Applications and interpretation of computer-assisted sperm analyses and sperm sorting methods in assisted breeding and comparative research

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.

Does Antioxidant Mitoquinone (MitoQ) Ameliorate Oxidative Stress in Frozen-Thawed Rooster Sperm?

In this study, we aimed to determine the benefit of mitoquinone (MitoQ) in rooster semen extenders on sperm quality, motility parameters, antioxidant capacities, and apoptotic changes in post-thawed rooster semen. A total of 85 ejaculates from 18 roosters were collected and then divided into five equal aliquots and cryopreserved in extenders with 1.0% soy lecithin nanoparticles that contained various concentrations of MitoQ (0 nM (M0), 50 nM (M50), 100 nM (M100), 150 nM (M150), and 200 nM (M200)). By using a computer-assisted semen analyzer, sperm motility parameters were assessed after freeze thawing. The M150 group had significantly higher percentages of total motility, progressive motility, viability, acrosome membrane integrity, and mitochondrial activity than the other groups (p < 0.05). Compared to other groups, M100 and M150 groups produced a higher percentage of plasma membrane integrity and ATP contents (p < 0.05). Additionally, the lowest levels of ROS and MDA in spermatozoa were observed in M150 group (p < 0.05), whereas the highest levels of ROS and MDA were observed in sperm in the controls or the M200 group (p < 0.05). Significantly higher values of SOD, GPx, and Cas-3 were found in the M150 group compared to other groups (p < 0.05). Overall, these results demonstrate that MitoQ at 150 nM not only ameliorates post-thawed sperm quality and motility parameters by restoring ATP levels and preventing membrane damage, but also improves redox balance and antiapoptotic activities.

Advances in sperm cryopreservation in farm animals: Cattle, horse, pig and sheep

Sperm cryopreservation is one of the most important procedures in the development of biotechnologies for assisted reproduction. In some farm animals, the use of cryopreserved sperm has so many benefits for which relevance has become more evident in recent decades. Values for post-thaw sperm quality, however, are variable among species and within individuals of the same species. There is no standardized methodology for each of the stages of the cryopreservation procedure (andrological examination, semen collection, dilution, centrifugation, resuspension of the pellet with the freezing medium, packaging, freezing and post-thaw sperm evaluation), which also contributes to differences among studies. Cryotolerance markers of sperm and seminal plasma (SP) have been evaluated for prediction of ejaculate freezability. In addition, in previous research, there has been a focus on supplementing cryopreservation media with different substances, such as enzymatic and non-enzymatic antioxidants. In most studies, inclusion of these substances have led to improved post-thaw sperm quality and fertilizing capacity as a result of minimizing the adverse effects on sperm structure and function. Another approach is the use of different cryoprotectants. The aim with this review article is to provide an update on sperm cryopreservation in farm animals. The main detrimental effects of cryopreservation are described, including the negative repercussion on reproductive performance. Furthermore, the potential use of molecular biomarkers to predict sperm cryotolerance is discussed, as well as the addition of substances that can mitigate the harmful impact of freezing and thawing on sperm.

Effect of Sperm Cryopreservation in Farm Animals Using Nanotechnology

Sperm cryopreservation is one of the sublime biotechnologies for assisted reproduction. In recent decades, there has been an increasing trend in the use of preserved semen. Post-thaw semen quality and values vary among animals of the same species. Similarly, there are species-specific variations in sperm morphology, i.e., sperm head, kinetic properties, plasma membrane integrity, and freezability. Similarly, the viability of sperm varies in the female reproductive tract, i.e., from a few hours (in cattle) to several days (in chicken). Various steps of sperm cryopreservation, i.e., male health examination, semen collection, dilution, semen centrifugation, pre- and post-thaw semen quality evaluation, lack standardized methodology, that result in differences in opinions. Assisted reproductive technologies (ART), including sperm preservation, are not applied to the same extent in commercial poultry species as in mammalian species for management and economic reasons. Sperm preservation requires a reduction in physiological metabolism by extending the viable duration of the gametes. Physiologically and morphologically, spermatozoa are unique in structure and function to deliver paternal DNA and activate oocytes after fertilization. Variations in semen and sperm composition account for better handling of semen, which can aid in improved fertility. This review aims to provide an update on sperm cryopreservation in farm animals.

