Changes in sperm quality and lipid composition during cryopreservation of boar semen

Fatty acid composition and biophysical characteristics of the cell membrane of feline spermatozoa

Sperm membrane composition and biophysical characteristics play a pivotal role in many physiological processes (i.e. sperm motility, capacitation, acrosome reaction and fusion with the oocyte) as well as in semen processing (e.g. cryopreservation). The aim of this study was to characterize the fatty acid content and biophysical characteristics (anisotropy, generalized polarization) of the cell membrane of domestic cat spermatozoa. Semen was collected from 34 adult male cats by urethral catheterization. After a basic semen evaluation, the fatty acid content of some of the samples (n = 11) was evaluated by gas chromatography. Samples from other individuals (n = 23) were subjected to biophysical analysis: membrane anisotropy (which is inversely proportional to membrane fluidity) and generalized polarization (describing lipid order); both measured by fluorimetry at three temperature points: 38 °C, 25 °C and 5 °C. Spermatozoa from some samples (n = 10) were cryopreserved in TRIS egg yolk-glycerol extender and underwent the same biophysical analysis after thawing. Most fatty acids in feline spermatozoa were saturated (69.76 ± 24.45%), whereas the polyunsaturated fatty acid (PUFA) content was relatively low (6.12 ± 5.80%). Lowering the temperature caused a significant decrease in membrane fluidity and an increase in generalized polarization in fresh spermatozoa, and these effects were even more pronounced following cryopreservation. Anisotropy at 38 °C in fresh samples showed strong positive correlations with viability and motility parameters after thawing. In summary, feline spermatozoa are characterized by a very low PUFA content and a low ratio of unsaturated:saturated fatty acids, which may contribute to low oxidative stress. Cryopreservation alters the structure of the sperm membrane, increasing the fluidity of the hydrophobic portion of the bilayer and the lipid order in the hydrophilic portion. Because lower membrane fluidity in fresh semen was linked with better viability and motility after cryopreservation, this parameter may be considered an important factor in determination of sperm cryoresistance.

Proteomic Analysis of Frozen-Thawed Spermatozoa with Different Levels of Freezability in Dairy Goats

The results of artificial insemination (AI) are adversely affected by changes in sperm motility and function throughout the cryopreservation procedure. The proteome alterations of frozen-thawed spermatozoa with various levels of freezability in dairy goats, however, remain largely unknown. To discover differentially expressed proteins (DEPs) and their roles in dairy goat sperm with high or low freezability (HF or LF), we conducted 4D-DIA quantitative proteomics analysis, the results of which are presented in this work. Additionally, we explored the underlying processes that may lead to the variations in sperm freezing resistance. A total of 263 DEPs (Fold Change > 2.0, p-value < 0.05) were identified between the HF group and LF group in frozen-thawed dairy goat spermatozoa. In our Gene Ontology (GO) enrichment analysis, the DEPs were mostly associated with the regulation of biological processes, metabolic processes, and responses to stress and cellular component biogenesis. Our Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis also revealed that the DEPs were predominantly engaged in oxidative phosphorylation, N-Glycan biosythesis, and cysteine and methionien metabolism. A protein-protein interaction (PPI) network analysis revealed 14 potential proteins (NUDFB8, SDHC, PDIA4, HSPB1, etc.) that might influence the freezability of dairy goat sperm. These findings shed light on the processes underlying alterations in the proteome and sperm freezability, aiding further research on sperm cryopreservation.

The Role of Melatonin to Ameliorate Oxidative Stress in Sperm Cells

It is widely accepted that oxidative stress (OS) coming from a wide variety of causes has detrimental effects on male fertility. Antioxidants could have a significant role in the treatment of male infertility, and the current systematic review on the role of melatonin to ameliorate OS clearly shows that improvement of semen parameters follows melatonin supplementation. Although melatonin has considerable promise, further studies are needed to clarify its ability to preserve or restore semen quality under stress conditions in varied species. The present review examines the actions of melatonin via receptor subtypes and its function in the context of OS across male vertebrates.

Palm Kernel Meal Protein Hydrolysates Enhance Post-Thawed Boar Sperm Quality

Boar sperm is sensitive to particular conditions during cryopreservation, resulting in an extreme reduction in fertilizing ability due to damage to the sperm membranes. PKMPH contains bioactive peptides that have antioxidant and antimicrobial activities. There is no information on the use of palm-kernel-meal-derived bioactive peptides for boar semen cryopreservation. This study aimed to examine the effects of bioactive peptides from PKMPH on post-thawed boar sperm quality. Boar semen ejaculates (n = 17) were collected and divided into six equal aliquots based on PKMPH concentrations (0, 1.25, 2.5, 5, 10, and 15 µg/mL) in a freezing extender. Semen samples were processed and cryopreserved using the liquid nitrogen vapor method. Thereafter, the frozen semen samples were thawed at 50 °C for 12 s and evaluated for sperm motility using a computer-assisted sperm analyzer and for sperm viability, acrosome integrity, mitochondrial function, and lipid peroxidation by measuring the level of malondialdehyde (MDA). The results demonstrate that the supplementation of PKMPH with 2.5 µg/mL afforded superior post-thawed sperm qualities, such as increased total motility, viability, acrosome integrity, and mitochondrial function by 10.7%, 12.3%, 18.3%, and 12.7%, respectively, when compared to the control group. PKMPH at a concentration of 2.5 µg/mL showed the lowest level of MDA (40.6 ± 2.0 µMol/L) compared to the other groups. In conclusion, adding PKMPH peptides at 2.5 µg/mL to the freezing extender reduced the oxidative damage associated with cryopreservation and resulted in higher post-thawed sperm quality.

Correlation between fatty acids levels in chicken, duck, goose, pigeon, quail and turkey egg yolks and post-thawed quality of ram semen

The comparison between adding egg yolks (EY) of chicken, duck, goose, pigeon, Japanese quail or turkey to the Tris glycerol extender on the quality of ram semen before freezing and post-thawing was evaluated. The correlation between fatty acids levels in egg yolks of different avian species and the post-thawed quality of ram semen was studied. The pooled ejaculates collected from five rams were extended with Tris EY glycerol extenders containing the EY of chicken, duck, goose, pigeon, quail or turkey and cryopreserved at -196°C. The straws were evaluated before freezing and post-thawing for sperm motility using a sperm cell analyser, vitality using a FluoVit kit and abnormality using a SpermBlue stain besides plasma-membrane and DNA integrities using a hypo-osmotic swelling test and a Halomax kit, respectively. The moisture, ash, protein and fatty acid (FA) contents of EY of chicken, duck, goose, pigeon, quail and turkey were analysed using a gas chromatograph. The chicken and quail EY extenders significantly improved the total progressive motility (32.05 ± 1.41 and 31.68 ± 1.43, respectively), vitality, plasma membrane and DNA integrities and abnormalities of post-thawing ram semen in comparison with other EY extenders. Pigeon EY had the lowest saturated fatty acids (SFAs) in comparison with the other types of EYs. The chicken and turkey EYs had the lowest percentage of (monounsaturated fatty acids) MUFAs in comparison with the other types of EYs. The highest percentage of polyunsaturated fatty acids (PUFAs) was observed in the turkey, pigeon and chicken EYs which were considered double or triple their percentage in duck and goose EYs, respectively. Significant positive correlations existed between SFAs levels and total motility, vitality, plasma membrane functionality and DNA integrity (0.77, 0.80, 0.67, 0.52, respectively). Significant negative correlations existed between gondoic EY levels and total motility, vitality, plasma membrane functionality and DNA integrity. In conclusion, the EYs of duck, goose, pigeon or turkey cannot substitute the chicken EY in ram semen extenders as they gave lower post-thawing quality. The quail EY can be used as a good replacer for chicken EY in the extender used for cryopreservation of ram semen. The EY composition of FAs can significantly affect the quality of ram semen post-thawing.

