α-Linolenic acid supplementation in BioXcell® extender can improve the quality of post-cooling and frozen-thawed bovine sperm

A review of recent developments in the application of nanostructures for sperm cryopreservation

In the 1970s, sperm cryopreservation was presented as a unique route to fertility preservation. The ability to cryopreserve sperm from all species is challenging. The sperm cryopreservation process encompasses various cellular stresses such as increased osmotic pressure, ice crystal formation, and thermal shock, therefore decreasing the quality of sperm. The nanostructures due to their inherent features such as reactivity, high uptake, active surface area, and antioxidant activity, have contributed to modifying freezing protocols. In this review, the current state of the art with regards to emerging applications of nanotechnology in sperm cryopreservation are reviewed, some of the most promising advances are summarized, and the limitations and advantages are comprehensively discussed.

Effect of L-proline on sperm quality during cryopreservation of boar semen

L-proline has been reported to be useful in semen cryopreservation. However, its use has rarely been reported in the freezing of boar semen. The objective of this study was to evaluate the effects of different concentrations of L-proline (0, 10, 30, 50, and 90 mM) on the quality of boar semen after freezing and thawing. Semen samples from boars (n = 6) were frozen using freezing extenders with added concentrations of L-proline. Total sperm motility, progressive motility, survival time at 37 °C, acrosome integrity, mitochondrial activity, DNA integrity, the content of the lipid peroxidation product malondialdehyde (MDA), total antioxidant capacity (T-AOC) and, expression levels of apoptosis protein (cleaved caspase 3 and Bax) were evaluated after thawing. The results showed that total sperm viability (73.96% vs. 63.58%) and progressive motility (56.88% vs. 47.26%) after thawing were significantly higher in the 10 mM L-proline treatment group than in the control group. The survival time at 37 °C and the total motility of sperm in the 10 mM group within one hour after thawing were significantly higher than in the control group. Acrosome integrity and mitochondrial activity of sperm in the 10 mM group were significantly higher than those in the control, 50 mM, and 90 mM groups. The DNA integrity rate in the 10 mM group was significantly higher than in the control group. The L-proline treatment did not affect sperm MDA content or T-AOC. The expression levels of apoptosis protein (cleaved caspase 3 and Bax) in the 10 mM L-proline supplemented group were lower than those in the control group. In conclusion, the freezing extender containing 10 mM L-proline improved semen quality after freezing and thawing and thus would be a useful reagent for boar semen cryopreservation.

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.

Bull Semen Obtained on Beef Farms by Electroejaculation: Sperm Quality in the First Two Hours of Storing with Different Extenders and Holding Temperatures

Sperm quality decreases over time, so bull semen may need to be preserved after field collection. However, the effect of handling such semen samples from commercial farms and placing them in very short-term storage has not been elucidated. Therefore, ejaculate from 25 bulls from 1 dairy and 14 beef cattle farms were collected under farm conditions and evaluated for semen quality during the first two hours after collection. Two commercial extenders (AndroMed^® and BIOXcell^®) and two different storage temperatures (5 °C and room temperature) were used to evaluate the influence on semen quality and sperm kinetics in ejaculates grouped into three evaluation times, based on time since collection (Time 1: <75 min, n = 7; Time 2: 75-105 min, n = 11; and Time 3: 105-120 min, n = 7). Classical semen parameters, sperm motion kinetics by CASA and colony-forming units were assessed. The differences between both extenders in curvilinear and straight-line velocities (VCL and VSL) for the different time groups (Time 2 and Time 3) were statistically significant for p < 0.05. AndroMed^® showed lower VSL, straightness and linearity in sperm compared to BIOXcell^® (p < 0.05). In conclusion, AndroMed^® induced more curvilinear movement, while BIOXcell^® stimulated straighter motility.

Regulation of semen quality by fatty acids in diets, extender, and semen

Fatty acids (FAs) are classified into different types according to the degree of hydrocarbon chain saturation, including saturated fatty acids (SFAs), monounsaturated fatty acids (MUFAs), omega-3 polyunsaturated fatty acids (omega-3 PUFAs) and omega-6 polyunsaturated fatty acids (omega-6 PUFAs), which play an important role in maintaining semen quality. This review focuses on the regulation of FAs in semen, diet and extender on semen quality, and expounds its effects on sperm motility, plasma membrane integrity, DNA integrity, hormone content, and antioxidant capacity. It can be concluded that there are species differences in the FAs profile and requirements in sperm, and their ability to regulate semen quality is also affected by the addition methods or dosages. Future research directions should focus on analyzing the FAs profiles of different species or different periods of the same species and exploring suitable addition methods, doses and mechanism of regulating semen quality.

