Implications of cryopreservation on structural and functional attributes of bovine spermatozoa: An overview

Cryoprotective Potential of Theobromine in the Improvement of the Post-Thaw Quality of Bovine Spermatozoa

Theobromine (TBR) is a methylxanthine known for its bronchodilatory and stimulatory effects. This research evaluated the vitality, capacitation patterns, oxidative characteristics, microbial profile and expression of capacitation-associated proteins (CatSper1/2, sodium bicarbonate cotransporter [NBC], protein kinases A [PKA] and C [PKC] and adenylate cyclase 10 [ADCY10]) in cryopreserved bovine spermatozoa (n = 30) in the absence (cryopreserved control [CtrlC]) or presence of different TBR concentrations (12.5, 25, and 50 µM) in egg yolk extender. Fresh ejaculate served as a negative control (CtrlN). Significant post-thaw maintenance of the sperm motility, membrane and DNA integrity and mitochondrial activity (p < 0.001) were recorded following the administration of 25 μM and 50 μM TBR, then compared to CtrlC. All groups supplemented with TBR exhibited a significantly lower percentage of prematurely capacitated spermatozoa (p < 0.001) than CtrlC. Significantly decreased levels of global reactive oxygen species (ROS), hydrogen peroxide and hydroxyl radicals were observed in the presence of 25 μM and 50 μM TBR (p < 0.01). Western blot analysis revealed that supplementation with 50 μM TBR significantly prevented the loss of NBC and ADCY10 (p < 0.01), while all TBR doses stabilized the levels of PKC (p < 0.05 at 50 μM TBR; p < 0.001 at 12.5 μM and 25 μM TBR). In summary, we suggest that TBR is effective in protecting the spermatozoa during the cryopreservation process through its potential to stimulate energy synthesis while preventing ROS overproduction and the loss of proteins involved in the sperm activation process.

Effect of naringenin on post-thaw quality, fertility-associated gene expression and fertilization potential of buffalo (Bubalus bubalis) bull sperm

Our objectives were to explore the effect of naringenin addition in the semen extender on the post-thaw 1) sperm quality, 2) fertility-associated gene expression, and 3) fertilization potential of buffalo bull sperm. In experiment 1, semen samples (n = 32) from four Nili-Ravi buffalo bulls were pooled (n = 8) and diluted with the tris-citric acid (TCF-EY) extender containing different concentrations of naringenin, i.e., placebo (DMSO), 0 (control), 50, 100, 150 and 200 μM naringenin. After dilution, semen samples were packed in 0.5 mL French straws, cryopreserved and analyzed for post-thawed sperm quality and gene expression. Computer-assisted Semen Analysis, Hypo-osmotic Swelling test, Normal Apical Ridge assay, Rhodamine 123, Acridine orange, Propidium iodide staining and Thiobarbituric Acid Reactive Substances assay were performed to assess sperm motility parameters, plasma membrane functionality, acrosome integrity, mitochondrial membrane potential, DNA integrity, viability and lipid peroxidation, respectively. Expression levels of sperm acrosome-associated SPACA3, DNA condensation-related PRM1, anti-apoptotic BCL2, pro-apoptotic BAX, and oxidative stress-associated ROMO1 genes were evaluated through qPCR. Results revealed that total and progressive motility, plasma membrane functionality, acrosome integrity, mitochondrial membrane potential, DNA integrity and viability were higher (P < 0.05) with 50, 100 and 150 μM naringenin compared to 200 μM naringenin, placebo and control groups. Moreover, all naringenin-treated groups improved catalase activity, and reduced lipid peroxidation compared to placebo and control groups (P < 0.05). Relative expression levels of SPACA3 and PRM1 genes were higher (P < 0.05) with 150 μM naringenin compared to all groups except 100 μM (P > 0.05). No difference (P > 0.05) in the expression level of BCL2 gene was observed among all groups. Furthermore, BAX gene was expressed higher (P < 0.05) in the 200 μM naringenin group, whereas no difference (P > 0.05) in expression was noticed among the remaining groups. In addition, ROMO1 gene was expressed lower (P < 0.05) in all naringenin-treated groups compared to the control. In experiment 2, the in vivo fertility of semen doses (n = 400; 200/group) containing optimum concentration of naringenin (150 μM; depicted better in vitro sperm quality in experiment 1) was compared with control during the breeding season. Buffaloes were inseminated 24 h after the onset of natural estrus and palpated transrectal for pregnancy at least 60 days post-insemination. The fertility rate of 150 μM naringenin group was higher (P = 0.0366) compared to the control [57.00 ± 0.03 % (114/200) vs. 46.50 ± 0.04 % (93/200), respectively]. Taken together, it is concluded that naringenin supplementation in semen extender improves post-thaw quality, fertility-associated gene expression and fertilization potential of buffalo bull sperm, more apparently at 150 μM concentration.