Harnessing the value of reproductive hormones in cattle production with considerations to animal welfare and human health

The human population is ever increasing while the quality and quantity of natural resources used for livestock production decline. This calls for improved product efficiency and the development of improved and sustainable cattle production methods to produce higher quality products to satisfy the demands of both the modern and transient world. The goal of this review was to summarize the interactions, challenges, and opportunities in cattle production relating to their endocrine system, and how reproductive hormones and others impact economically important traits, animal welfare, and human health. A comprehensive literature search was conducted with a focus on analysis of natural hormones and the use of exogenous hormone administration for reproduction, growth, and development of beef and dairy cattle. Hormones regulate homeostasis and enhance important traits in cattle, including fertility, growth and development, health, and the production of both meat and milk products. Reproductive hormones such as testosterone, estradiol, progesterone, and related synthetics like trenbolone acetate and zeranol can be strategically utilized in both beef and dairy cattle production systems to enhance their most valuable traits, but the impact of these substances must account for the welfare of the animal as well as the health of the consumer. This scientific review provides a comprehensive analysis of the bovine endocrine system's impact on food animals and product quality which is vital for students, researchers, livestock producers, and consumers. Although important advances have been made in animal science and related technological fields, major gaps still exist in the knowledge base regarding the influence of hormones on the production and welfare of food animals as well as in the public perception of hormone use in food-producing animals. Filling these gaps through transformative and translational research will enhance both fundamental and applied animal science to feed a growing population.

Computer-assisted sperm analysis (CASA) in veterinary science: A review

Computer-assisted sperm analysis (CASA) allows an assessment of sperm motion and morphology more accurately and objectively than by subjective evaluation. Although, CASA instruments have improved significantly during last 40 years especially in terms of software, image capture and computer settings, little has changed regarding processes for analyzing sperm motion attributes. The main problem is related to validation, consistency and optimization of equipment and procedures. Differences among CASA systems denote problems of objective analysis of results between different semen processing units. If validated, CASA systems can provide a great tool to objectively compare sperm motility and morphology. Sperm motility is one of the indicators most evaluated before and after cryopreservation vis-à-vis quality and fertilizing ability. Researchers have determined a possible relationship of CASA outputs with bull fertility in vivo; however, a clear association has not yet been confirmed. Most CASA measures depend upon concentration, sample volume, type of extender, duration of analysis and thawing temperature. For each attribute, CASA software should provide outputs based on a range rather than means or medians for transformed data. The current review describes development, validation requirements, limitations and future expansions associated with CASA technology.

Sperm subpopulations influence the pregnancy rates in cattle

This study aimed to study the characteristics and subpopulations of spermatozoa from bulls with low and high reproductive performance based on pregnancy rates. Based on historical records of pregnancy rate from four farms, 24 bulls were selected. Two groups were established, with low pregnancy rates (n = 12; LOW), including bulls that presented pregnancy rates <52.27% (33.33% to 51.81%); and a group with high pregnancy rates (n = 12; HIGH), with pregnancy rates >52.27% (52.27% to 69.64%), after fixed-time artificial insemination (FTAI). The thawed sperm straws were analysed to sperm kinetics, morphology, plasma membrane integrity and sperm subpopulations. The LOW group exhibited a higher proportion of static cells (p < .05). In contrast, the HIGH group showed greater percentages for membrane integrity and total and progressive motility, and cells with fast and medium velocity (p < .05). In the cluster procedures, four sperm subpopulations were established. The low-fertility bulls presented the highest percentage of subpopulation 2 (41.46%), characterized by slow and progressive spermatozoa. The high-fertility bulls exhibited the highest percentage of subpopulation 3 (37.17%), characterized by fast and nonlinear spermatozoa. Results from this study indicated that bulls with greater percentages of fast and nonlinear spermatozoa seem to have greater fertilization capacity and the subpopulations analysis can be considered a tool to identify ejaculates with high fertility.