Genome-wide association and genomic prediction for a reproductive index summarizing fertility outcomes in U.S. Holsteins

Subfertility represents one major challenge to enhancing dairy production and efficiency. Herein, we use a reproductive index (RI) expressing the predicted probability of pregnancy following artificial insemination (AI) with Illumina 778K genotypes to perform single and multi-locus genome-wide association analyses (GWAA) on 2,448 geographically diverse U.S. Holstein cows and produce genomic heritability estimates. Moreover, we use genomic best linear unbiased prediction (GBLUP) to investigate the potential utility of the RI by performing genomic predictions with cross validation. Notably, genomic heritability estimates for the U.S. Holstein RI were moderate (h2 = 0.1654 ± 0.0317-0.2550 ± 0.0348), while single and multi-locus GWAA revealed overlapping quantitative trait loci (QTL) on BTA6 and BTA29, including the known QTL for the daughter pregnancy rate (DPR) and cow conception rate (CCR). Multi-locus GWAA revealed seven additional QTL, including one on BTA7 (60 Mb) which is adjacent to a known heifer conception rate (HCR) QTL (59 Mb). Positional candidate genes for the detected QTL included male and female fertility loci (i.e. spermatogenesis and oogenesis), meiotic and mitotic regulators, and genes associated with immune response, milk yield, enhanced pregnancy rates, and the reproductive longevity pathway. Based on the proportion of the phenotypic variance explained (PVE), all detected QTL (n = 13; P ≤ 5e - 05) were estimated to have moderate (1.0% < PVE ≤ 2.0%) or small effects (PVE ≤ 1.0%) on the predicted probability of pregnancy. Genomic prediction using GBLUP with cross validation (k = 3) produced mean predictive abilities (0.1692-0.2301) and mean genomic prediction accuracies (0.4119-0.4557) that were similar to bovine health and production traits previously investigated.

Comparative iTRAQ proteomics identified proteins in fresh and frozen thawed yak spermatozoa

The changes in semen and cryodamage after the cryopreservation process negatively affect sperm function and motility. However, possible proteomic alterations of yak semen during cryopreservation have not yet been achieved. In this study, we compared proteomes of fresh and frozen thawed yak sperm using iTRAQ combined with LC-MS/MS proteome approach. Totally, 2064 proteins were quantitatively identified, including 161 in fresh sperm that showed significant differences compared to frozen thawed sperm. According to the Gene ontology (GO) enrichment analysis, differentially expressed proteins (DEPs) are predominantly associated with spermatogenesis, tricarboxylic acid cycle, ATP synthesis, and differentiation biological process. Furthermore, the Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis showed that DEPs were mainly involved in metabolic pathways related to pyruvate metabolism, carbon metabolism, glycolysis/gluconeogenesis, together with the citrate (TCA) cycle. In the analysis of the protein-protein interaction (PPI) network, 15 potential proteins (PDHB, DLAT, PDHA2, PGK1, TP5C1, etc.) that could be related to the sperm quality of the yaks were obtained. Furthermore, 6 DEPs were validated by parallel reaction monitoring (PRM), confirming that the iTRAQ data were reliable. These results indicate that cryopreservation alters the proteome of yak sperm, which is possibly related to cryodamage and fertilization ability.

Cryoprotectant effects of natural honey on spermatozoa quality of pre-freezing and frozen-thawed boar semen

Natural honey has been successfully used in the preservation of mammalian gametes because of its beneficial properties. The objectives of this study were to determine the inclusion level of honey in extender for improving boar semen quality before freezing and to investigate the effects of honey inclusion in extender and freezing media on post-thaw quality of frozen-thawed boar semen samples. Ejaculates from six terminally crossbred boars were collected using the gloved-hand technique for two experiments. Experiment 1 was a randomized block design, evaluating four inclusion levels of honey in boar semen extender [Control (0H)-Androhep Plus or Androhep Plus with 0.25%, 0.50%, and 0.75% honey (0.25H, 0.50H, and 0.75H respectively)]. Ejaculates were pooled, aliquoted according to treatments, and cooled for 24 h at 17 ºC. The results of this experiment were used to determine inclusion levels in exp. 2. Experiment 2 was a 2 x ×3 factorial design, evaluating the inclusion of honey in boar semen extender and freezing media. Semen samples from individual boars were cooled in extender with or without honey (C0: Androhep Plus; C1: Androhep Plus + 0.25% honey). After 24 h, semen samples were evaluated, diluted in lactose-egg yolk (LEY) media, and one of three freezing media types; F0: 93% LEY + 6% glycerol + 1% Equex-STM Paste (ESP); F1: 93% LEY + (3% glycerol and 3% honey) + 1% ESP; and F2: 93% LEY + 6% glycerol + (0.5% ESP and 0.5% honey). Samples were frozen in 0.5 mL straws using a controlled-rate freezer and stored in liquid nitrogen. In exp. 1, 0.25H and 0.50H improved motility (P = 0.033) and progressive motility (P = 0.001) of cooled boar semen. Nevertheless, 0.25H was selected for exp. 2. In exp. 2, post-thaw motility and progressive motility were highest (P < 0.05) in C0F2 but not different from C1F2. Morphologically normal cells and acrosomes were higher with all inclusion levels of honey (P < 0.05). In conclusion, 0.25% and 0.50% inclusion of honey in Androhep Plus improves motility and progressive motility of cooled boar semen samples after 24 h. Supplementing Androhep Plus with 0.25% honey maintains higher normal sperm cells and acrosomes of cryopreserved boar semen. Replacing 50% Equex-STM paste with honey in freezing media improves post-thaw sperm motility, progressive motility, percentage of normal sperm, and acrosome of cryopreserved boar semen.

Linseed oil in boar's diet improved in vivo fertility and antioxidant status

The reactive oxygen species (ROS) which are produced during storage of boar semen are causing oxidative stress and leads to poor fertility. Also, tropical and sub-tropical weather condition adversely impacts the physicomorphological quality and fertility of boar sperm. The aim of this study was to examine the effects of feeding linseed oil to boar on its seminal attributes, sperm kinetics, biomarkers of antioxidant, fatty acid profile of seminal plasma (SP) and sperm and in vivo fertility. Six Hampshire crossbreed boars were fed with 90 ml linseed oil (LIN) whereas six Hampshire crossbreed boars were fed 90 ml canola oil (CON) for 16 weeks. Sperm quality was evaluated (60 ejaculates for each group; a total of 120 ejaculates) for motility, livability, abnormal morphology, acrosomal membrane integrity, hypo-osmotic swelling test (HOST) and sperm kinetic parameters by computer assisted semen analysis (CASA) at 0 h and at 72 h of storage at 17°C. Biomarkers of antioxidant (glutathione peroxidase; GPx, catalase; CAT, total antioxidant capacity; TAC) and malondialdehyde (MDA) were measured in SP and serum. Gas chromatography-mass spectrometry (GC-MS) was used for the estimation of fatty acid composition of SP and sperm. Boars fed with linseed oil had higher semen volume (p < .01) and more total sperm numbers (p < .01). Feeding linseed oil to boar enhanced seminal attributes (p < .05) at 0 h as well as at 72 h of storage. Linseed oil feeding (p < .01) improved biomarkers of antioxidants and significantly (p < .01) lowered the lipid peroxidation in serum and SP. Linseed oil feeding (p < .05) increased the proportion of alpha linolenic (ALA), arachidonic and docosahexaenoic (DHA) fatty acids in SP. The ratio of n-6 to n-3 fatty acids in sperm increased significantly (p < .01) in treatment group. Farrowing rate was significantly (p < .05) higher in treatment group. In conclusion, feeding linseed oil to boar improved the in vivo fertility, enhanced antioxidant capacity and increased the DHA content of SP and sperm.