Thawing of cryopreserved sperm from domestic animals: Impact of temperature, time, and addition of molecules to thawing/insemination medium

In recent decades, there has been a growing interest in optimizing the protocols intended to sperm cryopreservation in domestic animals. These protocols include initial cooling, freezing, and thawing. While different attempts have been devised to improve sperm cryopreservation, the efficiency of this reproductive biotechnology is still far from being optimal. Furthermore, while much attention in improving cooling/freezing, less emphasis has been made in how thawing can be ameliorated. Despite this, the conditions through which, upon thawing, sperm return to physiological temperatures are much relevant, given that these cells must travel throughout the female genital tract until they reach the utero-tubal junction. Moreover, the composition of the media used for artificial insemination (AI) may also affect sperm survival, which is again something that one should bear because of the long journey that sperm must make. Furthermore, sperm quality and functionality decrease dramatically during post-thawing incubation time. Added to that, the deposition of the thawed sperm suspension devoid of seminal plasma in some species during an AI is accompanied by a leukocyte migration to the uterine lumen and with it the activation of immune mechanisms. Because few reviews have focused on the evidence gathered after sperm thawing, the present one aims to compile and discuss the available information concerning ruminants, pigs and horses.

Revisiting the Injury Mechanism of Goat Sperm Caused by the Cryopreservation Process from a Perspective of Sperm Metabolite Profiles

Semen cryopreservation results in the differential remodeling of the molecules presented in sperm, and these alterations related to reductions in sperm quality and its physiological function have not been fully understood. Given this, this study aimed to investigate the cryoinjury mechanism of goat sperm by analyzing changes of the metabolic characteristics in sperm during the cryopreservation process. The ultra-high-performance liquid chromatography-quadrupole time-of-flight mass spectrometry (UHPLC-QTOF-MS) technique was performed to explore metabolite profiles of fresh sperm (C group), equilibrated sperm (E group), and frozen-thawed sperm (F group). In total, 2570 metabolites in positive mode and 2306 metabolites in negative mode were identified, respectively. After comparative analyses among these three groups, 374 differentially abundant metabolites (DAMs) in C vs. E, 291 DAMs in C vs. F, and 189 DAMs in E vs. F were obtained in the positive mode; concurrently, 530 DAMs in C vs. E, 405 DAMs in C vs. F, and 193 DAMs in E vs. F were obtained in the negative mode, respectively. The DAMs were significantly enriched in various metabolic pathways, including 31 pathways in C vs. E, 25 pathways in C vs. F, and 28 pathways in E vs. F, respectively. Among them, 65 DAMs and 25 significantly enriched pathways across the three comparisons were discovered, which may be tightly associated with sperm characteristics and function. Particularly, the functional terms such as TCA cycle, biosynthesis of unsaturated fatty acids, sphingolipid metabolism, glycine, serine and threonine metabolism, alpha-linolenic acid metabolism, and pyruvate metabolism, as well as associated pivotal metabolites like ceramide, betaine, choline, fumaric acid, L-malic acid and L-lactic acid, were focused on. In conclusion, our research characterizes the composition of metabolites in goat sperm and their alterations induced by the cryopreservation process, offering a critical foundation for further exploring the molecular mechanisms of metabolism influencing the quality and freezing tolerance of goat sperm. Additionally, the impacts of equilibration at low temperature on sperm quality may need more attentions as compared to the freezing and thawing process.

Phenomics in Livestock Research: Bottlenecks and Promises of Digital Phenotyping and Other Quantification Techniques on a Global Scale

Bottlenecks in moving genomics to real-life applications also include phenomics. This is true not only for genomics medicine and public health genomics but also in ecology and livestock phenomics. This expert narrative review explores the intricate relationship between genetic makeup and observable phenotypic traits across various biological levels in the context of livestock research. We unpack and emphasize the significance of precise phenotypic data in selective breeding outcomes and examine the multifaceted applications of phenomics, ranging from improvement to assessing welfare, reproductive traits, and environmental adaptation in livestock. As phenotypic traits exhibit strong correlations, their measurement alongside specific biological outcomes provides insights into performance, overall health, and clinical endpoints like morbidity and disease. In addition, automated assessment of livestock holds potential for monitoring the dynamic phenotypic traits across various species, facilitating a deeper comprehension of how they adapt to their environment and attendant stressors. A key challenge in genetic improvement in livestock is predicting individuals with optimal fitness without direct measurement. Temporal predictions from unmanned aerial systems can surpass genomic predictions, offering in-depth data on livestock. In the near future, digital phenotyping and digital biomarkers may further unravel the genetic intricacies of stress tolerance, adaptation and welfare aspects of animals enabling the selection of climate-resilient and productive livestock. This expert review thus delves into challenges associated with phenotyping and discusses technological advancements shaping the future of biological research concerning livestock.

