Hydroxytyrosol effectively improves the quality of pig sperm at 17 °C

Incubating frozen-thawed buffalo sperm with olive fruit extracts counteracts thawing-induced oxidative stress and improves semen quality

Freezing-thawing procedures and semen manipulation for in vitro fertilization induce oxidative stress, which in turn leads to impaired sperm quality. The aim of this study was to evaluate whether incubation of frozen-thawed buffalo semen with olive fruit extracts (OFE), known to contain a high concentration of phenolic antioxidants, would improve semen quality by reducing oxidative stress. Frozen sperm (4 ejaculates/4 bulls/3 replicates) were thawed and diluted to 30 × 106/mL in IVF medium with 0, 72, 143, and 214 μL/mL of OFE, corresponding to 0 (D0-control), 50 (D50), 100 (D100), and 150 (D150) μM hydroxytyrosol. Sperm viability, acrosome integrity, membrane functionality, motility, and sperm kinetics were evaluated immediately after thawing (T0) and after 1 (T1) and 2 h (T2) of incubation at 38.7 °C. Based on the results, sperm biological antioxidant potential (BAP) and ROS levels (ROMs) were assessed in D0 and D100 groups at T1 and T2. To assess the effect of OFE on fertilizing ability, heterologous penetration rates were also evaluated, using bovine abattoir-derived oocytes. The treatment with OFE at all concentrations tested increased (P < 0.05) the percentage of acrosome intact spermatozoa compared to the D0-control at T1, but the effect was more evident (P < 0.01) with D100 (54.5 ± 3.0, 60.5 ± 1.5, 65.2 ± 3.3, and 62.5 ± 1.7, with D0, D50, D100, and D150 OFE, respectively). Total motility, progressive motility, rapid velocity, and progressive velocity decreased (P < 0.05) at T2 only in the D0-control group. The percentage of rapidly progressive sperm and the progressive motility tended to increase (P < 0.10) at T1 and T2, respectively, in D100 compared to D0 (24.7 ± 4.1 vs 16.4 ± 1.6 and 22.8 ± 2.7 vs 17.0 ± 1.2, respectively). The treatment with D100 OFE of frozen-thawed sperm increased (P < 0.05) some kinetic parameters (VAP and WOB). Spermatozoa incubated with D100 OFE exhibited higher (P < 0.01) total and normospermic oocyte penetration rates compared to D0 (86.5 ± 1.4 vs 78.5 ± 0.7, and 70.6 ± 1.5 vs 63.8 ± 1.1, respectively). Additionally, D100 OFE increased sperm BAP concentrations at both T1 and T2, while ROS levels were unaffected. These results suggest that incubating frozen-thawed buffalo semen with OFE is an effective strategy for preserving semen quality and in vitro fertilization ability by enhancing sperm antioxidant capacity.

Effects of hydroxytyrosol on post-thaw quality of rooster sperm

Semen cryopreservation is one of the most important reproduction techniques in the livestock and poultry industry. Cryopreservation induces cold stress, generating reactive oxygen species (ROS) and oxidative stress causing structural and biochemical damages in sperm. In this study, we evaluated the effects of the hydroxytyrosol (HT), as an antioxidant, at the concentrations of 0, 25, 50, and 100 μg/mL on post-thaw semen quality metrics in rooster. Semen samples were collected twice a week from 10 roosters (29 weeks), processed and frozen according to experimental groups. Different quality parameters, including total motility, progressive motility, viability, morphology, membrane integrity, and malondialdehyde were measured after thawing. Results showed that 25 and 50 μg/mL of HT produced the highest percentage of total motility (51.01 ± 2.19 and 50.15 ± 2.19, respectively) and progressive motility (35.74 ± 1.34 and 35.15 ± 1.34, respectively), membrane integrity (48.00 ± 2.18 and 46.75 ± 2.18, respectively) as well as viability (53.00 ± 2.17 and 52.50 ± 2.17, respectively) compared with the other groups (p < .05). The group with 25 μg/mL of HT showed the lowest significant (p < .05) MDA concentration (1.81 ± 0.25). Our results showed that the effect of HT was not dose-dependent and optimum concentration of HT could improve functional parameters of rooster sperm after freezing-thawing. These findings suggest that HT may have protective effects on the rooster sperm during the freezing-thawing process.