"Fine feathers make fine birds" - The mammalian sperm plasma membrane lipid composition and effects on assisted reproduction

The sperm plasma membrane is important in modulating many sperm functions. The sperm membrane is composed of a complex mixture of lipids including phospholipids, glycolipids and sterols. There are differences of sperm membrane composition among mammalian species with two groups differing in the most abundant polyunsaturated fatty acid (PUFA), either docosahexaenoic (ω-3 PUFA) or docosapentaenoic acid (ω-6 PUFA). During testicular and epididymal maturation, composition of the sperm plasma membrane evolves with spermatozoa gaining the capacity for fertilization. The importance of fatty acid metabolism for complete spermatogenesis has been elucidated using gene knockout mice. During epididymal transit cholesterol content decreases and PUFA content increases, conferring more fluidity properties to the sperm membrane. The relatively lesser content of antioxidant enzymes and the relatively larger content of PUFA make the spermatozoa particularly susceptible to lipid peroxidation during sperm preservation. In numerous studies, there was adding of PUFA and antioxidants to the diet of animals or to semen extenders with the aim to improve sperm membrane integrity. This review highlights the current knowledge on the sperm membrane composition and effects on sperm function in mammalian domestic animals.

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.

Influence of alpha linolenic acid on the motility, viability, antioxidant activity and fertility of frozen-thawed New Zealand white rabbit buck semen

Freezing and thawing processes result in production and accumulation of high concentrations of reactive oxygen species that are detrimental to spermatozoal motility and fertility. Therefore, supplementation of exogenous source of antioxidants to freezing diluent is crucial. The aim of the present study was to investigate for the first time whether supplementation of semen diluent with alpha linolenic acid (ALA) can improve motility, viability, membrane integrity, antioxidant status and fertility of post-thaw rabbit spermatozoa. Semen was collected and pooled from fifteen New Zealand white rabbit bucks. Semen samples were diluted with a tris-citrate-glucose (TCG) extender supplemented with ALA (0, 50, 75 and 100 μmol). Then, extended rabbit semen was cooled at 5°C and cryopreserved in liquid nitrogen. After thawing, spermatozoal quality parameters (individual motility %, viability %, osmotic resistance %, and acrosome integrity %), antioxidant activity (SOD, CAT, and GSH activities), lipid peroxidation (malondialdehyde) and fertility (conception and kindling rates) were evaluated. Results revealed that supplementation of rabbit semen extender with 50 μmol ALA significantly (P<0.05) increased spermatozoal characteristics including motility (56.54%), viability (60.01%), acrosome status (72.66%) and membrane integrity (59.13%). The activity of semen antioxidant enzymes (SOD, CAT, and GSH) showed a significant improvement with a marked decrease in lipid peroxidation. Moreover, the conception (73.30%) and kindling (70.00%) rates were significantly (P<0.05) higher in does inseminated with thawed semen treated with 50 μmol ALA in comparison with other concentrations (0, 75 and 100 μmol). In summary, supplementation of rabbit semen extender with 50 μmol ALA improved motility, viability, membrane integrity, acrosome integrity, antioxidant enzymes activity and fertility of post-thaw rabbit spermatozoa. Our findings suggested that higher concentrations of ALA are detrimental to post-thaw characteristics of New Zealand white rabbit buck spermatozoa. To achieve better results, the semen freezing extender should be supplemented with ALA at lower concentrations, especially 50 μmol.

Linseed oil in boar's diet during high temperature humidity index (THI) period improves sperm quality characteristics, antioxidant status and fatty acid composition of sperm under hot humid sub-tropical climate

Environmental heat stress in sub-tropical climates negatively impacts boar semen production and its quality. The present study aimed to examine the heat stress alleviating effects of dietary linseed oil on semen quality and antioxidant status of boar, in the summer and winter seasons in sub-tropical climate. Six Hampshire crossbreed boars were fed with 90 mL linseed oil (treatment) whereas six boars of the same breed were fed 90 mL vegetable oil (control) for sixteen weeks during both season. Sperm quality was assessed for motility, viability, abnormality, acrosomal integrity, and Hypo-osmotic swelling test (HOST). Sperm velocity attributes were assessed by computer-assisted semen analysis (CASA). Antioxidants (glutathione peroxidase; GPx, catalase; CAT, total antioxidant capacity; TAC and nitric oxide; NO) and lipid peroxidation (malondialdehyde; MDA) were measured in seminal plasma and serum. Gas chromatography-mass spectrometry (GC-MS) was used for the estimation of fatty acid composition of seminal plasma and spermatozoa. Feeding linseed oil to the boars significantly (p < 0.05) improved sperm quality at the fresh stage and after 72 h of liquid storage in both season. There was a significant (p < 0.01) effect of treatment and season on semen quality parameters. Significant boar (p < 0.05) effect was recorded on reaction time, semen volume, sperm abnormality, acrosomal integrity and HOST reactive sperm. There was a significant (p < 0.01) effect of treatment and season on the velocity attributes viz. VAP, VSL, VCL, ALH, BCF and STR%. Linseed oil supplementation significantly (p < 0.01) enhanced antioxidant and lowered MDA levels in serum as well as seminal plasma. The concentration of alpha-linolenic (ALA), arachidonic and docosahexaenoic (DHA) fatty acids were significantly (p < 0.01) increased in seminal plasma and sperm after linseed oil supplementation. In conclusion, linseed oil supplementation to boar during high THI months improved the semen quality parameters viz. semen volume, sperm concentration, and progressive motile sperm, along with enhanced antioxidant capacity.

The Protective Role of Melatonin in Sperm Cryopreservation of Farm Animals and Human: Lessons for Male Fish Cryopreservation

Simple Summary

In recent years, cryopreservation of fish sperm has been a rapidly evolving technique that contributes both to the improvement of genetic reproduction programs and the proper management of broodstock as well as to ensuring the viability of endangered species. However, this technique can cause significant damage to sperm, making the use of cryoprotectants and antioxidants in cryopreservation solutions imperative. The hormone melatonin has demonstrated positive effects on the cryopreservation of sperm in both farm animals and humans. Therefore, the plethora of research that has been conducted on animals and humans could be expanded to fish cryopreservation, making melatonin potentially a very promising alternative cryoprotectant.