Cryopreservation of Yak Semen: A Comprehensive Review

An urgent need to boost the sustainability and efficiency of animal production exists, owing to the growing global population. Enhancing the global fertility of animals, especially cattle, is essential to ameliorate this issue. Artificial insemination and sperm cryopreservation have a considerable and favorable influence on the quantity and quality of the cattle produced. Sperm cryopreservation is crucial for livestock production because it promotes and accelerates genetic diversity and the worldwide dispersion of animals with enhanced genetics. Owing to the importance of cryobiology in reproductive technologies, researchers are developing new approaches, and they are testing cryoprotectant drugs to enhance sperm cryosurvival. However, the viability of sperm after freezing is low and widely varies across breeding yaks. These faults are crucial because they impede advances in reproductive biotechnology and the study of mammalian gametes at a fundamental level. Using chemicals, researchers have developed and enhanced various extenders with varying degrees of efficiency to reduce cryodamage and oxidative stress. In this article, we review the cryopreservation of yak semen, the development of extenders, the difficulties faced during cryopreservation, and the evaluation of semen quality using various methodologies. This review might be helpful for researchers exploring semen cryopreservation in the future, as demand for enhanced cryopreservation exists to boost the post-thaw viability and fertility of sperm.

Effects of adding mixed chicken and quail egg yolks to the cryodiluent on the quality of ram semen before and after cryopreservation

The effects of adding mixed chicken and Japanese quail egg yolks (EYs) to the cryodiluent on the quality of ram semen before freezing and post-thawing were evaluated. Additionally, the composition of chicken and quail egg EYs and their mixture were analyzed for results explanation. The semen was collected from rams (n = 5) and extended with cryodiluent containing the EY of chicken, quail or their mixture (1:1). The extended semen was chilled slowly to 5 °C within 2 h and equilibrated for 2 h, before frozen on the liquid nitrogen vapor and cryopreserved at -196 °C. The straws were evaluated before freezing and post-thawing for sperm motility, vitality and abnormality besides plasma-membrane and DNA integrities. The moisture, ash, protein, and fatty acid (FA) contents of chicken EY, quail EY and their mixture were analyzed. Sperm vitality, plasma membrane integrity and DNA integrity before freezing were significantly (P < 0.05) higher in quail EY than chicken EY and mixed EYs cryodiluent. The chicken EY extender significantly improved the vitality, plasma membrane and DNA integrities of post-thawed ram semen in comparison with quail EY or mixed EYs extenders. While, the post-thawing sperm abnormalities was lower (P ≤ 0.05) in quail EY than chicken EY and mixed EYs cryodiluent. The post-thawing sperm motion kinetics parameters were higher in quail EY than chicken EY and mixed EYs cryodiluent. The highest percentages of moisture, ash, saturated fatty acids (SFAs) and monounsaturated fatty acids (MUFAs) were detected in quail EY had. While, the highest percentages of fat, protein and polyunsaturated fatty acids (PUFAs) were detected in chicken EY. In conclusion, using of chicken EY can improve total motility, vitality, plasma membrane integrity and DNA integrity of cryopreserved ram semen. While, using of quail EY can improve sperm abnormalities and kinetic motion parameters of cryopreserved ram semen. Mixing chicken and quail EYs added no value for post-thawing ram semen parameters.

Poultry genetic heritage cryopreservation and reconstruction: advancement and future challenges

Poultry genetics resources, including commercial selected lines, indigenous breeds, and experimental lines, are now being irreversibly lost at an alarming rate due to multiple reasons, which further threats the future livelihood and academic purpose. Collections of germplasm may reduce the risk of catastrophic loss of genetic diversity by guaranteeing that a pool of genetic variability is available to ensure the reintroduction and replenishment of the genetic stocks. The setting up of biobanks for poultry is challenging because the high sensitiveness of spermatozoa to freezing–thawing process, inability to cryopreserve the egg or embryo, coupled with the females being heterogametic sex. The progress in cryobiology and biotechnologies have made possible the extension of the range of germplasm for poultry species available in cryobanks, including semen, primordial germ cells, somatic cells and gonads. In this review, we introduce the state-of-the-art technologies for avian genetic resource conservation and breed reconstruction, and discuss the potential challenges for future study and further extending of these technologies to ongoing and future conservation efforts.