Supplementing Boar Diet with Nicotinamide Mononucleotide Improves Sperm Quality Probably through the Activation of the SIRT3 Signaling Pathway

Sperm quality is an important indicator to evaluate the reproduction ability of animals. Nicotinamide mononucleotide (NMN) participates in cell energy metabolism and reduces cell oxidative stress. However, the effect and regulatory mechanism of NMN on porcine sperm quality are still unknown. Here, 32 Landrace boars were randomly assigned to four groups (n = 8) and fed with different levels of NMN (0, 8, 16 or 32 mg/kg/d) for 9 weeks, and then serum and semen samples of the boars were collected to investigate the function and molecular mechanism of NMN in sperm quality. The results showed that the dietary NMN supplementation significantly increased sperm volume, density and motility (p < 0.05). Interestingly, NMN apparently improved the antioxidative indexes and increased the levels of testosterone (p < 0.05) in serum. Furthermore, NMN upregulated the protein levels of sirtuin 3 (SIRT3), antioxidation and oxidative phosphorylation (OXPHOS), but downregulated the protein levels of apoptosis in semen. Mechanically, NMN protected sperm from H2O2-induced oxidative stress and apoptosis through SIRT3 deacetylation. Importantly, the SIRT3-specific inhibitor 3-TYP attenuated the antioxidation and antiapoptosis of NMN in sperm. Therefore, NMN exerts antioxidation and antiapoptosis to improve boar sperm quality via the SIRT3 signaling pathway. Our findings suggest that NMN is a novel potential boar antioxidative feed additive to produce high-quality porcine semen.

Evaluation of the effects of hydroxytyrosol on human sperm parameters during cryopreservation

Human sperm cryopreservation is a routine procedure in assisted reproductive technology, but it has detrimental effects on different sperm parameters due to oxidative stress. Our objective was to assess the impacts of hydroxytyrosol (HT), as an antioxidant, on human sperm parameters following cryopreservation. In the first phase, 20 normal human semen samples were cryopreserved using the rapid freezing method with different concentrations of HT including 0, 50, 100, 150, and 200 μg/mL. In the second phase, 20 normal semen samples were collected and cryopreserved with 50 and 100 μg/mL HT. The beneficial effects of HT were determined by evaluation of motility (computer-assisted sperm analysis; CASA), viability (Eosin-nigrosine stain), DNA integrity (sperm chromatic dispersion test, SCD), reactive oxygen species (DCF and DHE staining by flowcytometry) lipid peroxidation (malondialdehyde, MDA test) and mitochondrial membrane potential (JC1 staining by flowcytometry) of sperm after cryopreservation. After thawing, sperm motility had an increasing trend in 50 and 100 μg/mL HT groups in comparison with other groups, althought the difference was not significant. However, sperm viability was significantly increased at 50 and 100 μg/mL HT. Our data also showed that sperm DNA fragmentation was significantly decreased after thawing at 100 μg/mL in comparison with 0 and 50 μg/mL HT. However, the level of intracellular reactive oxygen species, lipid peroxidation and mitochondrial membrane potential were not significantly different between groups. Our results showed that HT may have protective effects on the viability and DNA integrity of human sperm during the freezing-thawing process.

The multidrug-resistant Pseudomonas fluorescens strain: a hidden threat in boar semen preservation

Although the bacterial composition of boar ejaculate has been extensively studied, the bacterial composition of extended boar semen is often overlooked, despite the potential risks these microorganisms may pose to the long-term preservation of extended boar semen at 15-17°C. In this study, we characterized the bacterial community composition of extended semen and discovered that Pseudomonas spp. was the dominant flora. The dominant strains were further isolated and identified as a potential new species in the Pseudomonas fluorescens group and named GXZC strain, which had adverse effects on sperm quality and was better adapted to growth at 17°C. Antimicrobial susceptibility testing showed that the GXZC strain was resistant to all commonly used veterinary antibiotics. Whole-genome sequencing (WGS) and genome annotation revealed the large genetic structure and function [7,253,751 base pairs and 6,790 coding sequences (CDSs)]. Comparative genomic analysis with the closest type strains showed that the GXZC strain predicted more diversity of intrinsic and acquired resistance genes to multi-antimicrobial agents. Taken together, our study highlights a problem associated with the long-term storage of extended boar semen caused by a P. fluorescens group strain with unique biological characteristics. It is essential to develop a new antibacterial solution for the long-term preservation of boar semen.