Abstract

Cryopreservation is a technique that offers various advantages, especially in fish, among others, that makes the reproduction of species easier through a constant supply of sperm, synchronization of the gamete availability of both sexes, storage of semen for genetic improvement programs, reduction in the cost by eliminating the need to maintain male broodstock, and conserving the gametes of endangered species. However, freezing and warming procedures for cryopreservation lead to a reduction in the quality and viability of cryopreserved sperm because of oxidative stress. For this reason, the enrichment of extender media with antioxidants is a common method of cryopreservation of the semen of several fish species. Recently, many studies have been published for the protective role of antioxidants and especially of melatonin on male fertility preservation both in farm animals and humans, demonstrating the beneficial effects of melatonin as a sperm cryoprotectant. On the other hand, very few studies were conducted using melatonin as an antioxidant in different male fish species for semen cryopreservation. We conclude that the use of moderate concentrations of melatonin are beneficial to semen preservation, and the mechanisms through which melatonin acts positively on spermatozoa need to be further investigated to establish improvement protocols for cryopreservation in fish species.

PCR investigation of the vertical transmission of Mycobacterium bovis in Montbéliarde cattle in Gonbad, northeast of Iran

Bovine tuberculosis is an important global zoonosis. The causative agent of the disease is Mycobacterium bovis, belonging to the Mycobacterium tuberculosis complex. This study aimed to identify vertical transmission of Mycobacterium bovis in tuberculin positive pregnant dairy cows referred to the slaughterhouse and commercial sperm used to inseminate them in Gonbad, Gorgan province, Iran, by PCR assay. From March to September 2016, one thousand and seven hundred artificially inseminated cows were subjected to the tuberculin test; then, tuberculin positive cows were referred to the Gonbad slaughterhouse. Samples containing milk, lymph node, placenta, foetal abomasal fluid, and amniotic fluid were prepared from all affected cows and stored at -80 °C until analysis. Bacterial DNA was extracted from all specimens by a commercial kit. Detection was performed by amplifying pncATB gene using special primers via the polymerase chain reaction method. Results of tuberculin test revealed 144 positive cases (8.47%). PCR results for 48 milk samples, 120 biopsy samples, 63 samples of foetuses showed 9, 93 and 43 positive cases, respectively which all belonged to tuberculin positive samples. No positive sperm samples were identified. It was concluded that the infection rate with M. bovis in Montbéliarde cattle was high and also, that vertical transmission was not seen.

Effect of turmeric extract and dimethyl sulfoxide on buffalo semen freezability and fertility

The freeze-thaw process results in structural and functional damages caused by overaccumulation of reactive oxygen species (ROS). Addition of antioxidants to semen extenders is of a great importance to overcome this oxidative damage. The study objective was to evaluate the consequence of using Tris-citric acid fructose egg yolk (TCFY) extender supplemented with a combination of turmeric extract and dimethyl sulfoxide (DMSO) [TTD] on sperm freezability and fertility. From five tubes (each containing 5 mL TCFY), the first tube contained neither turmeric extract nor DMSO and was kept as control. The other four tubes contained 1.5% DMSO plus 100 µL/5 mL, 200 µL/5 mL, 300 µL/5 mL and 400 µL/5 mL turmeric extract. Semen samples were pooled and extended to reach an application of 60×106 sperm/mL (TT1D to TT4D, respectively). Diluted semen was exposed to the freezing protocol. The post cooling results revealed significant improvement in percent of alive spermatozoa in TT1D, significant decrease in sperm abnormalities in all concentrations used, significant improvement in intact acrosome percentage in TT1D, TT2D and TT4D. The post thawing results exhibited significant improvement in sperm motility in TT1D, TT2D and TT4D; significant amelioration of sperm membrane integrity (HOST) in TT1D, TT2D, TT3D and TT4D. Acrosome integrity was maintained in all concentrations as in the control. It was concluded that TT1D revealed the best semen quality in cooled semen; and TT1D, TT2D exhibited the superior post thawing semen quality. In addition, conception rate (CR) of the post-thawed semen was ameliorated in TT1D, TT2D, TT3D and TT4D with TT1D being the best one with this regard.

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.

Use of melatonin in sperm cryopreservation of farm animals: A brief review

Melatonin (MT) is a potent antioxidant with useful applications in several fields. Due to the capacity to scavenge free radicals and enhance cellular endogenous antioxidant defenses, MT is widely used in sperm cryopreservation to protect against oxidative stress-induced damage in frozen-thawed sperm. In this article, there is a review of positive effects of MT supplementation in cryopreservation of sperm from domestic ruminants and swine. There is direct or indirect scavenging of free radicals, preventing lipid peroxidation (LPO), and reducing oxidative stress, therefore, protecting membrane and DNA integrity, enhancing post-thaw antioxidant and enzymatic functions to maintain mitochondrial functions and activity, and regulating ATP production and utilization leading to maintenance of sperm quality, motility, and viability. In addition, MT reportedly inhibits sperm apoptosis, potentially by enhancing sperm viability and modulating abundances of mRNA transcripts.

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.

Swine spermatozoa trigger aggregated neutrophil extracellular traps leading to adverse effects on sperm function

In pigs, the number of PMN in uterus lumen increases within few hours after natural or artificial AI resulting in early PMN-derived innate immune reactions. Sperm-NETs formation was recently reported to occur in various mammalian species. Aim of this study was to investigate direct interactions of boar spermatozoa with swine PMN, the release of sperm-mediated NETs, and to assess NET-derived effects on sperm functionality. Sperm-triggered NETs were visualized by SEM- and immunofluorescence analyses. Sperm-mediated NETosis was confirmed by presence of extruded DNA with global histones and NE. Largest sizes of sperm-mediated aggNETs were detected after 5 h thereby resulting in effective massive sperm entrapment. The number of aggNETs increased from 3 h onwards. Kinetic studies of swine sperm-mediated NETosis showed to be a time-dependent cellular process. In addition, number of NETs-entrapped spermatozoa increased at 3 h of exposure whilst few free spermatozoa were detected after 3 h. Anchored NETs also increased from 3 h onwards. The cytotoxicity of NETs was confirmed by diminution of the total motility and the progressive motility. Spermatozoa membrane integrity and function loss exposed to NETs was confirmed from 3 h. Experiments revealed NETs-derived damaging effects on swine spermatozoa in membrane integrity, motility and functionality. We hypothesize that swine sperm-triggered aggNETs might play a critical role in reduced fertility potential in swine reproductive technique. Thus, aggNETs formation needs to be considered in future studies about uterine environment as well as advance of sperm in the porcine female reproductive tract.

Lipid profile of sperm cells in Thai native and commercial roosters and its impact on cryopreserved semen quality

Plasma membrane lipids are the key factor in the ability of chicken sperm to be frozen. They ensure fluidity and flexibility of the sperm membrane for effective viability and motility during in vitro storage. The objective of this study was to compare the lipid profiles of different native and commercial chicken breeds: native Thai (Pradu Hang Dam) roosters and commercial (Rhode Island Red) roosters, with respect to their frozen sperm quality. In addition, lipid peroxidation and antioxidant enzymes superoxidase dismutase (SOD) and catalase (CAT) were also examined. Semen was collected from 12 roosters of each breed. For fresh semen, parameters assessed include semen volume, pH, sperm concentration, sperm motility, and viability, while for frozen semen, the parameters assessed were sperm motility and viability. Moreover, other parameters assessed included malondialdehyde (MDA) concentration, activities of SOD and CAT, and fatty acid profile. We found that sperm viability and motility of frozen semen were higher in the commercial breed than in the native breed (P < 0.05). The commercial chicken breed had higher MDA concentration than the native breed (P < 0.05), but antioxidant enzymes remained unchanged in both. Levels of arachidonic acid (AA; C20:4n-6) and docosahexaenoic acid (DHA; C22:6n-3) were significantly higher (P < 0.05) in the commercial than in the native breed; however, n-6 to n-3 ratios were not different. In conclusion, our study found that lipid profiles have an influence on frozen sperm viability and motility between the breeds. Polyunsaturated fatty acids, particularly AA and DHA, are beneficial to sperm quality.