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.

Evaluation of Semen Quality of Jeju Black Cattle (JBC) to Select Bulls Optimal for Breeding and Establish Freezing Conditions Suitable for JBC Sperm

Simple Summary

Jeju black cattle, a type of native Korean cattle characterized by black fur covering the entire body, inhabit Jeju Special Self-Governing Province, a World Natural Heritage Site. Although this breed was state designated as a natural monument in 2013 due to its characteristics and genetic traits, it is on the verge of extinction and thus there is a need to preserve this breed and further improve its traits. Therefore, we evaluated sperm motility, vitality, and morphology, which have long been considered good predictors of fertility in the absence of female infertility factors. Our findings showed that the semen of the JBC-A bull was superior to the semen of four other JBC bulls. Due to the aging of the population of JBC breeding bulls, strategies should be devised to improve sperm production in vivo.

Abstract

To optimize the reproduction of Jeju black cattle (JBC), freezing conditions for sperm were established and sperm motility, vitality, morphology, and fertility were evaluated to select the optimal bull for breeding. Semen samples from five JBC bulls were individually mixed with freezing medium at a final concentration of 1 × 108 sperm/mL and frozen in liquid nitrogen vapor at a height of 3 or 7 cm (referred to as 3 cm sperm and 7 cm sperm, respectively). When the freezing conditions were compared, the motility of 7 cm sperm was significantly higher than that of 3 cm sperm for the JBC-A bull. The motility, curvilinear velocity, straight-line velocity, and average path velocity of fresh and frozen–thawed sperm were the highest for the JBC-A bull. The vitalities of fresh and frozen–thawed sperm were the highest for the JBC-A/E and JBC-A bulls, respectively. The percentage of normal cells in fresh sperm was the highest for the JBC-D bull. The rates of the normal formation of two pronuclei and total sperm penetration were the highest in zygotes fertilized with sperm from the JBC-A bull. The sperm from the JBC-A bull had superior qualities and are thus the most appropriate choice for the preservation and reproduction of these endangered cattle.

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.

Application of High Hydrostatic Pressure (HHP) to Improve Cryopreservation of Young Bull Semen

The objective of the study was to determine the effect of high hydrostatic pressure (HHP) on quality of cryopreserved semen of young bulls. Semen for this study was collected from 8 bulls aged between 13 and 18 months at monthly intervals, from June to September. After collection, semen was diluted in a commercial Bioxcell® extender (one part at 1:1 and a second part to give a sperm concentration of 20 million/0.2 mL), filled into straws and treated with HHP at 30 MPa for 90 min. After HHP treatment, pre-diluted semen (1:1) was diluted to a sperm concentration 20 million/0.2 mL and filled into straws. In addition, part of the semen diluted to a concentration of 20 million/0.2 mL was not treated with HHP (control). All of it was held at +4°C and frozen in a freezer after 2.5-h equilibration. Semen was thawed in a water bath at 38°C and subjected to estimation of the percentage of motile sperm both subjectively and using a computer-assisted semen analyzer and cytometric assessment of sperm cell membrane integrity. Subjective motility and fast progressive motility were significantly higher with pre-diluted (1:1) and HHP treated semen compared to control (P<0.05). No significant differences were observed in percentage of membraneintact spermatozoa between control and experimental groups. Additionally, the influence of HHP on the sperm of individual bulls was assessed. In bull number 2, the HHP treatment after semen pre-dilution significantly improved progressive motility from 54.1 to 63.4 percent (P<0.05). In bull number 4, the HHP treatment after semen pre-dilution significantly improved subjective motility, rapid motility and progressive motility by 12.5, 16.8 and 16.3 percent, respectively (P<0.05). No effect was seen for 6 bulls. It is concluded that for some bulls, the application of HHP before semen freezing may improve the cryopreservation outcome. However, this requires further research in this area, also to determine the fertilizing capacity of bull semen exposed to high hydrostatic pressure.