Discriminant Analysis and Data Mining CHAID Decision Tree as Tools to Evaluate the Buffering Effect of Hydroxytyrosol on Reactive Oxygen Species in Rooster Sperm Cryopreservation

Sperm cryopreservation is effective in safeguarding genetic biodiversity in avian species. However, during this process, spermatozoa are very susceptible to plasma membrane peroxidation in the presence of high concentrations of reactive oxygen species (ROS). To mitigate this effect, the addition of exogenous antioxidants, such as hydroxytyrosol (3,4-dihydroxyphenylethanol; HT), an antioxidant derived from olive oil, to the cryopreservation sperm diluent, could be useful. To verify this, a cryopreservation diluent was supplemented with different concentrations (0 μg/mL, 50 μg/mL, 100 μg/mL, and 150 μg/mL) of HT. For this, semen was collected in 10 replicates from 16 roosters of the Utrerana avian breed, and a pool was prepared with the optimum quality ejaculates in each replicate. After cryopreservation, spermatozoa were thawed and different in vitro semen quality parameters were evaluated. A discriminant canonical analysis (DCA) was carried out and revealed that total motility (TM; Lambda = 0.301, F = 26,173), hypo-osmotic swelling test (HOST; Lambda = 0.338, F = 22,065), and amplitude of lateral head displacement (ALH, Lambda = 0.442; F = 14,180) were the variables with the highest discriminant power. Finally, a chi-squared automatic interaction detection (CHAID) decision tree (DT) was performed excluding fresh semen samples and ROS was found to be the most valuable variable to discriminate between the different established freezing groups. Samples in the absence of HT or with low concentrations of this antioxidant showed less desirable ROS values in cryopreserved rooster semen. The present study could lead to the improvement of cryopreservation techniques for the genetic material of local poultry breeds and optimize the conservation programs of endangered native avian breeds.

Animal board invited review: An update on the methods for semen quality evaluation in swine - from farm to the lab

Pig breeding is mainly conducted through artificial insemination with liquid-stored semen. It is, therefore, crucial to ensure that sperm quality is over the standard thresholds, as reduced sperm motility, morphology or plasma membrane integrity are associated with reduced farrowing rates and litter sizes. This work aims to summarise the methods utilised in farms and research laboratories to evaluate sperm quality in pigs. The conventional spermiogram consists in the assessment of sperm concentration, motility and morphology, which are the most estimated variables in farms. Yet, while the determination of these sperm parameters is enough for farms to prepare seminal doses, other tests, usually carried out in specialised laboratories, may be required when boar studs exhibit a decreased reproductive performance. These methods include the evaluation of functional sperm parameters, such as plasma membrane integrity and fluidity, intracellular levels of calcium and reactive oxygen species, mitochondrial activity, and acrosome integrity, using fluorescent probes and flow cytometry. Furthermore, sperm chromatin condensation and DNA integrity, despite not being routinely assessed, may also help determine the causes of reduced fertilising capacity. Sperm DNA integrity can be evaluated through direct (Comet, transferase deoxynucleotide nick end labelling (TUNEL) and its in situ nick variant) or indirect tests (Sperm Chromatin Structure Assay, Sperm Chromatin Dispersion Test), whereas chromatin condensation can be determined with Chromomycin A3. Considering the high degree of chromatin packaging in pig sperm, which only have protamine 1, growing evidence suggests that complete decondensation of that chromatin is needed before DNA fragmentation through TUNEL or Comet can be examined.

Hydroxytyrosol and resveratrol improves kinetic and flow cytometric parameters of cryopreserved bull semen with low cryotolerance

There is considerable interest in breeding programs to "rescue" semen with poor post-thaw fertility from bulls known as "bad freezers". We hypothesized that there may be an interaction between the post-thaw recovery of sperm and the efficacy of antioxidant addition to extenders. The current study assesses the effects of antioxidant additives hydroxytyrosol (HT) and resveratrol (RSV) on the post-thaw semen parameters in two groups of bulls classified as either high or low cryotolerant (i.e., "good" and "bad" freezers). Semen samples were collected from 40 bulls and processed in the extenders containing different concentrations of HT (experiment 1; 0, 25 and 50 µM) and RSV (experiment 2; 0.0, 0.01, 0.1 and 1 mM). In experiment 1, bulls in the low cryotolerance group had a significant improvement in post-thaw recovery at 25 µM and 50 µM (P < 0.05). These improvements were observed in motility and several cellular parameters. However, post-thaw semen quality in the high cryotolerance group was not significantly affected by the HT addition. In experiment 2, although RSV did not have any positive impact in high cryotolerance group, post-thaw recovery in the low cryotolerance bulls was significantly improved in 0.1 mM RSV. Oxidative stress markers in either high or low cryotolerance groups were not significantly changed by RSV addition (P > 0.05). It can be concluded that addition of optimized concentrations of HT and RSV to the extender could be a strategy for improving the post-thaw semen, especially in bulls with high genetic merit but low initial cryotolerance.