Sperm motility, kinematics, morphometry and morphology over two seasons in free-ranging African elephants (Loxodonta africana)

This study aimed to address the lack of information on quantitative semen and sperm characteristics of free-ranging African elephants. Nineteen ejaculates were collected from 12 elephant bulls by means of electroejaculation in spring (Season 1, end of dry season, n=7) and in autumn (Season 2, end of rainy season, n=12). While most elephant cows are in oestrus in the rainy season, it is not evident whether sperm quality also improves during this period. Semen samples were assessed using computer-aided sperm analysis (CASA), brightfield microscopy and transmission electron microscopy. Seasonal differences and individual variation in sperm quality of bulls were apparent, with ejaculates collected during Season 2 revealing higher percentages for total motility, progressive motility, rapid-swimming spermatozoa and kinematic parameters compared with Season 1 (P<0.05). Although normal sperm morphology percentage was similar over the two seasons, more sperm tail defects were found in Season 2 (P<0.05). The baseline reference data and multivariate sperm parameter associations reported in this study can be used to predict elephant bull sperm quality and potential to fertilise. It is clear that CASA can detect subtle differences in sperm quality of African elephant ejaculates and should be the approach for future investigations.

Assessing coral sperm motility

The declining reproductive viability of corals threatens their ability to adapt to changing ocean conditions. It is vital that we monitor this viability quantitatively and comparatively. Computer-assisted sperm analysis (CASA) systems offer in-depth analysis used regularly for domestic and wildlife species, but not yet for coral. This study proposes quality control procedures and CASA settings that are effective for coral sperm analysis. To resolve disparities between CASA measurements and evaluations by eye, two negative effects on motility had to be resolved, slide adhesion (procedural) and sperm dilution (biological). We showed that the addition of bovine serum albumin, or caffeine, or both to fresh sperm reduced adhesion in the CASA cassettes, improved motility and motile sperm concentration (P < 0.0001), yet these additions did not affect measurements of total sperm concentration. Diluting coral sperm reduced sperm motility (P = 0.039), especially from heat-stressed corals. We found CASA concentration counts comparable to haemocytometer and flow cytometer measures (P = 0.54). We also found that motile sperm per egg is a useful predictor of fertilisation success, using cryopreserved sperm. Standard measurements of coral reproductive characteristics inform our understanding of the impacts of climate change on reef populations; this study provides a benchmark to begin this comparative work.

Effect of oviductal fluid on bull sperm functionality and fertility under non-capacitating and capacitating incubation conditions

This study investigated the effect of bovine oviductal fluid from late follicular (LF) and early luteal (EL) phases on bull sperm functionality under non-capacitating (NCAP) and capacitating (CAP) conditions. Frozen-thawed semen samples from five bulls were thawed and incubated (0, 1 or 2 h) in NCAP and CAP media supplemented with 1% bovine oviductal fluid (LF and EL groups) and in absence of fluid (C group). Motion parameters were assessed by CASA; sperm viability, acrosomal integrity and membrane lipid disorder parameters were evaluated by flow cytometry; and sperm DNA fragmentation was evaluated by the Comet assay. Finally, in vitro fertilization with sperm treated under CAP conditions was performed and further embryo culture results evaluated. In NCAP medium, addition of LF and EL fluid increased the total and progressive motility, and LF fluid improved the stability of sperm DNA. However, under CAP conditions addition of LF and EL fluid decreased some sperm motion parameters and some parameters of sperm DNA stability. Proportion of viable sperm cells with low lipid disorder was higher in NCAP than CAP medium and addition of LF fluid markedly increased the proportion of viable spermatozoa with high lipid disorder and acrosome alteration (spontaneous acrosome reaction). Under current conditions, incubation of bull sperm with oviductal fluid before insemination did not affect detrimentally the IVF results nor embryo development, being blastocyst rate similar between CAP-LF, CAP-EL and control groups. In conclusion, oviductal fluid positively influences sperm functionality and modulate in vitro capacitation.

Melatonin reduces cAMP-stimulated capacitation of ram spermatozoa

The presence of melatonin receptors on the surface of ram spermatozoa has led to speculation about melatonin having a role in sperm functionality. The aim of this study was to elucidate the mechanism through which melatonin regulates ram sperm capacitation induced by a cocktail containing cAMP-elevating agents. Cocktail samples capacitated in the presence of 1µM melatonin showed lower percentages of capacitated spermatozoa (chlortetracycline staining; P<0.001) together with a decrease in protein tyrosine phosphorylation (P<0.01) and lower levels of reactive oxygen species (ROS) and cAMP (P<0.05) compared with cocktail samples without the hormone. Determination of kinematic parameters, together with principal component and cluster analyses, allowed us to define four sperm subpopulations (SP). After 3h of incubation with cAMP-elevating agents, the percentages of spermatozoa belonging to SP1 (high straightness) and SP4 (less-vigorous spermatozoa with non-linear motility) increased while SP2 and SP3 (rapid spermatozoa starting hyperactivation or already hyperactivated) decreased compared with the control sample. The presence of melatonin at 100 pM and 10nM restored these subpopulations to values closer to those found in the control sample. These results indicate that melatonin at micromolar concentrations modulates ram sperm capacitation induced by cAMP-elevating agents, reducing ROS and cAMP levels, whereas at lower concentrations melatonin modifies motile sperm subpopulations. These findings warrant further studies on the potential use of melatonin for controlling capacitation in artificial insemination procedures.