Sperm freezing damage: the role of regulated cell death

Substantial progress in research on sperm cryopreservation has occurred since the twentieth century, especially focusing on improving sperm freezing procedures and optimizing semen extenders. However, the cellular biological mechanisms of sperm freezing damage are still unclear, which greatly restricts the promotion and development of sperm cryopreservation. An essential component of sperm freezing damage is the occurrence of cell death. Considering the existence of multiple types of cell death pathways, this review discusses connections between characteristics of regulated cell death (e.g., apoptosis and ferroptosis), and accidental cell death (e.g., intracellular ice crystals) with sperm freezing damage and explores possible future research directions in this field.

Study on the correlation of supplementation with L-citrulline on the gastrointestinal flora and semen antifreeze performance of ram

Introduction

Cryopreservation of semen can give full play to the reproductive advantages of male animals. However, in actual production, due to the poor frost resistance of sheep semen and the low conception rate, the promotion of sheep frozen semen is greatly hindered. Therefore, it is urgent to improve the frost resistance of semen to improve the quality of frozen semen. At present, most studies on improving the quality of frozen semen are based on the improvement of semen dilutions, and few studies on improving the freezing resistance of ram semen by feeding functional amino acids.

Methods

Therefore, 24 Turpan black rams were divided into high antifreeze group (HF) and a low antifreeze group (LF) Each of these groups was further randomly divided into control and experimental subgroups. The control subgroup was fed a basal diet, while the experimental subgroup received an additional 12 g/d of L-Cit supplementation based on the control group for a duration of 90 days.

Results

The results showed that Following L-Cit supplementation, the experimental group demonstrated significantly elevated sperm density and VSL (Velocity of straight line), T-AOC, GSH-Px, and NO levels in fresh semen compared to the control group (P < 0.01). After thawing, the experimental group exhibited significantly higher levels of T-AOC, GSH-Px, and NO compared to the control group (P < 0.01). Additionally, the HFT group, after thawing frozen semen, displayed significantly higher HK1 protein expression compared to the control group. The number of spermatogonia, spermatocytes, and sperm cells in the HFT group was significantly higher than that in the HFC group. Moreover, 16S rRNA sequence analysis showed that Candidatus_Saccharimonas, Staphylococcus, Weissella, succinivbrionaceae_UcG_002, and Quinella were significantly enriched in the rumen of the HFT group, while Ureaplasma was significantly enriched in the HFC group. In the duodenum, Clostridiales_bacterium_Firm_14, Butyrivibrio, and Prevotellaceae_NK3831_group were significantly enriched in the HFT group, whereas Desulfovibrio and Quinella were significantly enriched in the HFC group.

Discussion

Under the conditions employed in this study, L-Cit supplementation was found to enhance the intestinal flora composition in rams, thereby improving semen quality, enhancing the antifreeze performance of semen, and promoting the development of testicular spermatogenic cells.

Seminal cell-free DNA as a potential marker for in vitro fertility of Nellore bulls

PURPOSE

This study aimed to identify a marker for freezability and in vitro fertility of sperm samples before freezing.

METHODS

Semen was collected from nine Nelore bulls; half of the ejaculate was used for seminal plasma cell-free DNA (cfDNA) quantification, and the other half was cryopreserved. Evaluation of sperm movement using computer-assisted semen analysis and plasma membrane integrity and stability, acrosomal integrity, apoptosis, and mitochondrial potential using flow cytometry were performed on fresh and frozen/thawed semen at 0, 3, 6, and 12 h after thawing. Frozen/thawed sperm was also used for in vitro embryo production. cfDNA was extracted from each bull, and the total DNA and number of cell-free mitochondrial DNA (cfmtDNA) copies were quantified. Semen from each animal was used for IVF, and cleavage, blastocyst formation, and cell counts were evaluated.

RESULTS

Two groups were formed and compared based on the concentrations of cfDNA and cfmDNA present: low-cfDNA and high-cfDNA and low-cfmtDNA and high-cfmtDNA. Up to 12 h post-thawing, there were no differences between the groups in the majority of the sperm parameters evaluated. Cleavage, day 6 and 7 blastocyst rates, and the number of cells were higher in the high cfDNA group than in the low cfDNA group. Similar results were observed for cfmtDNA, except for the number of cells, which was similar between the groups.

CONCLUSION

The concentration of cfDNA and the relative number of copies of cfmtDNA in seminal plasma cannot predict the freezability of semen but can be used to predict in vitro embryo production.