Advancing Semen Evaluation Using Lipidomics

Developing a deeper understanding of biological components of sperm is essential to improving cryopreservation techniques and reproductive technologies. To fully ascertain the functional determinants of fertility, lipidomic methods have come to the forefront. Lipidomics is the study of the lipid profile (lipidome) within a cell, tissue, or organism and provides a quantitative analysis of the lipid content in that sample. Sperm cells are composed of various lipids, each with their unique contribution to the overall function of the cell. Lipidomics has already been used to find new and exciting information regarding the fatty acid content of sperm cells from different species. While the applications of lipidomics are rapidly evolving, gaps in the knowledge base remain unresolved. Current limitations of lipidomics studies include the number of available samples to analyze and the total amount of cells within those samples needed to detect changes in the lipid profiles across different subjects. The information obtained through lipidomics research is essential to systems and cellular biology. This review provides a concise analysis of the most recent developments in lipidomic research. This scientific resource is important because these developments can be used to not only combat the reproductive challenges faced when using cryopreserved semen and artificial reproductive technologies in livestock such as cattle, but also other mammals, such as humans or endangered species.

Freeze-thawing impairs the motility, plasma membrane integrity and mitochondria function of boar spermatozoa through generating excessive ROS

Background

Cryopreservation is an efficient way to store spermatozoa and is closely associated with the quality of sperm after the freeze-thaw process. During freeze-thaw cycling, excessive reactive oxygen species (ROS) are produced, and the effects of ROS on boar sperm during cryopreservation have not been identified.

Results

In this study, we evaluated the quality of boar spermatozoa in different steps of cryopreservation (extension, cooling, and thawing for 30 min and 240 min) with or without boar-sperm antioxidant (N-acetylcysteine (NAC)). The ROS levels, sperm motility, plasma membrane integrity, mitochondrial activity, sperm chromatin structure, ATP content, and sperm apoptosis were assayed. After thawing, the ROS level and sperm apoptosis were significantly increased, and the sperm motility, plasma membrane integrity, mitochondrial activity, sperm chromatin structure, and ATP content were significantly impaired compared with those at the extension period and cooling period. Moreover, the addition of N-acetyl L-cysteine (NAC) reversed these changes.

Conclusion

The freeze-thawing of boar spermatozoa impaired their motility, plasma membrane, mitochondrial activity, sperm chromatin structure and apoptosis by producing excessive ROS. Thus, the downregulation of ROS level by antioxidants, especially the NAC, is important for manufacturing frozen pig sperm to increase reproductive cells and livestock propagation, as well as to improve the application of frozen semen in pigs worldwide.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12917-021-02804-1.

Increased quality of in natura and cryopreserved semen of water buffaloes supplemented with saturated and unsaturated fatty acids from the palm oil industry

Ruminant energy supplementation with vegetable oils or fats has been standing out worldwide and oil palm processing has been receiving growing interest. This study assessed the effect of supplementation with saturated and unsaturated fatty acids from the palm oil industry on the lipid profile of seminal plasma and of the sperm membrane, as well as on the morphological and functional characteristics of raw and cryopreserved buffalo semen. Twelve purebred Murrah bulls (Bubalus bubalis) were assigned to the experimental groups and fed diets for 120 days with no added lipids (CONT, four bulls), or with an extra amount of 3% lipids from crude palm oil (PALM, four bulls), or from palm oil deodorizer distillate (PODD, four bulls). Semen was collected and cryopreserved every 15 days. The lipid composition of membranes and semen quality were determined after collections. Lipid supplementation did not impact feed intake (P>0.05). Diet enrichment with PALM increased the linoleic acid (C18:2,ω6) in seminal plasma. Lipid supplementation did not increase the polyunsaturated fatty acids in the sperm membrane composition, but significantly increased the lignoceric acid (C24:0). Cryopreserved semen of the supplemented bulls presented higher progressive motility (60.2 vs. 67.9 vs. 65.2%; P<0.05) and sperm viability detected by eosin-nigrosin staining (61.1 vs. 69.4 vs. 67.8%; P<0.05). Palm oil reduced major sperm defects in both raw (12.2 vs. 9.3 vs. 13.2%; P<0.0001) and cryopreserved semen (12.4 vs. 9.4 vs. 11.2%; P<0.0001). The lipids added to the diet did not impact the population of spermatozoa with intact plasma and acrosomal membranes (PI-/PSA-), but significantly increased the percentage of spermatozoa with high mitochondrial potential (25.6 vs. 31.5 vs. 32.0%; P=0.008). The results suggest that lipid supplementation based on crude palm oil or palm oil deodorizer distillate can be safely used to feed buffalo bulls and may increase sperm attributes related to male fertility.

Dietary flaxseed oil improve boar semen quality, antioxidant status and in-vivo fertility in humid sub-tropical region of North East India

Environmental stress in the form of high temperature humidity index (THI) in tropical and sub-tropical region negatively affects semen quality and fertility of boar. Therefore, the present study was done to evaluate the effect of supplementing flaxseed oil (FLO) to boar's diet on its semen quality, antioxidant status, fatty acid composition of seminal plasma and fertility under sub-tropical climate. For this purpose, six Hampshire crossbreed (50% Hampshire and 50% Gunghroo) boars were divided into two groups i.e control (CON) and treatment (FLO). In FLO and CON group, flaxseed and vegetable oil, respectively, was top dressed at the rate of 3% in basal diets for each boar on daily basis for 16 weeks during monsoon season. A total of 60 ejaculates, comprising 30 ejaculates from each group (ten ejaculates from each boar) were collected. Semen samples were evaluated for sperm quality parameters (SQPs: motility, viability, abnormality, acrosomal integrity and Hypo-osmotic swelling test) and velocity attributes by computer assisted semen analysis (CASA) at fresh and after 72 h of preservation at 17 °C. Antioxidant (glutathione peroxidase; GPx, catalase; CAT, total antioxidant capacity; TAC and malondialdehyde; MDA) were analyzed in seminal plasma and serum. Fatty acid compositions of seminal plasma were analyzed by gas chromatography-mass spectrometry (GC-MS). In-vivo fertility study was also conducted. Reaction time and false mounts were significantly (p < 0.05) reduced in FLO group as compared to CON group. Semen quality parameters were significantly (p < 0.05) improved at fresh stage and after 72 h of liquid storage in FLO group as compared to CON group. Velocity attributes (VAP, VSL, VCL, ALH, BCF and LIN) were significantly (p < 0.05) higher in FLO group. Flaxseed oil supplementation significantly (p < 0.01) enhanced serum GPx and CAT concentration. Serum and seminal plasma MDA concentration decreased significantly (p < 0.01) in FLO group. Similarly, GPx, TAC and CAT were significantly (p < 0.01) elevated in seminal plasma of FLO group. The study revealed that feeding of flaxseed oil altered the fatty acid composition of seminal plasma and significantly (p < 0.05) improved the farrowing rate. In summary, flaxseed oil supplementation improved the semen quality parameters and fertility of boars in sub-tropical climate by improving the antioxidant capacity and altering the fatty acid composition of seminal plasma.