Ejaculated compared with epididymal stallion sperm vitrification

The aim of this study was to evaluate the effect of trehalose and lactose extenders on ejaculated and epididymal stallion sperm vitrification. Ejaculated semen samples were collected from seven fertile stallions, and cauda epididymis samples were collected from ten stallion carcasses after slaughter. Both the ejaculated and the epididymis samples were diluted and vitrified using INRA 96® and bovine serum albumin as well as trehalose or lactose. As a control, ejaculated and epididymal samples were collected and frozen using the conventional method. Vitrification was performed by immersing sperm suspensions directly in LN2. After thawing or devitrification, there was assessment of samples for sperm motility using computer-assisted analysis. Viability was assessed using SYBR-14 and propidium iodide (PI) and acrosome integrity by fluorescein using isothiocyanate combined with peanut agglutinin (FITC-PNA) and PI. Epididymal sperm vitrification with trehalose (EPT) or lactose (EPL) resulted in greater progressive sperm motility than sperm of the control sample (EPC). After post-thaw/devitrification of sperm in the EPT group, sperm motility was greater (P<0.001) compared to that using EPL (50.72 ± 5.09% compared with 34.21 ± 3.02%). The results from assessment of ejaculated sperm samples after undergoing the vitrification process indicated cells were less viable (P<0.001) than the control (EJC) sample. In conclusion, vitrification of epididymal stallion sperm using trehalose might be a beneficial alternative for the long-term storage of sperm samples with great economic value. Spermatozoa from vitrified ejaculates of stallions, however, had lesser motility and viability rates than samples subjected to conventional freezing.

CASA-Mot in mammals: an update

Sperm motility is one of the most widely used parameters of sperm quality. Computer-aided sperm motility analysis (CASA-Mot) systems were developed to reduce the subjectivity of sperm motility assessment, and have had broad scientific and practical acceptance. In this review, the sources of variation and current applications of this technology and its relationships with other sperm quality tests are described in detail. Despite remarkable advances in the technique, there is still great need for standardisation in many species, and the numerous factors that affect the results make it difficult to provide universally accepted criteria for classifying semen samples based on sperm motility characteristics. The main fields for CASA-Mot include the study of male fertility and pathologies, evaluation of the effects of physical and chemical agents, improvement of epidemiological survey studies, more precise calculation of seminal doses for farm animals, realisation of basic studies about sperm function, improvement of sperm technologies such as cryopreservation and quality control analysis. Numerous relationships have been established between CASA-Mot and other sperm quality tests, although most of these parameters are complementary. Future CASA-Mot systems will probably be able to integrate several sperm quality parameters with motility.

Current perspectives of CASA applications in diverse mammalian spermatozoa

Since the advent of computer-aided sperm analysis (CASA) some four decades ago, advances in computer technology and software algorithms have helped establish it as a research and diagnostic instrument for the analysis of spermatozoa. Despite mammalian spermatozoa being the most diverse cell type known, CASA is a great tool that has the capacity to provide rapid, reliable and objective quantitative assessment of sperm quality. This paper provides contemporary research findings illustrating the scientific and commercial applications of CASA and its ability to evaluate diverse mammalian spermatozoa (human, primates, rodents, domestic mammals, wildlife species) at both structural and functional levels. The potential of CASA to quantitatively measure essential aspects related to sperm subpopulations, hyperactivation, morphology and morphometry is also demonstrated. Furthermore, applications of CASA are provided for improved mammalian sperm quality assessment, evaluation of sperm functionality and the effect of different chemical substances or pathologies on sperm fertilising ability. It is clear that CASA has evolved significantly and is currently superior to many manual techniques in the research and clinical setting.