The association of resveratrol and AFPI did not enhance the cryoresistance of ram sperm

Cryoprotectants are required to reduce damage caused to the cells due to low temperatures during the cryopreservation. Antifreeze proteins (AFP) have a well-known role in cell membrane protection, while resveratrol is a potent antioxidant. This study assessed the effect of the association of resveratrol concentrations and AFP I in a ram semen extender. Pooled semen of four rams was allocated into six treatments in a factorial arrangement: (CONT, only the semen extender); only AFP I (ANT: 0.1 µg/mL of AFP I), only resveratrol, one treatment with two levels (10 µM/mL or 50 µM/mL of resveratrol); and two treatments with the interactions, with one AFP I and one of the two levels of resveratrol (0.1 µg/mL of AFP I with 10 µM/mL resveratrol; 0.1 µg/mL of AFP I with 50 µM/mL resveratrol). No interaction between factors was observed on sperm kinetics, plasma membrane integrity, hypo-osmotic test, and mitochondrial activity parameters. There was a high probability (P = 0.06) of reducing sperm cells with functional membrane percentage in the hypo-osmotic test and increasing the percentage of sperm with high mitochondrial activity (P = 0.07) was observed in AFP presence. An interaction of AFP and resveratrol was observed in non-capacitated sperm (P = 0.009), acrosomal reaction (P = 0.034), and sperm binding (P = 0.04). In conclusion, the association of resveratrol and AFP did not improve the quality of frozen-thawed semen and even promoted deleterious effects compared to their single addition in the semen extender. The supplementation of 50 µM/mL of resveratrol improved the outcomes of frozen-thawed ram sperm, being a potential cryoprotectant.

Risk of Sperm Disorders and Impaired Fertility in Frozen-Thawed Bull Semen: A Genome-Wide Association Study

Cryopreservation is a widely used method of semen conservation in animal breeding programs. This process, however, can have a detrimental effect on sperm quality, especially in terms of its morphology. The resultant sperm disorders raise the risk of reduced sperm fertilizing ability, which poses a serious threat to the long-term efficacy of livestock reproduction and breeding. Understanding the genetic factors underlying these effects is critical for maintaining sperm quality during cryopreservation, and for animal fertility in general. In this regard, we performed a genome-wide association study to identify genomic regions associated with various cryopreservation sperm abnormalities in Holstein cattle, using single nucleotide polymorphism (SNP) markers via a high-density genotyping assay. Our analysis revealed a significant association of specific SNPs and candidate genes with absence of acrosomes, damaged cell necks and tails, as well as wrinkled acrosomes and decreased motility of cryopreserved sperm. As a result, we identified candidate genes such as POU6F2, LPCAT4, DPYD, SLC39A12 and CACNB2, as well as microRNAs (bta-mir-137 and bta-mir-2420) that may play a critical role in sperm morphology and disorders. These findings provide crucial information on the molecular mechanisms underlying acrosome integrity, motility, head abnormalities and damaged cell necks and tails of sperm after cryopreservation. Further studies with larger sample sizes, genome-wide coverage and functional validation are needed to explore causal variants in more detail, thereby elucidating the mechanisms mediating these effects. Overall, our results contribute to the understanding of genetic architecture in cryopreserved semen quality and disorders in bulls, laying the foundation for improved animal reproduction and breeding.

Rapid thawing of frozen bull spermatozoa by transient exposure to 70 °C improves the viability, motility and mitochondrial health

Up to now, the definitive conclusion of the positive effects of rapid transient thawing at higher temperatures for shorter durations has not been obtained yet and is still under discussion due to some contradictory findings and limited assessment of post-thawed parameters. The purpose of the current study was to evaluate the effectiveness of rapid thawing in water at 70 °C by using various post-thawed parameters of frozen bull spermatozoa. Experiment 1, monitoring the change of temperature inside frozen bull straw thawed in water at different temperatures. Experiment 2, evaluation of various post-thawed characteristics of frozen bull spermatozoa thawed in water at different temperatures by using a computer-assisted sperm analysis, flow cytometry and immunocytochemistry. The time it took for the temperature inside the straw to warm up to 15 °C was nearly twice as faster when the straw was thawed in 70 °C water compared with 39 °C. Although there were differences among bulls, viability, motility, and mitochondrial membrane potential of spermatozoa thawed at 70 °C for 8 seconds and stabilized at 39 °C for 52 seconds were significantly higher than those of controls (thawed at 39 °C for 60 seconds) at 0 and 3 h after thawing. Just after thawing, however, there were no differences in acrosome integrity and distribution of phospholipase C zeta1, whereas mitochondrial reactive oxygen species production was significantly lower in spermatozoa thawed at 70 °C. From these results, we conclude that rapid thawing at 70 °C and then stabilization at 39 °C significantly improves viability, motility and mitochondrial health of bull spermatozoa rather than conventional thawing at 39 °C. The beneficial effect of rapid transient thawing could be due to shorter exposure to temperatures outside the physiological range, consequently maintaining mitochondrial health.