Escherichia coli membrane-derived oxygen-reducing enzyme system (Oxyrase) protects bubaline spermatozoa during cryopreservation

The objective of this study was to determine the effectiveness of deoxygenation of semen extender using Escherichia coli membrane-derived oxygen scavenger (Oxyrase) on post-thaw quality of buffalo (Bubalus bubalis) spermatozoa. Sixteen semen ejaculates, four each from four bulls, were each divided into five equal fractions, diluted using Tris-egg yolk extender supplemented with different concentrations of Oxyrase (0, 0.3, 0.6, 0.9, and 1.2 U/ml), designated as treatments T1, T2, T3, T4, and T5, respectively, and cryopreserved. Immediately after thawing, Oxyrase did not improve sperm kinetics and motility; however, it improved the keeping quality (significantly lower deterioration of post-thaw sperm motility after incubation for 120 min) in T3. Further, T3 reduced (p < .05) cholesterol efflux and protected the intactness of the sperm plasma membrane. Flow cytometry with Fluo-3 AM/propidium iodide (PI) dual staining revealed the highest (p < .05) proportion of live spermatozoa with low intracellular calcium in T3. Oxyrase supplementation protected spermatozoa from premature capacitation which was confirmed by low expression of tyrosine-phosphorylated proteins (32, 75, and 80 kDa) and a relatively lower percentage of F-pattern (uncapacitated spermatozoa) in chlortetracycline assay. Importantly, the Oxyrase fortification decreased superoxide anion in a dose-dependent manner indicating reduced availability of oxygen at sperm mitochondrial level. Similarly, in Oxyrase-fortified sperm, malondialdehyde concentration, an index of lipid peroxidation, is also reduced in a dose-dependent manner. In conclusion, we demonstrate that deoxygenation of buffalo semen by Oxyrase has the potential of improving post-thaw sperm quality by overcoming the problem of cryocapacitation and oxidative damage during cryopreservation process.

Inclusion of ovine enriched serum with vitamin E and polyunsaturated fatty acids in the freezing medium: a new strategy to improve human frozen-thawed sperm parameters

The objective was to evaluate the effect of inclusion of 2.5% and 5% ovine serum, enriched with vitamin E (Vit E) and fish oil (FO), in human sperm freezing medium. Serum samples were prepared from sixteen rams (n = 4) feeding on a without supplemented diet, and diets supplemented with Vit E, FO and Vit E + FO. Semen samples, from 60 normozoospermic men, were frozen in: (I) a commercial freezing medium (SpermFreeze™; control medium), (II) the commercial freezing medium containing foetal bovine serum, (III) the commercial freezing medium + nonenriched serum (serum group), (IV) the commercial freezing medium + Vit E enriched serum (Vit E group), (V) the commercial freezing medium + FO enriched serum (FO group) and (VI) the commercial freezing medium + Vit E + FO enriched serum (Vit E + FO group). Sperm total and progressive motility, morphology, viability and plasma membrane integrity were significantly higher (p ≤ .05) in Vit E and Vit E + FO groups compared with the control group. Mitochondrial membrane potential did not differ between treatments (p > .05). It was concluded that ovine serum enriched with vitamin E and vitamin E + FO improved the quality of human spermatozoa but enriched serum containing FO could not improve the sperm cryo-injuries.

Conjugated linoleic acid as a potential bioactive molecule to modulates gamete and embryo cryotolerance

Abstract Conjugated linoleic acid (CLA) is a mixture of positional isomers of linoleic acid found in meat and dairy products from ruminants. It is a trans fat widely used by athletes as a food supplement, due to a supposed effect of maximizing the use of body fat reserves. The interest in diet and culture media supplementation with CLA is an emerging area, demanding studies in order to elucidate its benefits in the reproductive parameters, as well as in cryopreservation. Therefore, the aim of this review was to discuss the effects of CLA on the oocytes, sperm and embryos cryotolerance. Some studies have already demonstrated its use in cryopreservation of germline. Among those, it was observed that CLA supplementation during oocyte in vitro maturation can increase their viability post-freezing and developmental capacity. Regarding the use of CLA on sperm, there are few studies and their results are still inconclusive. Finally, studies about CLA supplementation on embryo culture media have shown promising results, indicating that this bioactive molecule is able to modulate lipid uptake on blastomeres. Altogether, these findings demonstrate the potential use of CLA as a bioactive molecule to improve germline and embryo cryotolerance and open new perspectives on human and animal reproduction field.

Recombinant peptide reverses cryo-capacitation in ram sperm and improves in vitro fertilization

Semen cryopreservation is a very important technique for assisted reproduction; however, the cryopreservation process is harmful because it results in a reduction in sperm motility and viability, and leads to premature signals of capacitation, resulting in lesser than desirable fertility rates after artificial insemination. A fraction of seminal plasma, enriched in proteins that contain type II fibronectin domains (FNII) can reverse molecular indicators of cryo-capacitation. The beneficial effects of these proteins, however, depend on the relative abundance in seminal plasma. To create a safe additive for improving frozen sperm functionality, in the present study there was cloning and expression of a recombinant peptide containing four FNII domains (named TrxA-FNIIx4-His6) and evaluation of its effect after addition to frozen/thawed ram sperm. The cDNA for this protein was expressed in E. coli and after denaturation and re-naturalization of the protein, toxicity and binding capacity were assessed. By fluorescent labelling assessment, there was binding of the protein to the thawed sperm. At the two doses used (0.15 and 0.3 μM), TrxA-FNIIx4-His6 had the capacity to reverse the molecular indicators of cryo-capacitation as indicated by the reduction on phosphorylated substrates of PKA. Furthermore, the supplementation with this protein resulted in a normal capacitation process as evidenced by the increase in the in vitro fertilization rate when the greatest concentration of the protein was evaluated (73.25 ± 2.95; 40.13 ± 11.82 for 0.3 μM and control, respectively). There was no effect of protein supplementation on sperm objective motility compared to untreated sperm. In conclusion, the use of TrxA-FNIIx4-His6 is a promising biotechnological approach for cryopreserving ram sperm and maintaining sperm viability.

Antioxidant Effect of a Polyphenol-Rich Murtilla (Ugni molinae Turcz.) Extract and Its Effect on the Regulation of Metabolism in Refrigerated Boar Sperm

The production of reactive oxygen species (ROS) in boar spermatozoa increases in refrigeration; this can have an impact on sperm quality and fertilization capacity. We evaluated the effect of polyphenol-rich aqueous extract of murtilla (Ugni molinae Turcz) on boar sperm stored at 17°C in order to reduce oxidative stress and improve sperm quality in the long term. Five experiments were performed: first, characterization of the polyphenol content from five genotypes of murtilla; second, determination of the genotype with the best antioxidant effect (MT-Ex); third, the antioxidant capacity on O₂⁻ and lipid peroxidation; fourth, the influence of MT-Ex on motility, calcium movement, cAMP, and metabolic parameters; and fifth, analysis of long-term refrigeration. The average phenolic content was 344 ppm; gallic acid, catechin, quercetin, myricetin, and kaempferol were detected. All extracts evaluated presented a concentration-dependent antioxidant effect. MT-Ex reduces intracellular O₂⁻/peroxides but low lipid peroxidation. MT-Ex in nonstimulated ROS conditions reduces sperm motility, mitochondrial membrane potential, cAMP, and ATP, but the succinate dehydrogenase activity remained normal; also, we observed a reduction in calcium movement in in vitro sperm capacitation. The long-term analyses showed that MT-Ex improved sperm motility decay and reduced membrane damage and ROS at 168 h. Based on this study, we propose MT-Ex as a supplement in semen extenders.