Semen extenders: An evaluative overview of preservative mechanisms of semen and semen extenders

Reproduction is fundamental for all living things as it ensures the continued existence of a species and an improved economy in animal husbandry. Reproduction has developed since history, and diverse processes, such as artificial insemination and in vitro fertilization, have been developed. Semen extenders were discovered and developed to protect sperm from harmful factors, such as freeze and osmotic shock, oxidative stress, and cell injury by ice crystals. Semen extenders preserve sperm by stabilizing its properties, including sperm morphology, motility, and viability and membrane, acrosomal, and DNA integrity. Therefore, semen extenders must provide a favorable pH, adenosine triphosphate, anti-cooling and anti-freeze shock, and antioxidant activity to improve semen quality for fertilization. Hence, this review provides precise data on different semen extenders, preservative mechanisms, and essential additives for semen extenders in different animals.

Effects of exogenous lactoferrin on characteristics and functions of bovine epididymal, ejaculated and frozen-thawed sperm

The purpose of this study was to investigate effects of addition of lactoferrin on characteristics and functions of bovine epididymal, ejaculated, and frozen-thawed sperm. The addition of lactoferrin was significantly (p < .05) effective on increasing values of progressive motility, straightness, and linearity in caput epididymal sperm and values of motility in cauda epididymal sperm. When ejaculated sperm were incubated in capacitation medium, percentages of motile and progressively motile sperm decreased largely within the first period of 30 min, followed by only minor changes. However, the addition of lactoferrin significantly lessened the early decreases of these parameters and additionally promoted capacitation-dependent changes of chlortetracycline staining patterns (from F pattern to B pattern). In other experiments, when ejaculated sperm were exposed to oxidative stress with 100-µM H₂ O₂ , the addition of lactoferrin partially protected them from dysfunction of flagellar movement and loss of progressive movement. In final experiments with frozen-thawed samples incubated in the capacitation medium, the addition of lactoferrin effectively survived dying sperm and suppressed occurrence of sperm agglutination. These results may suggest biological and biotechnological potentials of lactoferrin for modulation of bovine sperm viability, motility, capacitation state, and preservation in vitro.

Comparative analysis of various step-dilution techniques on the quality of frozen Limousin bull semen

Background and Aim:

Indonesia has two National Artificial Insemination centers and 17 Regional Artificial Insemination Centers. The frozen semen production techniques differed between the centers, including the type of diluent and semen dilution technique. The aim of the research was to compare the quality of frozen Limousin bull semen diluted using different techniques.

Materials and Methods:

Semen was collected from three sexually mature Limousin bulls using an artificial vagina. Immediately after collection, the semen was evaluated macroscopically and microscopically. Semen that had >70% motile sperm and <20% sperm abnormality was divided into three tubes and diluted with skim milk-egg yolk (SMEY) using three different dilution techniques: One-step dilution (100% SMEY with 8% glycerol) at room temperature ([RT] 20°C until 25°C) two-step dilution (50% SMEY without glycerol at RT, stored at 5°C; and 50% SMEY with 16% glycerol after 1 h stored at 5°C); and three-step dilution (50% SMEY without glycerol at RT, stored at 5°C; and 50% SMEY with 16% glycerol added twice at 1 h and 1.5 h after being stored at 5°C). The diluted semen was loaded into 0.25 mL mini straws, equilibrated, and frozen using a freezing machine. Sperm motility, viability, membranes, DNA integrity, and concentrations of malondialdehyde (MDA) and aspartate aminotransferase (AST) enzymes were evaluated after thawing.

Results:

The results showed that there were no significant differences in sperm motility and DNA integrity between dilutions (p>0.05). However, sperm viability and membrane intactness of one-step dilutions were higher than those of three-step dilutions. The concentrations of MDA and AST enzymes of sperm in one-step dilutions were lower than those of three-step dilutions (p<0.05).

Conclusion:

It was concluded that the one-step-dilution technique was better than three-step dilution for cryopreservation of Limousin bull semen.