Study of mitochondrial function in thawed bull spermatozoa using selective electron transfer chain inhibitors

Bull spermatozoa depend equally on glycolysis and oxidative phosphorylation for the maintenance of the energy necessary for their proper functioning. The aim of the present work was to delineate the mitochondrial activity of bull spermatozoa after incubation with specific inhibitors of the different mitochondrial complexes and evaluate their ROS production. Thawed bull sperm cells (30 × 106 mL-1 in Tyrode's extender) were incubated 1 and 3h at 37 °C with rotenone 5 μM (ROT), complex I inhibitor; dimethyl-malonate 10 mM (DMM), complex II inhibitor; carbonyl cyanide m-chlorophenyl hydrazine 5 μM (CCCP), uncoupling agent; antimycin A 1 μg/mL (ANTI), complex III inhibitor; oligomycin 5 μM (OLIGO), ATP synthase inhibitor, and 0.5% DMSO, vehicle (CTR). Sperm motility and kinematics were assessed by Hamilton Thorn IVOS 12.0. Mitochondrial membrane potential, mitochondrial O2•- production and H2O2 intracellular content were evaluated by BD FACSCalibur flow cytometer, and sperm viability (SYBR-14/PI) and mitochondrial activity (JC-1/SYBR-14/PI) were assessed by epifluorescence microscopy. A multivariate analysis was performed on the results. In addition, sperm kinematic features, registered for each motile spermatozoon, were studied by cluster analysis. The incubation during 1 or 3 h in presence of the inhibitors of mitochondrial functionality only had a minor effect on motility parameters, decreasing the proportion of the SP1 (fast progressive) subpopulation after 3 h of incubation with ROT, ANTI or OLIGO. The percentage of live spermatozoa with active mitochondria was reduced under the effect of ANTI and CCCP both at 1 and 3 h. In conclusion, mitochondrial function is somehow impaired in frozen thawed bull sperm as not all live cells showed active mitochondria. These results support the findings that bull spermatozoa can alternatively rely on oxidative phosphorylation or glycolysis for energy obtainment and that their mitochondria are less affected by ETC inhibitors.

Post-Thaw Parameters of Buck Semen Quality after Soy Lecithin Extender Supplementation with Fumaric Acid

The supplementation of cryopreservation media with antioxidants improves the post-thaw quality and fertilizing ability of spermatozoa. To maximize the fertility of frozen-thawed buck spermatozoa, further research is required to overcome obstacles that have yielded controversial results and standardize protocols. In the present work, the effect of adding fumaric acid (a well-described antioxidant) to a soy lecithin semen extender on certain quality parameters of spermatozoa following freezing and thawing was examined for the first time. Five sexually mature Skopelos bucks were used, and ejaculates were collected with an artificial vagina. The semen samples (98 samples, five replicates) were diluted (400 × 106 spermatozoa/mL) with OviXcell®, supplemented with fumaric acid (0 mM, 2.15 mM, 10 mM or 30 mM), equilibrated (5 °C; 3 h), packed (0.5 mL straws), frozen and stored (-196 °C) until further processing. After thawing, the spermatozoa total and progressive motility (CASA), viability (eosin-nigrosin), membrane functional integrity (HOST), acrosome integrity (SpermBlue®) and mitochondrial function (Rhodamine-123/SYBR-14/PI) were evaluated. Statistical analysis was performed with one-way ANOVA, followed by Duncan's test; significance was set at 0.05. The addition of 2.15 mM fumaric acid improved (p < 0.05) spermatozoa viability, membrane functional integrity, acrosome integrity and mitochondrial function compared to all other concentrations. The addition of 30 mM fumaric acid decreased (p < 0.05) spermatozoa viability and mitochondrial function compared to all other concentrations. These results indicate a beneficial effect of a 2.15 mM fumaric acid addition to a soy lecithin extender on post-thaw buck spermatozoa quality. Further research is required to evaluate the in vivo fertility of frozen-thawed buck spermatozoa treated with fumaric acid, as well as to elucidate the mechanism of action of fumaric acid in spermatozoa.

Plasma membrane lipid composition and metabolomics analysis of Yorkshire boar sperms with high and low resistance to cryopreservation