In vitro supplementation with unsaturated fatty acids improves boar sperm viability after storage at 6 °C

Liquid preservation of the cold-sensitive boar sperm at a lesser temperature than the standard 17 °C would reduce bacterial growth and minimize the use of antibiotics. There was assessment, therefore, of the capacity of individual fatty acids bound to fatty acid free BSA to improve sperm survival at 6 °C because oxidative stress and lipid degradation are prominent detrimental factors. Different effects of the fatty acids were observed. Supplementation with naturally occurring fatty acids (linolenic, linoleic, oleic, palmitoleic acid), which may become metabolically incorporated into sperm lipids, increased the number of motile and progressively motile sperm after 2 days of storage during a thermo-resistance test (5 h at 38 °C) to that of control samples preserved at 17 °C in pure Beltsville Thawing Solution. With the exception of linolenic acid, all naturally occurring fatty acids enhanced the number of sperm with active mitochondria after 3 days of storage. Palmitoleic acid was the most effective supplement with effects already present when sperm were re-warmed for 30 min after 2 and 7 days of storage. The non-endogenous, non-integrated timnodonic acid (20:5) had no effect on sperm variables. Because the application of individual fatty acids attached to BSA had differing effects in preserving boar sperm at 6 °C, the use of combinations of fatty acids could be more efficacious than with use of natural lipid supplements for low temperature preservation of sperm.

Influence of omega-3 incorporation in sperm preservation medium on physical and kinematic properties of chilled and cryopreserved ram spermatozoa

Two experiments were carried out to investigate the efficiency of supplementing sperm preservation medium with omega-3 polyunsaturated fatty acids on improving liquid-chilled storage and cryopreservation capacity of ram spermatozoa. Ejaculates (n = 100) were collected from five adult rams, Ovis aries, by an artificial vagina twice weekly throughout the period February-April, 2017. After initial evaluation, ejaculates of each collection session from the same males were pooled, diluted (1:10) with Tris-citric acid egg yolk extender, and were further split into five aliquots using a split-sample technique. The first aliquot served as control (omega-free), whereas the other four portions were supplemented with 0.1, 0.2, 0.3 or 0.4 mM omega-3, respectively (T₀ ). Thereafter, the diluted specimens were stored at 4°C for 48 hr, during which sperm physical and morphometric properties were evaluated along with oxidative stress indices (T₂₄ , T₄₈ ). Omega-3 levels that efficiently mitigated the detrimental effects of chilled preservation, and maintained preservation aptitude of spermatozoa were further investigated for sperm cryosurvival against control (untreated). Post-thaw physical and kinematic properties of spermatozoa, in all groups, were objectively evaluated by a computer-assisted sperm analysis (CASA) system. The results showed that, at 48 hr of chilled storage, supplementing preservation medium with 0.4 mM omega-3 was positively correlated (p < 0.01) with each of progressive motility, live sperm, intact acrosome and intact cell membrane (r = 0.83, 0.85, 0.85, 0.89, respectively). Furthermore, a positive correlation (p < 0.01) was observed between inclusion of omega-3 in cryopreservation medium and each of post-thaw total sperm motility, progressive motility, live sperm, normal sperm, intact acrosome, intact cell membrane, VCL, VSL, VAP, ALH and STR (r = 0.76, 0.84, 0.79, 0.90, 0.89, 0.91, 0.61, 0.73, 0.65, 0.78 and 0.60, respectively). These results accentuate efficiency of supplementing the diluent with omega-3 fatty acids on improving chilled and cryopreservation aptitude of ram spermatozoa.

Sperm cryopreservation: A review on current molecular cryobiology and advanced approaches

The cryopreservation of spermatozoa was introduced in the 1960s as a route to fertility preservation. Despite the extensive progress that has been made in this field, the biological and biochemical mechanisms involved in cryopreservation have not been thoroughly elucidated to date. Various factors during the freezing process, including sudden temperature changes, ice formation and osmotic stress, have been proposed as reasons for poor sperm quality post-thaw. Little is known regarding the new aspects of sperm cryobiology, such as epigenetic and proteomic modulation of sperm and trans-generational effects of sperm freezing. This article reviews recent reports on molecular and cellular modifications of spermatozoa during cryopreservation in order to collate the existing understanding in this field. The aim is to discuss current freezing techniques and novel strategies that have been developed for sperm protection against cryo-damage, as well as evaluating the probable effects of sperm freezing on offspring health.

Effects of adding egg yolks of different avian species to Tris glycerol extender on the post-thawing quality of buck semen

The effects of adding egg yolks (EY) of different avian species to the Tris glycerol extender was evaluated for post-thawing quality of buck semen. The semen samples collected from seven Aardi bucks were pooled and diluted 1:4 with the Tris glycerol diluents containing the egg yolks of chicken (C), pigeon (P), goose (G), Japanese quail (Q), duck (D), or turkey (T). The diluted semen samples were gradually cooled to 5 °C within 2 h, equilibrated at 5 °C for 2 h, and then frozen in liquid nitrogen vapor for 8 min before storing them at -196 °C. The frozen straws were thawed at 37 °C for 30 s and evaluated for sperm motility, vitality, abnormality, plasma-membrane integrity, and DNA fragmentation. The malondialdehyde (MDA) and reduced glutathione (GSH) activities were measured. The egg yolk samples of the above-mentioned avian species (n = 7/species) were analyzed for moisture, ash, protein, fatty acid (FA), and trace element contents. The use of the chicken EY (C) diluent resulted in better post-thawing buck semen quality, including the total progressive sperm motility parameters, sperm vitality, plasma membrane intactness, DNA integrity, and sperm abnormalities percentages, in comparison with the EY diluents of the other avian species. The lowest MDA and the highest GSH activities were observed in the C diluent. The chicken EY had the highest percentages of margaric and linolenic FAs and the lowest percentages of palmitoleic and myristic FAs. Moreover, the percentage of oleic FA was lower in the chicken EY than in the EYs of other species, except turkey. Additionally, the chicken EY had the significantly lowest concentration of Cu, Zn, Fe, and Mn. In conclusion, the use of chicken egg yolk extender is recommended for buck semen cryopreservation. The egg yolks of the other avian species studied cannot substitute the chicken EY as they gave poorer post-thawing semen quality. The EY composition, especially FA profile and trace elements concentration, significantly affected the post-thawing quality of buck semen.