Assessment and preservation of liquid and frozen-thawed Black crested mangabey (Lophocebus aterrimus) spermatozoa obtained by transrectal ultrasonic-guided massage of the accessory sex glands and electroejaculation

The Black Crested Mangabey (Lophocebus aterrimus) is an African monkey listed as Near Threatened by the IUCN and in captivity the population is limited to 34 males. The aim of this study was to evaluate two Black Crested Mangabey males, maintained in captivity in a zoological garden and suspected of infertility, with a complete examination of their genital tract using ultrasonography, followed by recovery of semen using transrectal ultrasonic massage of the accessory sexual glands (TUMASG) and electroejaculation. One male had small testicular and accessory sex gland sizes indicative of senile hypoplasia. The other male was suspected of infertility. Four semen samples were obtained. Fresh semen was initially evaluated, diluted in Refrigeration Medium Test Yolk buffer, cooled at 15 °C and cryopreserved. Endocrine profiles (testosterone, oestradiol, FSH, LH, cortisol), prostatic specific antigen and semen variables (volume, concentration, motility by CASA, viability and acrosome status using flow cytometry, morphology, morphometry utilising TEM) were evaluated in raw, cooled and cryopreserved samples. There was no detrimental effect of cooling or cryopreservation on sperm viability and acrosomal integrity. Similar percentages of viable and acrosome-intact spermatozoa were present in cooled (for 6 h) and frozen-thawed semen samples (75.1% compared with 69.0%, P > 0.05), while progressive motility was greater in cooled, compared with frozen-thawed samples (81.5% compared with 67.3%). This study was the first in which there was evaluation of sperm variables in this species and, although this study is limited by the number of animals it provides background information for further studies using assisted reproductive technologies.

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.

Combined effects of type and depth of counting chamber, and rate of image frame capture, on bull sperm motility and kinematics

Semen quality assessment requires accurate, reliable and objective methods for examination of sperm variables including sperm motility. For preparation of semen samples for artificial insemination, as a genetic resource, samples that are used for insemination need to have the capacity to result in a highly acceptable fertility rate. Several methods have been developed for evaluation of bull sperm in laboratory conditions and for preparation of doses for artificial insemination. Computer-assisted semen analyses can provide objective information on various sperm variables. Nevertheless, this equipment requires fine-calibrations considering differences among species, breeds and conditions for sample evaluation and data analyses. In the present study, there was examination of the interaction between factors such as image frame rate and type and depth of counting chamber in which sperm were evaluated, together with differences between bulls of four breeds. The use of the Spermtrack® reusable 10 μm-depth chamber provided more reliable results than results obtained using disposable chambers (10 and 20 μm depth). A capture rate of at least 90 fps is required for assessment of sperm motility percentage, whereas a rate of 250 fps is needed for obtaining consistent kinematic data. Differences among breeds in the present study indicate conditions for sperm analyses should include specific equipment calibrations for each breed. These results contribute to development of more precise conditions for assessments of bull sperm quality taking into account breed differences and the requirement each breed has for the adequate evaluation and preparation of samples for artificial insemination.

Implications of boar sperm kinematics and rheotaxis for fertility after preservation

Artificial insemination (AI) is the single most important assisted reproductive technique devised to facilitate the genetic improvement of livestock. In the swine industry, it has broadly replaced natural service over the last number of decades which has been made possible by the high pregnancy rates and litter sizes obtainable with semen extended, up to, and sometimes beyond 5 d. Central to achieving good reproductive performance is the ability of boar studs to monitor semen quality, the basis of which has long been the assessment of sperm motility by subjective and, more recently, by more objective computerised systems. In this review, the literature on the relationship between sperm motility and kinematic parameters and field fertility is summarised. We discuss how this relationship is dependent on factors such as the viscosity of the media and the use of standard operating procedures. Emerging evidence is discussed regarding the importance of sperm rheotaxis and thigmotaxis as long-distance sperm guidance mechanisms, which enable motile functional spermatozoa to avoid the backflow of fluid, mucus and semen from the sow's uterus in the hours post AI, facilitating the establishment of sperm reservoirs in the oviducts. The literature on the use of microfluidics in studying sperm rheotaxis in vitro is also summarised, and we discuss how these systems, when combined with techniques such as lensless microscopy, have the potential to offer more physiological assessments of the swimming patterns of boar spermatozoa. Finally, possible future avenues of further investigation are proposed.