The resistance of sperm to freezing varies widely among boars. The semen ejaculate of different boars can be grouped into poor freezability ejaculate (PFE) and good freezability ejaculate (GFE). In this study, five Yorkshire boars each of the GFE and PFE were selected by comparing the changes in sperm motility before and after cryopreservation. Firstly, we found that the sperm plasma membrane of the PFE group showed weak integrity after PI and 6-CFDA staining. Then the electron microscopy results verified that the plasma membrane condition of all segments of GFE was better than that of PFE segments. Furthermore, the lipid composition of sperm plasma membranes in GPE and PFE sperm was analyzed by using mass spectrometry, and 15 lipids showed differences between the two groups. Among those lipids, only phosphatidylcholine (PC) (14:0/20:4) and phosphatidylethanolamine (PE) (14:0/20:4) were higher in PFE. The remaining lipid contents, including those of dihydroceramide (18:0/18:0), four hexosylceramides (18:1/20:1, 18:0/22:1, 18:1/16:0, 18:1/18:0), lactosylceramide (18:1/16:0), two hemolyzed phosphatidylethanolamines (18:2, 20:2), five phosphatidylcholines (16:1/18:2, 18:2/16:1, 14:0/20:4, 16:0/18:3, 18:1/20:2), and two phosphatidylethanolamines (14:0/20:4, 18:1/18:3), were all positively correlated with resistance to cryopreservation (p < 0.05, r > 0.6). Moreover, we analyzed the metabolic profile of sperm using untarget metabolomic. KEGG annotation analysis revealed that the altered metabolites were mainly involved in fatty acid biosynthesis. Finally, we determined that the contents of oleic acid, oleamideetc, N8-acetylspermidine etc., were different between GFE and PFE sperm. In summary, the different lipid metabolism levels and long-chain polyunsaturated fatty acids (PUFAs) in plasma membrane may be key factors contributing to differences in sperm resistance to cryopreservation among boars.

Antioxidant additive melatonin in tris-based egg yolk extender improves post-thaw sperm attributes in Hariana bull

In the study, melatonin, a known antioxidant pineal peptide was used as an additive in the tris-egg yolk glycerol-based semen extender in Hariana bull semen and post-thaw sperm characters were evaluated. In the study, Group I was a control without melatonin; and Group II, III, and IV were having 0.5 mM, 1 mM, and 2 mM melatonin/80 × 10⁶ spermatozoa, respectively were treatment groups. Thirty-two semen ejaculates from 4 Hariana bulls were processed for freezing and post-thaw sperm characteristics were evaluated. Sperm motility, velocity, the viability with intact membrane, and total antioxidant capacity were markedly (P < 0.05) improved in Group IV compared to all other groups. The lipid peroxidation and total protein carbonylation were substantially (P < 0.05) decreased in Group IV compared to all other groups. The population of cryocapacitated, acrosome-reacted, and apoptotic-like spermatozoa were significantly (P < 0.05) decreased in Group IV. Further, the relative band intensity of 74 kDa protein and percent of spermatozoa showing positive immune reactivity to tyrosine-phosphorylated proteins was decreased in Group IV. The progesterone-receptor ligand binding, in vitro capacitation response, and Vanguard distance were markedly (P < 0.05) improved in Group IV. In summary- Group IV having 2 mM melatonin was found to be optimal in providing cryoprotective effects to Hariana bull spermatozoa after freezing-thawing and can be suitably used as a semen additive during semen cryopreservation.

Assisted reproductive technologies (ARTs) in Mithun (Bos frontalis): What progress has been made so far? An overview

Mithun, a unique bovine species, endemic to parts of North East India and plays an important role in the socioeconomic, cultural and religious fabrics of the local tribal population. To date, Mithuns are reared in a traditional free-range system by communities and increased deforestation, agricultural commercialization, disease outbreaks and indiscriminate slaughtering of elite Mithun for table purposes have significantly decreased its habitat and the elite Mithun population. Greater genetic gain is achieved with the implementation and effective use of assisted reproductive technologies (ARTs); however, presently it is limited to organized Mithun farms. At a slow pace, Mithun farmers are adopting semi-intensive rearing systems and interest in the use of ARTs is gradually escalating in Mithun husbandry. This article reviews the current status of ARTs such as semen collection and cryopreservation, estrus synchronization and timed artificial insemination (TAI), multiple ovulation and embryo transfer and in vitro embryo production and future perspectives in Mithun. Mithun semen collection and cryopreservation have been standardized, and estrus synchronization and TAI are suitable technologies that can be easily implemented under field conditions in near future. The establishment of an open nucleus-breeding system under community participatory mode along with the introduction of the ARTs is an alternative to the traditional breeding system for rapid genetic improvement of Mithun. Finally, the review considers the potential benefits of ARTs in Mithun and future research should include the use of these ARTs which will provide additional opportunities for improved breeding regimens in Mithun.

Effect of Magnetized Freezing Extender on Membrane Damages, Motility, and Fertility of Boar Sperm Following Cryopreservation

Magnetized water is defined as the amount of water that has passed through a magnet. The magnetic field weakens the hydrogen bonds between the water molecules, leading to the magnetized liquid acquiring special characteristics such as easy supercooling and forming smaller ice crystals. We researched the influences of a magnetized freezing extender on cell membrane damage and in vitro fertilization of boar sperm during cryopreservation. The freezing extenders were passed through 0, 2000, 4000, and 6000 gausses (G) of magnetic devices using a liquid cycling pump system and then used for the sperm freezing process. The damage to plasma, acrosomal, and mitochondrial membranes in frozen-thawed spermatozoa was investigated by flow cytometry, and motility was assessed using the CASA system. The fertility of frozen-thawed sperm was estimated using in vitro fertilization. The damage to the membranes was significantly decreased in the magnetized freezing extender by the 6000 G magnetic field compared to that of the control in frozen-thawed sperm, and motility was increased in the 6000 G group. Although there were no significant differences in the cleavage rates of in vitro fertilized oocytes among the treatment groups, the ratio of blastocyst formation increased in the magnetized freezing extender groups compared with that in the control group. The number of blastocysts was significantly higher in the 4000 G group than in the 0 G group. In conclusion, these results suggest that a magnetized freezing extender could improve the freezability of sperm and the development of oocytes fertilized in vitro with frozen-thawed sperm.