The role of environmental optimization for storing bulls' sperm cells

Artificial insemination has achieved a dynamic increase in genetic progress, and this is due to the improvement of sperm preservation technology. In recent years, a lot of attention has been paid to optimizing bull sperm storage environment and objectifying methods of sperm quality analysis. This review presents bull sperm preservation methods and ways to modify their storage environment. The main purpose of sperm preparation for artificial insemination is to obtain sperm with a high percentage of viable, motile sperm with normal morphology and low DNA fragmentation rates. Currently conducted experiments indicate the possibility of improving the quality of insemination doses produced using various components enriching common diluents. However, despite extensive research, no better results have been achieved than obtaining insemination doses with sperm viability that exceeds just over 60%. Obtaining a very good quality of frozen semen seems to be still unachievable today.

Defining the male contribution to embryo quality and offspring health in assisted reproduction in farm animals

Assisted reproductive technologies such as artificial insemination have delivered significant benefits for farm animal reproduction. However, as with humans, assisted reproduction in livestock requires the manipulation of the gametes and preimplantation embryo. The significance of this ‘periconception’ period is that it represents the transition from parental genome regulation to that of the newly formed embryo. Environmental perturbations during these early developmental stages can result in persistent changes in embryonic gene expression, fetal organ development and ultimately the long-term health of the offspring. While associations between maternal health and offspring wellbeing are well-defined, the significance of paternal health for the quality of his semen and the post-conception development of his offspring have largely been overlooked. Human and animal model studies have identified sperm epigenetic status (DNA methylation levels, histone modifications and RNA profiles) and seminal plasma-mediated maternal uterine immunological, inflammatory and vascular responses as the two central mechanisms capable of linking paternal health and post-fertilisation development. However, there is a significant knowledge gap about the father’s contribution to the long-term health of his offspring, especially with regard to farm animals. Such insights are essential to ensure the safety of widely used assisted reproductive practices and to gain better understanding of the role of paternal health for the well-being of his offspring. In this article, we will outline the impact of male health on semen quality (both sperm and seminal plasma), reproductive fitness and post-fertilisation offspring development and explore the mechanisms underlying the paternal programming of offspring health in farm animals.

Optimization of sperm freezability in Bactrian camel using various dilution rates and equilibration times

The effect of different dilution rates and equilibration times on the cryopreservation of Bactrian camel spermatozoa was evaluated in the current study. Semen samples from four healthy adult males were collected, processed and pooled. They were then subjected to a completely randomized 4×2 factorial design including four dilution rates (DR; 1:1, 1:2, 1:4 or 1:8; v:v with SHOTOR diluent) and two equilibration times (ET; 1 or 2 h at 5ºC). After freezing and thawing, sperm kinematic parameters as well as viability, plasma membrane integrity, abnormality and seminal malondialdehyde level were assessed. According to the results, four-fold diluted samples recorded significantly higher values (P < 0.05) for sperm total (39.58 vs 31.83 and 33.33,%) and progressive motility (19.50 vs 14.00 and 14.25,%), viability (55.37 vs 43.50 and 48.75,%) and plasma membrane integrity (46.75 vs 37.25 and 37.37,%) than those of both less (1:1) and high (1:8) concentrated samples, respectively. By contrast, the percentage of abnormal spermatozoa and the concentration of seminal malondialdehyde were comparable among all treated groups. Moreover, ET revealed that 1 h equilibration had significantly higher sperm motility (37.04 vs 33.33%), linearity (42.29 vs 32.26%), beat cross-frequency (13.15 vs 8.70 Hz), plasma membrane integrity (42.25 vs 39.75%) and viability (51.37 vs 48.12%) compared with 2 h of ET (P < 0.05). Taken together, a four-fold dilution along with 1 h equilibration can be an optimal procedure to cryopreserve Bactrian camel sperm.

Advances in Cryopreservation of Bull Sperm

Cryopreservation of semen and artificial insemination have an important, positive impact on cattle production, and product quality. Through the use of cryopreserved semen and artificial insemination, sperm from the best breeding bulls can be used to inseminate thousands of cows around the world. Although cryopreservation of bull sperm has advanced beyond that of other species, there are still major gaps in the knowledge and technology bases. Post-thaw viability of sperm is still low and differs significantly among the breeding bulls. These weaknesses are important because they are preventing advances both in fundamental science of mammalian gametes and reproductive biotechnology. Various extenders have been developed and supplemented with chemicals to reduce cryodamage or oxidative stress with varying levels of success. More detailed insights on sperm morphology and function have been uncovered through application of advanced tools in modern molecular and cell biology. This article provides a concise review of progress in the cryopreservation of bull sperm, advances in extender development, and frontiers using diverse techniques of the study of sperm viability. This scientific resource is important in animal biotechnology because with the advances in discovery of sperm fertility markers, there is an urgent need to improve post-thaw viability and fertility of sperm through enhanced cryopreservation for precision agriculture to produce food animals to ensure food security on the global scale.