Sperm motility and lipid composition in internally fertilizing ocellate river stingray Potamotrygon motoro

All extant groups of Elasmobranches have internal fertilization and the structure of the male reproductive organs is very specific: sperm passes from the internal organs via the cloaca, but the male copulating organ (clasper) is distant from the cloaca. This suggests that sperm can contact the surrounding medium before fertilization. Because of this involvement with the environment, external signaling in sperm motility activation could occur in these species even though their fertilization mode is internal. In this case, spermatozoa of Elasmobranches should hypothetically possess a specific structure and membrane lipid composition which supports physiological functions of the sperm associated with environmental tonicity changes occurring at fertilization. Additionally, sperm motility properties in these taxa are poorly understood. The current study examined sperm lipid composition and motility under different environmental conditions for the ocellate river stingray, Potamotrygon motoro, an endemic South America freshwater species. Sperm samples were collected from six mature males during the natural spawning period. Sperm motility was examined in seminal fluid and fresh water by light video microscopy. Helical flagellar motion was observed in seminal fluid and resulted in spermatozoon progression; however, when diluted in fresh water, spermatozoa were immotile and had compromised structure. Lipid class and fatty acid (FA) composition of spermatozoa was analyzed by thin layer and gas chromatography. Spermatozoa FAs consisted of 33 ± 1% saturated FAs, 28 ± 1% monounsaturated FAs (MUFAs), and 41 ± 1% polyunsaturated FAs (PUFAs), and a high content of n-6 FAs (32 ± 2%) was measured. These results allowed us to conclude that sperm transfer from P. motoro male into female should occur without coming into contact with the hypotonic environment so as to preserve potent motility. In addition, this unusual reproductive strategy is associated with specific spermatozoa structure and lipid composition. Low level of docosahexaenoic acid and relatively low PUFA/MUFA ratio probably account for the relatively low fluidity of freshwater stingray membrane and can be the main reason for its low tolerance to hypotonicity.

Effect of Mare Colostrum in Extenders for Freezing Stallion Semen

This study aimed to evaluate the addition of mare colostrum in stallion freezing extenders to improve sperm quality. First, colostrum samples were collected from four mares after the foal's birth and their composition was determined. Ejaculates were collected from nine fertile stallions. Sperm samples were pooled, diluted, and cryopreserved into three experimental extender groups: Lactose-based extender supplemented with mare colostrum (20%), lactose-based extender supplemented with egg yolk (20%), and BotuCrio. The quality of the post-thaw semen samples were evaluated assessing sperm motility by means of computer-assisted analysis, viability by SYBR-14 and propidium iodine (PI) stain, acrosome integrity by fluorescein isothiocyanate and peanut agglutinine (FITC-PNA) and PI stain, plasma membrane functionality by hypo-osmotic swelling (HOS) test, and DNA denaturation by acridine orange (AO) test. There were no significant differences in the percentages of total motility, acrosome integrity, and DNA fragmentation among the extenders after thawing. Kinematics parameters showed significantly higher values in BotuCrio than in lactose extenders (P < .05). BotuCrio and lactose colostrum extender yielded significantly better rates for HOS-test, linearity, straightness, and wobble than egg-yolk extender (P < .05). However, in relation to sperm viability, lactose egg yolk extender showed significantly better results in comparison to the others seminal experimental media (P < .05). In conclusion, the incorporation of mare colostrum into cryopreservation media protected the sperm against cold-shock; therefore, it may be a good cryoprotectant agent alternative in extenders for freezing stallion semen.

High-throughput flowing upstream sperm sorting in a retarding flow field for human semen analysis

In this paper, we propose a microfluidic device capable of generating a retarding flow field for the sorting and separation of human motile sperm in a high-throughput manner. The proposed sorting/separation process begins with a rapid flow field in a straight-flow zone to carry sperm into a sorting zone to maintain the sperm's mobility. The sorting zone consists of a diffuser-type sperm sorter to differentiate sperm with different motilities based on the flowing upstream nature of human sperm in a retarding flow field. The dead sperm will then be separated from the live ones by passing through a dumbbell flow field to the outlet for disposal. The proposed flowing upstream sperm sorter (FUSS) is designed to imitate the selection mechanism found in the female body when sperm swim into the uterus. The experimental results demonstrate the utility of this device with regard to throughput (approximately 200 000 sperm per minute and a maximum of 200 million cells per mL), efficiency (90% of selected sperm are mobile), and the ability to select sperm with high motility (∼20% of sperm with a velocity exceeding 120 μm s^-1). The proposed device is suitable for intrauterine insemination as well as in vitro fertilization thanks to the highly efficient sorting process not interfering with the natural function and energy resource of human sperm.