Quercetin: Putative effects on the function of cryopreserved sperms in domestic animals

Quercetin is one of the most used antioxidant flavonoids and largely exists in many fruits and vegetables because of its capability to scavenge the free reactive oxygen species (ROSs) by repressing lipid peroxy radical fusion, metal ion chelating through enzyme inhibition, and adopting the repair mechanisms. It also exhibits various biological actions, including antioxidative, anti-inflammatory and antimicrobial activities. Furthermore, it contributes well to sustaining the endogenous cellular antioxidant defence system. The process of cryopreservation is associated with increased oxidative stress, and some steps are potential sources of ROSs, including the method of semen collection, handling, cryopreservation culture media, and thawing, which result in impaired sperm function. Several antioxidants have been proposed to counteract the harmful impact of ROS during semen cryopreservation. The antioxidant capability of quercetin has been verified in different animal species for providing valuable defence to sperm during the cryopreservation process. The beneficial properties of quercetin on various parameters of fresh and post-thaw sperm in different species are clarified in this review. More in-depth investigations are required to clarify quercetin's mechanism of action in different animal species.

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.

Effects of cryopreservation on the mitochondrial bioenergetics of bovine sperm

This study evaluated the bioenergetic map of mitochondria metabolism in cryopreserved bovine sperm. The detected oligomycin-sensitive basal respiration supported ATP production; frozen-thawed spermatozoa were found to have a coupling efficiency higher than 0.80. Cell respiration, however, was not stimulated by the protonophoric action of FCCP, as its titration with 1, 2, 4 and 6 μM did not stimulate the uncoupling activity on oxidative phosphorylation as highlighted by unresponsive oxygen consumption. The unusual effect on the stimulation of maximal respiration was not related to fibronectin- or PDL-coated plates used for cellular metabolism analysis. Conversely, irradiation of frozen-thawed bovine sperm with the red light improved mitochondrial parameters. In effect, the maximal respiration of red-light-stimulated sperm in PDL-coated plates was higher than the non-irradiated. In spite of this, red-light irradiation had no impact on membrane integrity and mitochondrial activity evaluated by epifluorescence microscopy.

Effect of platelet-rich plasma (PRP) on post-thaw quality, kinematics and in vivo fertility of fertile and subfertile buffalo (Bubalus bubalis) spermatozoa

This study investigated the effect of adding platelet-rich plasma (PRP) in semen extender prior cryopreservation on post-thaw quality, kinematics, and in vivo fertility of fertile and subfertile buffalo spermatozoa. Eleven buffalo bulls were classified based on their conception rate (CR) into fertile (n = 8, CR > 55%) and subfertile (n = 3, CR < 35%) groups. Ejaculates were collected with artificial vagina, pooled, and dispensed into 6 aliquots, diluted with Tris-egg yolk-glycerol extender supplemented with different proportions of PRP [0% (control), 5%, 10%, 15%, 20%, and 25%] followed by cryopreservation using standard procedures. Post-thaw sperm quality, kinematics, antioxidant activity, cryosurvival rate, and in vivo fertility were compared between fertile and subfertile groups and among proportions of PRP within each group. The results showed that 15% PRP greatly (P < 0.001) improved sperm characteristics, average path velocity, and curvilinear velocity of the subfertile group. Interestingly, 5%, 10%, and 15% PRP greatly (P < 0.001) reduced malondialdehyde content and improved enzymatic (glutathione peroxidase and superoxide dismutase) and total antioxidant capacity in fertile and subfertile groups. However, these three proportions of PRP significantly (P < 0.001) improved the cryosurvival rate of the subfertile group; only 15% PRP greatly improved CR of subfertile (60.83% vs. 34.17%) animals to be comparable with that of fertile ones treated with 5 (59.17%) and 10% (60.83%) PRP. In conclusion, adding 15% PRP to semen extender before cryopreservation is recommended to improve post-thaw quality, antioxidant activity, and in vivo fertility of buffalo semen particularly of the subfertile animals.

Glutathione and selenium nanoparticles have a synergistic protective effect during cryopreservation of bull semen

Introduction

In the present study, the synergistic protective effect of co-supplementation of glutathione (GSH) with selenium nanoparticles (SeNPs) on the cryopreservation efficiency of bull semen was analyzed.