Effect of Alpha-Linolenic Acid with Bovine Serum Albumin or Methyl-Beta-Cyclodextrin on Membrane Integrity and Oxidative Stress of Frozen-Thawed Boar Sperm

The study was conducted to investigate the effects of alpha-linolenic acid (ALA) combined with bovine serum albumin (BSA) or methyl-beta-cyclodextrin (MBCD) on plasma and acrosomal membrane damages, mitochondrial activity, morphological abnormality, motility, and oxidative stress in frozen-thawed boar sperm. In previous our study, 3 ng/mL ALA had been shown protective effect during freezing process of boar sperm. Therefore, we used 3 ng/mL ALA in present study and ALA was combined with same molar ratio of BSA or MBCD (ALA+BSA and ALA+MBCD, respectively). To confirm the effect of two carrier proteins, same volume of BSA and MBCD without ALA were added during cryopreservation. Membrane damage, mitochondrial activity, reactive oxygen species (ROS) and lipid peroxidation (LPO) levels were measured using flow cytometry, and movement of sperm tail as motility parameter and morphological abnormality were observed under light microscope. In results, all of sperm parameters were enhanced by ALA combined with BSA or MBCD compared to control groups (p<0.05). Mitochondrial activity, morphological abnormality, ROS and LPO levels in ALA+BSA or MBCD groups were no significant difference compared with ALA, BSA and MBCD treatment groups. On the other hand, plasma and acrosomal membrane intact, and sperm motility in ALA+MBCD group were higher than single treatment groups (p<0.05), whereas ALA+BSA did not differ. Our findings indicate that carrier proteins such as BSA and MBCD could improve the effect of ALA during cryopreservation of boar sperm, and treatment of ALA with carrier proteins enhance membrane integrity, mitochondrial activity through reduction of ROS-induced LPO.

Evaluation of linolenic acid supplementation in extender for freezability and fertility of Murrah buffalo (Bubalus bubalis) bull semen

Linolenic acid is integral component of cell membrane that has the ability to protect the structural and functional integrity of buffalo spermatozoa during freeze-thawing. Therefore, present study was designed to evaluate supplementation of linolenic acid (0, 2.5, 5, 7.5 and 10.0 ng/ml) in extender on freezability and in vivo fertility of buffalo bull spermatozoa. Semen from healthy breeding Murrah buffalo bulls (4) was collected using artificial vagina (one ejaculate/bull/session; n=24). Qualified semen ejaculates (1–2 ml volume; >70% motility; ≥4 mass activity; 1.0 billion/ml concentration) were diluted with Tris-citric acid extender containing 0.0 (control), 2.5, 5.0, 7.5 and 10.0 ng/ml linolenic acid at 37°C and cryopreserved following established protocol. Sperm progressive motility, viability and plasma membrane integrity were recorded higher in extender containing 5.0 ng/ml of linolenic acid compared to control and other concentrations. Sperm acrosome and DNA integrity exhibited no difference in all experimental extenders with linolenic acid compared to control. Total 60 artificial inseminations were performed with the best evolved extender having linolenic acid (5.0 ng/ml) and control (30 inseminations each). In vivo fertility rates of buffalo semen were recorded higher with extender containing linolenic acid (5.0 ng/ml; 46.7%) compared to control (36.7%). In conclusion, supplementing 5.0 ng/ml linolenic acid in extender improved the postthaw quality and in vivo fertility of cryopreserved Murrah buffalo bull semen.

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.

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.

