed that freezing and thawing procedures had negative effects on motility (P < 0.05), plasma membrane integrity (P < 0.05) and acrosomal integrity (P < 0.05). After 6 h of incubation time, the Cysteine supplemented extender group yielded significantly higher results than other extender groups in terms of spermatological parameters. Furthermore MDA levels in the antioxidant groups were lower than control group (P < 0.05). Nevertheless, there were no significant differences among antioxidant groups.

Comparison of various semen extenders and addition of prostaglandin F2α on pregnancy rate in cows

This investigation comprises three trials. Trial 1 consists of an in vitro comparison of three semen extenders: two egg yolk based (customized Tris-egg yolk-glycerol and Triladyl®), the third (AndroMed®) soybean lecithin based. With regard to post-thaw motility, the phytoextender AndroMed® proved to be superior (59±3% v. 53±2% and 53±2%, P<0.05). It had earlier been shown that addition of the commercial prostaglandin F2α preparation Dinolytic® before freezing compromises post-thaw motility; therefore, in Trial 2, Dinolytic® was added after thawing. Frozen-thawed spermatozoa tolerated addition of Dinolytic® at a concentration of 30% (v/v). In Trial 3, cows were inseminated using straws in which diluted semen and Dinolytic® were frozen in the same straw, separated by an air bubble, so intermingling could only take place in the course of insemination. Pregnancy rates at Dinolytic® dosages of 0%, 30% or 60% amounted to 44%, 41% and 56%, respectively (P>0.05), a result that encourages a large-scale field study, which is envisioned.

Successful ram semen cryopreservation with lyophilized egg yolk-based extender

The aim of this study was to evaluate the effects of lyophilized egg yolk extender on ram semen cryopreservation. Ejaculates with a thick consistency, rapid wave motion (3-5 on a 0-5 scale) and >75% initial motility were pooled. Sperm were diluted to final concentration of 1/5 (semen/extender) in lyophilized egg yolk or fresh egg yolk extenders using two-step dilution method. The equilibrated semen was frozen in 0.25 mL straws. Semen samples were assessed for sperm motility, plasma membrane functional integrity using hypoosmotic swelling test (HOST), damaged acrosome using FITC-Pisum sativum agglutinin (PSA-FITC) and DNA integrity using terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling (TUNEL) at three time points: after dilution with extender A, equilibration and post-thaw. The results showed that freezing and thawing procedures (dilution, equilibration and thawing) had negative effects on motility (P<0.001), plasma membrane integrity (P<0.001), acrosome integrity (P<0.001) and DNA integrity (P<0.001). In the study, there were no significant differences between lyophilized and fresh egg yolk extenders when comparing motility, plasma membrane integrity, acrosome integrity and DNA integrity between groups. In conclusion, lyophilized egg yolk extender provided similar cryoprotective effects with fresh egg yolk extender to cryopreserve ram semen.

Beneficial Effects of Nitric Oxide Induced Mild Oxidative Stress on Post-Thawed Bull Semen Quality

Background

Cryopreservation of semen requires optimized conditions to minimize the harmful effects of various stresses. The main approach for protection of sperm against stress is based on the use of antioxidants and cryoprotectants, which are described as defensive methods. Recently, the application of controlled mild stressors has been de- scribed for activation of a temporary response in oocyte, embryo and somatic cells. In this study a sub-lethal oxidative stress induced by precise concentrations of nitric oxide (NO) has been evaluated for sperm during cryopreservation.

Materials and Methods

In this experimental study, we used different concentrations of NO [0 µM (NO-0), 0.01 µM (NO-0.01), 0.1 µM (NO-0.1), 1 µM (NO-1), 10 µM (NO-10) and 100 µM (NO-100)] during cryopreservation of bull semen. Their effects on post-thawed sperm quality that included motility and velocity parameters, plasma mem- brane functionality, acrosome integrity, apoptosis status, mitochondrial activity and lipid peroxidation after freezing-thawing were investigated.

Results

Exposure of sperm before freezing to NO-1 significantly increased total motility (88.4 ± 2.8%), progressive motility (50.4 ± 3.2%) and average path velocity (VAP, 53.8 ± 3.1 µm/s) compared to other extenders. In addition, NO-1 significantly increased plasma mem- brane functionality (89.3 ± 2.9%) compared to NO-0 (75.3 ± 2.9%), NO-0.01 (78.3 ± 2.9%), NO-0.1 (76.4 ± 2.9%), NO-10 (64 ± 2.9%) and NO-100 (42 ± 2.9%). Sperm exposed to NO-1 produced the highest percentage of viable (85.6 ± 2.3%) and the lowest percentage of apoptotic (10.8 ± 2.4%) spermatozoa compared to the other extenders. Also, NO-100 resulted in a higher percentage of dead spermatozoa (27.1 ± 2.7%) compared to the other extenders. In terms of mitochondrial activity, there was no significant difference among NO-0 (53.4 ± 3.2), NO-0.01 (52.1 ± 3.2), NO-0.1 (50.8 ± 3.2) and NO-1 (53.1 ± 3.2). For acrosome integrity, no significant different was observed in sperm exposed to different concentrations of NO.

Conclusion

Induction of sub-lethal oxidative stress with 1 µM NO would be beneficial for cryopreservation of bull semen.

Motility and fertility of rabbit sperm cryopreserved using soybean lecithin as an alternative to egg yolk

This study was conducted to investigate whether soy lecithin can be used as an alternative cryoprotectant to establish a procedure that does not require the use of egg yolk to cryopreserve rabbit strains. Semen from Japanese White rabbits was frozen with HEPES extender containing 20% egg yolk (EYH), 0.5% (Lec-0.5), 1.5% (Lec-1.5), 2.5% (Lec-2.5), or 3.5% (Lec-3.5; wt/vol) lecithin (type IV-S, ≥30%), and the motility of thawed sperm was analyzed. The sperm motility in the Lec-1.5 group was significantly higher than that in the Lec-2.5 and 3.5 groups and equivalent to the EYH group. From 17 rounds of artificial insemination with frozen-thawed sperm in the EYH and Lec-1.5 groups, 12 rabbits in both groups were pregnant (70.6%) and delivered offspring. The litter size was 3.3 in the EYH group and 5.1 in the Lec-1.5 group. These results indicate that soy lecithin can be used as a substitute for egg yolk as a cryoprotectant on the basis of motility and fertility of the frozen-thawed rabbit sperm and that 1.5% lecithin (type IV-S, ≥30%) in the semen extender was the optimum concentration for rabbit sperm cryopreservation.