Methods

After collection, the ejaculates of Holstein bulls were subsequently diluted with a Tris extender buffer supplemented with different concentrations of SeNPs (0, 1, 2, and 4 μg/ml), followed by semen equilibration at 4°C and assessment of sperm viability and motility. Subsequently, the ejaculates of Holstein bulls were pooled, split into four equal groups, and diluted with a Tris extender buffer supplemented with basic extender (negative control group, NC group), 2 μg/ml SeNPs (SeNPs group), 4 mM GSH (GSH group), and 4 mM GSH plus 2 μg/ml SeNPs (GSH + SeNPs group). After cryopreservation, motility, viability, mitochondrial activity, plasma membrane integrity, acrosome integrity, concentration of malondialdehyde (MDA), superoxide dismutase (SOD), and catalase (CAT), and ability of frozen-thawed sperm cells to support in vitro embryonic development were evaluated.

Results and discussion

No side effect of SeNPs concentrations applied in the current study on the motility and viability of equilibrated bull spermatozoa was found. Meanwhile, supplementation of SeNPs significantly promoted the motility and viability of equilibrated bull spermatozoa. Furthermore, the co-supplementation of GSH with SeNPs effectively protected bull spermatozoa from cryoinjury as expressed by promoting semen motility, viability, mitochondrial activity, plasma membrane integrity, and acrosome integrity. Finally, the enhanced antioxidant capacity and embryonic development potential in the frozen-thawed bull spermatozoa cryopreserved by co-supplementation of GSH with SeNPs further confirmed the synergistic protective effect of co-supplementation of GSH with SeNPs on the cryopreservation of bull semen.

Evaluation of lipidomic change in goat sperm after cryopreservation

The current study aimed to detect the relationship between the spermatozoa cryotolerance and the post-thawed sperm lipidome. Ejaculates from 20 goats, and performed a uniform frozen-thawed procedure in this study. According to the total motility of thawed sperm of goats, semen samples were classified into HF group (High Freezers, n = 8) with >60% total motility and LF group (Low Freezers, n = 8) with < 45% total motility. The lipidomic analysis based on UHPLC-MS/MS was utilized to investigate the relationship between sperm cryotolerance and their lipid metabolites expression. The results showed that the cryotolerance of sperm from different individual goats were in great variation. The total motility of post-thawed sperm in HF group (60.93 ± 2.43%) is significantly higher than that in LF group (34.04 ± 3.41%, P < 0.01). And the post-thawed sperm in HF group exhibited significantly higher plasma membrane (59.06 ± 2.34%) and acrosome integrity (62.93 ± 1.15%) than that in LF group (34.06 ± 4.85%, 44.92 ± 2.19% respectively, P < 0.01). The total of 29 lipid subclasses and 1,133 lipid molecules in the post-thawed goat sperm were identified by lipidomics analysis. The lipid content of thawed sperm in HF group was higher than that in LF group, the lipid profile in HF group was significantly separated from LF group, which indicated that the difference in lipid composition and lipid metabolism mode of sperm between the two groups was existed, especially the expression of phosphatidylcholine and triglyceride molecules. In conclusion, the cryotolerance of sperm from different individual goats were in great variation. Sperm with high cryotolerance may be able to uptake more lipids during cryopreservation. The increase in phosphatidylcholine and triglyceride content of thawed. Sperm may relate to more active lipid anabolic processes.

Contributions of seminal plasma proteins to fertilizing ability of bull sperm: A meta-analytical review

Seminal plasma is a dynamic, intricate combination of fluids from the testicles, epididymides, seminal vesicles, bulbourethral glands, and prostate, containing molecules that modulate sperm functions, post-fertilization events, and the female reproductive tract physiology. Significant variations in sperm parameters and fertility status of bulls relate to differences in the seminal plasma proteome. In this framework, a meta-analytical study was conducted examining 29 studies (published between 1990 and 2021) to ascertain the effects of seminal fluid proteins on parameters associated with bull fertility and the influence of distinct methodologies on such effects. Our results revealed that seminal proteins ameliorate sperm parameters, such as motility, integrity, capacitation, and fertilizing ability, and favours sperm protection. Seminal binder of sperm proteins and beta-defensin 126 highly favoured sperm protection when cells were collected from the epididymis by retrograde flux and analysed under room temperature conditions. Furthermore, seminal proteins improved the motility and quality of Bos taurus sperm collected by artificial vagina, mainly in the presence of heparin-binding proteins. The key limitations faced by this meta-analysis were the paucity of studies evaluating the effects of whole seminal fluid proteins and the limited number of studies conducted in vivo. In conclusion, the present meta-analytical study confirms that seminal proteins improve fertility-related parameters in the bovine species. However, methodological strategies used by authors are diverse, with distinct endpoints and methods. Thus, the translational aspects of seminal plasma research should be taken into consideration to precisely define how seminal proteins can be harnessed to advance reproductive biotechnology.