Expression and localization of aquaporins 3 and 7 in bull spermatozoa and their relevance to sperm motility after cryopreservation

Artificial insemination with cryopreserved semen is a well-developed technique commonly used for controlled reproduction in cattle. However, despite current technical advances, cryopreservation continues to damage bull spermatozoa, resulting in a loss of approximately 30 to 50% of viable spermatozoa post thawing. To further improve the efficiency of cryopreservation of bull spermatozoa, understanding the molecular mechanisms underlying the cryobiological properties that affect cryoinjuries during cryopreservation process of bull spermatozoa is required. In this study, we examined the expression and localization of aquaporin (AQP) 3 and AQP7 in fresh, cooled, and frozen-thawed bull spermatozoa. Furthermore, we investigated the relevance of AQP3 and AQP7 to motility and to membrane integrity in frozen-thawed bull spermatozoa. Western blotting against AQP3 and AQP7 in bull spermatozoa revealed bands with molecular weights of approximately 42 kDa and 53 kDa, respectively. In immunocytochemistry analyses, immunostaining of AQP3 was clearly observed in the principal piece of the sperm tail. Two immunostaining patterns were observed for AQP7 ―pattern 1: diffuse staining in head and entire tail, and pattern 2: diffuse staining in head and clear staining in mid-piece. Cooling and freeze-thawing did not affect the localization pattern of AQP7 and the relative abundances of AQP3 and AQP7 evaluated by Western blotting. Furthermore, we demonstrated that the relative abundances of AQP3 and AQP7 varied among ejaculates, and they were positively related to sperm motility, particularly sperm velocity, post freeze-thawing. Our findings suggest that AQP3 and AQP7 are possibly involved in the tolerance to freeze-thawing in bull spermatozoa, particularly in the sperm’s tail.

Óleo de peixe associado ao ácido ascórbico no diluidor para criopreservação de sêmen caprino

RESUMO O presente estudo teve como objetivo avaliar o efeito da inclusão de óleo de peixe associado ao ácido ascórbico no diluidor para criopreservação de sêmen caprino. Dois machos da raça Boer foram submetidos à coleta de sêmen pelo método de vagina artificial, sendo os ejaculados avaliados quanto aos aspectos físicos e morfológicos. Após avaliação, formou-se um pool, seguido do fracionamento em cinco grupos: G1 - diluidor citrato-gema e G2, G3, G4 e G5 - diluidor citrato-gema acrescido de 1,0; 2,0; 3,0 e 4,0% de óleo de peixe e 0,05% de ácido ascórbico, respectivamente. Após descongelamento, foram realizadas avaliações físicas do sêmen e os testes complementares de termorresistência lento (TTR), hiposmótico (HO), integridade acrossomal e compactação da cromatina espermática. Houve comportamento linear crescente (P<0,05) para motilidade pós-descongelamento. Não houve diferença (P>0,05) para vigor pós-descongelamento (2,00±0,24). No TTR não houve diferença (P>0,05) para motilidade e vigor espermáticos entre os tempos cinco e 180min, com médias inicial e final de 62,17±12,13 e 14,29±10,55 para motilidade e de 2,00±0,52 e 0,49±0,44 para vigor. Não houve diferença (P>0,05) para o HO, com porcentagem média de espermatozoides reativos de 23,5±5,96%. Houve comportamento linear crescente para acrossoma íntegro e decrescente para acrossoma irregular (P<0,05). Não houve diferença (P>0,05) na compactação da cromatina, com 97,06±1,17% de cromatina íntegra. A inclusão até 4% de óleo de peixe acrescido de ácido ascórbico no diluidor melhorou motilidade e integridade de acrossoma após a criopreservação.

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.

Effect of different concentrations of soybean lecithin and virgin coconut oil in Tris-based extender on the quality of chilled and frozen-thawed bull semen

AIM

The objective of this study was to evaluate the effects of different concentrations of soybean lecithin (SL) and virgin coconut oil (VCO) in Tris-based extender on chilled and frozen-thawed bull semen quality parameters.

MATERIALS AND METHODS

A total of 24 ejaculates were collected from four bulls via an electroejaculator. Semen samples were diluted with 2% VCO in Tris-based extender which consists of various concentrations of SL (1, 1.25, 1.5, and 1.75%). A 20% egg yolk in Tris used as a positive control (C+). The diluted semen samples were divided into two fractions; one for chilling which were stored at 4°C for 24, 72, and 144 h before evaluated for semen quality parameters. The second fraction used for freezing was chilled for 3 h at 4°C, packed into 0.25 mL straws and then cryopreserved in liquid nitrogen. The samples were then evaluated after 7 and 14 days. Chilled and frozen semen samples were thawed at 37°C and assessed for general motility using computer-assisted semen analysis, viability, acrosome integrity and morphology (eosin-nigrosin stain), membrane integrity, and lipid peroxidation using thiobarbituric acid reaction test.