Beneficial and harmful effects of cyclodextrin-vitamin E complex on cryopreserved ram sperm

Vitamin E is a potent molecule, especially when loaded in cyclodextrin, in modulating oxidative stress during the freeze-thawing process. The present study aimed to investigate the effect of different concentrations of cyclodextrin-vitamin E complex (CD-Vit E) on cryopreserved ram sperm. Ejaculates collected from five adult rams were pooled and divided into four aliquots. All aliquots were treated in Tris-extender (Tris-glucose-citric acid) containing 2 mg cholesterol-loaded methyl-β- cyclodextrin/120 × 10⁶ spermatozoa and either 0 (Control), 2, 4 or 6 mg CD-Vit E/120 × 10⁶ spermatozoa, corresponding to 0, 0.5, 1 or 1.5 of pure vitamin E, respectively. After incubation at 22 °C for 15 min and the addition of Tris-extender containing glycerol and egg yolk (v/v), all aliquots were frozen in liquid nitrogen. After thawing, motility (computer aided sperm analysis), viability (eosin staining), membrane integrity (HOST), acrosome integrity (Coomassie G-250 staining) and lipid peroxidation (Thiobarbituric acid assay) were evaluated. Compared to control, 2 mg CD-Vit E had a significant positive effect on total motility, progressive motility, movement linearity (LIN%), viability and lipid peroxidation. At 4 mg, however, CD-Vit E had a significant negative effect on total motility, progressive motility, membrane functionality and acrosome integrity. At a greater concentration (6 mg), the negative effects were greater as compared with inclusion of 4 mg in the cryoprotectant and the percentage of rapidly and moderately motile gametes and viability were also altered. In conclusion, the effect of CD-Vit E on cryopreserved ram sperm was concentration-dependent with the 2 mg amount having a beneficial effect while greater concentrations (4 and 6 mg) had a harmful effect on sperm motility and gamete integrity but without affecting oxidative stress status.

Evaluation of α-linolenic acid for freezability and in vivo fertility of Nili Ravi (Bubalus bubalis) buffalo semen

Alpha linolenic acid (ALA) is integral component of cell membrane that protects the cell in stressful events and involves in many metabolic pathways. It was hypothesized that ALA have the ability to protect the structural and functional integrity of buffalo spermatozoa during freeze-thawing. Therefore, study was designed to evaluate ALA supplementation (0, 5, 10 and 20 ng/mL) in extender on freezability and in vivo fertility of buffalo bull spermatozoa. Semen from three adult Nili-Ravi buffalo bulls of similar age was collected with artificial vagina (42 °C) for five weeks (replicates; N = 30). Qualified semen ejaculates (>1 mL volume, >60% motility; >0.5 billion/mL concentration) were diluted with tris-citric acid extender containing 0.0 (control), 5.0, 10.0 and 20.0 ng/mL ALA at 37 °C and cryopreserved following established protocol. Sperm motility and plasma membrane integrity were recorded higher (P < 0.05) in extender containing 5.0 ng/mL of ALA compared to control. Nevertheless, sperm viability, live dead ratio and chromatin integrity were observed higher (P < 0.05) in all experimental extenders with ALA compared to control. The number of abnormal sperm reduced significantly in all experimental extenders having ALA. A total of 539 artificial inseminations were performed with the best evolved extender having ALA (5.0 ng/mL; 272 inseminations) and control (267 inseminations). In vivo fertility rates of buffalo semen were recorded higher (P < 0.05) with extender containing ALA (5.0 ng/mL) (58%) compared to control (46%). In conclusion, supplementing 5.0 ng/mL ALA in extender improved the post-thaw quality and in vivo fertility of cryopreserved Nili-Ravi buffalo bull semen.

Polyunsaturated Fatty Acids in Male Ruminant Reproduction - A Review

Fatty acids such as n-3 and n-6 polyunsaturated fatty acids (PUFA) are critical nutrients, used to improve male reproductive performance through modification of fatty acid profile and maintenance of sperm membrane integrity, especially under cold shock or cryopreservation condition. Also, PUFA provide the precursors for prostaglandin synthesis and can modulate the expression patterns of many key enzymes involved in both prostaglandin and steroid metabolism. Many studies carried out on diets supplemented with PUFA have demonstrated their capability to sustain sperm motility, viability and fertility during chilling and freezing as well as improving testis development and spermatogenesis in a variety of livestock species. In addition to the type and quantity of dietary fatty acids, ways of addition of PUFA to diet or semen extender is very crucial as it has different effects on semen quality in male ruminants. Limitation of PUFA added to ruminant ration is due to biohydrogenation by rumen microorganisms, which causes conversion of unsaturated fatty acids to saturated fatty acids, leading to loss of PUFA quantity. Thus, many strategies for protecting PUFA from biohydrogenation in rumen have been developed over the years. This paper reviews four aspects of PUFA in light of previous research including rumen metabolism, biological roles, influence on reproduction, and strategies to use in male ruminants.

Effect of different concentrations of egg yolk and virgin coconut oil in Tris-based extenders on chilled and frozen-thawed bull semen

The aim of this study was to evaluate the effects of 8% virgin coconut oil (VCO) combined with different percentages of egg yolk in Tris extender on the quality of chilled and frozen-thawed bull semen. A total of 24 ejaculates from four bulls were collected using an electroejaculator. Semen samples were diluted with 8% VCO in Tris extender which contained different concentrations 0% (control), 4%, 8%, 12%, 16% and 20% egg yolk. The diluted semen samples were divided into two fractions: one was chilled and stored at 4°C until evaluation after 24, 72, and 144h; the second fraction was processed by chilling for 3h at 4°C to equilibrate, then packaged in 0.25ml straws and frozen and stored in liquid nitrogen at -196°C until evaluation after 7 and 14 days. Both chilled and frozen semen samples were then thawed at 37°C and assessed for general motility using computer-assisted semen analysis (CASA), viability, acrosome integrity, and morphology (eosin-nigrosin), membrane integrity (hypo-osmotic swelling test) and lipid peroxidation (thiobarbituric acid-reactive substances (TBARS)). The results indicate treatments with 8%, 12%, 16% and 20% egg yolk with 8% VCO had greater sperm quality (P<0.05) as compared with the control. The treatment with 20% egg yolk had the greatest sperm quality (P<0.05) among the treated groups for both chilled and frozen-thawed semen. In conclusion, the use of 8% VCO combined with 20% egg yolk in a Tris-based extender enhanced the values for chilled and frozen-thawed quality variables of bull sperm.

Effect of dietary fish oil with or without vitamin E supplementation on fresh and cryopreserved ovine sperm

This study was carried out to determine whether dietary fish oil (FO) with or without vitamin E (VE) supplementation would have a beneficial effect on characteristics of fresh and cryopreserved ovine sperm. Sixteen rams were allotted to four groups and fed one of the four diets: control diet (CON; without FO and VE supplementation), VE diet supplying 200 IU VE/day.ram, FO diet containing 2.5% (dry matter basis) FO, and OVE diet containing FO and VE. Semen samples were collected at Weeks 7, 9 and 11 for evaluation of seminal quality. Frozen samples from Weeks 9 and 11 were subjected to computer-assisted semen analysis (CASA). Seminal volume, percentage of sperm with normal morphology and intact acrosome and seminal concentration of malondialdehyde were increased in FO rams (P < 0.05). In VE rams, semen volume and percentage of morphologically normal sperm were higher compared with CON rams; however, in OVE rams these attributes were not different from those in CON rams. Other traits in fresh semen were not affected by the diet. Fish oil alone negatively affected the sperm viability, but not motility, of the frozen–thawed semen; however, simultaneous supplementation with FO and VE resulted in increased percentage of morphologically normal sperm, motility, and viability. The percentages of CASA type A (showing rapid progressive motility) and type B (showing medium progressive motility) sperm were higher in OVE compared with other groups. Vitamin E supplementation decreased the beat-cross frequency values compared with other groups. Other CASA parameters were not affected by the diets. In conclusion, dietary FO and VE in the breeding season of ram, generally, do not cause significant changes in fresh sperm quality but, for cryopreservation of sperm, supplementation of the diet with an antioxidant such as VE may be beneficial when polyunsaturated fatty acids are added to the diet.