RESULTS

The results showed that all the quality parameters assessed were significantly (p<0.05) improved at 1.5% SL concentration in chilled semen. Treatment groups of 1, 1.25, 1.5, and 1.75% SL were higher in quality parameters than the control group (C+) in chilled semen. However, all the quality parameters in frozen-thawed semen were significantly higher in the C+ than the treated groups.

CONCLUSION

In conclusion, supplementation of 1.5% SL in 2% VCO Tris-based extender enhanced the chilled bull semen. However, there was no marked improvement in the frozen-thawed quality parameters after treatment.

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.

Effects of an extension of the equilibration period up to 96 hours on the characteristics of cryopreserved bull semen

This study was designed to investigate the effects of an equilibration period up to 96 hours and three extenders (AndroMed, OPTIXcell, and Triladyl) on the quality of cryopreserved bull semen and to evaluate, whether an extension of the equilibration time to 72 hours does affect fertility in the field. One ejaculate of 17 bulls was collected and divided into three equal aliquots and diluted, respectively, with the three extenders. Each aliquot was again divided into five parts and equilibrated for 4, 24, 48, 72, and 96 hours before freezing in an automatic freezer. Sperm motility, plasma membrane and acrosome integrity (PMAI), and DNA fragmentation index (% DFI) were measured during equilibration. In addition to the parameters measured during equilibration, the percentage of viable sperm cells with high mitochondrial membrane potential (HMMP) was measured immediately after thawing, and after 3 hours of incubation at 37 °C. Sperm motility was assessed using CASA, and PMAI, HMMP, and % DFI were measured using flow cytometry. Equilibration time did affect all parameters before freezing (P < 0.01), and also the extender affected all parameters except HMMP (P < 0.05). After thawing, all parameters except HMMP immediately after thawing were influenced by the equilibration period (P < 0.001), whereas all parameters except % DFI immediately after thawing were influenced by the extender (P < 0.001). The changes of semen characteristics during 3 hours of incubation were also dependent on the equilibration time and the extender used in all parameters (P < 0.01). In the field study, semen of nine bulls was collected thrice weekly, processed using Triladyl egg yolk extender, and frozen in 0.25 mL straws with 15 × 10⁶ spermatozoa per straw. In total, the nonreturn rates on Day 90 after insemination (NRR90) of 263,816 inseminations in two periods were evaluated. Whereas semen collected on Mondays and Wednesdays was equilibrated for 24 hours in both periods, semen collected on Fridays was equilibrated for 4 hours in period one and equilibrated for 72 hours in period 2. No differences in NRR90 could be found (P > 0.05). In conclusion, extension of the equilibration time from 4 hours to 24-72 hours can improve motility and viability of cryopreserved semen after thawing. The extent of improvement in semen quality is dependent on the extender used. Prolongation of the equilibration period from 4 hours to 72 hours had no effect on fertility in the field.

Effect of docosahexanoic acid on quality of frozen–thawed bull semen in BioXcell extender

This study was conducted to investigate the effect of docosahexanoic acid (DHA) supplementation in BioXcell extender on the quality of frozen–thawed bull semen. Twenty-four ejaculates were collected from three bulls (eight from each bull). Ejaculates with motility ≥70% and normal morphology ≥80% were extended into BioXcell extender to which 0 (control), 3, 5, 10 or 15 ng mL–1 DHA was added. The supplemented semen samples were incubated at 37°C for 15 min for DHA uptake by spermatozoa. Later, samples were cooled for 2 h at 5°C and packaged into 0.25-mL straws, frozen in liquid nitrogen for 24 h and subsequently thawed for evaluation. Results are presented as percentages ± s.e.m. Supplementation with DHA at 3 ng mL–1 significantly improved sperm functional parameters including sperm motility, normal morphology, viability, acrosome integrity and membrane integrity when compared with other supplemented groups and the control. Lipid peroxidation increased as the incorporation of DHA supplementation increased. In conclusion, 3 ng mL–1 concentration of DHA resulted in superior quality of frozen–thawed bull spermatozoa and is suggested as the optimum level of DHA to be added into BioXcell extender.