Fish Sperm Assessment Using Software and Cooling Devices

For gamete quality evaluation, there are innovative, rapid, and quantitative techniques that can provide useful data for aquaculture. Computerized systems for sperm analysis were developed to measure several parameters and one of the most commonly measured is the sperm motility. Initially, this computer technology was designed for mammalian species, although it can also be used for fish sperm analysis. Fish have specific features that can affect sperm assessment such as a short motility time after activation and, in some cases, adaptation to lower temperatures. Thus, it is necessary to modify both software and hardware components to make motility analysis more efficient for fish sperm analysis. For mammalian sperm, the heating plate is used to maintain optimal temperatures of spermatozoa. However, for some fish species, it is advantageous to use a lower temperature to prolong the duration of motility, since the sperm remain active for less than 2 min. Therefore, cooling devices are necessary to refrigerate samples at constant temperature over the time of analysis, including on the optical microscope. This protocol describes the analysis of fish sperm motility using software for sperm analysis and new cooling devices to optimize the results.

Bottlenose dolphin (Tursiops truncatus) sperm revisited: Motility, morphology and ultrastructure of fresh sperm of consecutive ejaculates

Computer aided sperm analysis systems allow detailed examination of sperm motility and morphology variables, which are important for the understanding of the spermatology of a species and the development of assisted reproductive techniques. Cetacean biology is too complex to study in the wild and data from captive individuals provide an important alternative for the conservation of these charismatic animals. The present study evaluates ejaculate and sperm characteristics, including sperm motility, kinematic variables and quantitative sperm morphology and ultrastructure, of consecutive ejaculates from Atlantic bottlenose dolphins (Tursiops truncatus). Sperm concentrations and total and progressive motilities were greater in the second than the first ejaculate, with all ejaculates being of very high quality (6.9-1127 × 10⁶/ml sperm concentration, 75% to 91% total motility and 89% to 96% normal sperm). Most sperm in an ejaculate (≥84%) were highly (VCL>150 μm/s) and progressively motile with very few abnormal sperm. The sperm have small heads, a short but very bulky midpiece and a long tail. Detailed sperm morphometrics using CASA indicated there were similarities from one ejaculate to the next. The large mitochondria with extensive cristae mitochondriales are tightly packed in the midpiece resulting in a large midpiece volume. All the semen and sperm characteristics indicate high quality sperm and support the assumption that a multimale mating system is present in T. truncatus.

CASA-Mot technology: how results are affected by the frame rate and counting chamber

For over 30 years, CASA-Mot technology has been used for kinematic analysis of sperm motility in different mammalian species, but insufficient attention has been paid to the technical limitations of commercial computer-aided sperm analysis (CASA) systems. Counting chamber type and frame rate are two of the most important aspects to be taken into account. Counting chambers can be disposable or reusable, with different depths. In human semen analysis, reusable chambers with a depth of 10µm are the most frequently used, whereas for most farm animal species it is more common to use disposable chambers with a depth of 20µm . The frame rate was previously limited by the hardware, although changes in the number of images collected could lead to significant variations in some kinematic parameters, mainly in curvilinear velocity (VCL). A frame rate of 60 frames s-1 is widely considered to be the minimum necessary for satisfactory results. However, the frame rate is species specific and must be defined in each experimental condition. In conclusion, we show that the optimal combination of frame rate and counting chamber type and depth should be defined for each species and experimental condition in order to obtain reliable results.

Physical and kinematic properties of cryopreserved camel sperm after elimination of semen viscosity by different techniques

This investigation aimed to determine the influence of using different techniques for liquefaction of semen on post-thaw physical and dynamic characteristics of camel spermatozoa. A total of 144 ejaculates were collected from 3 adult camels, Camelus dromedarius, twice-weekly over 3 consecutive breeding seasons. A raw aliquot of each ejaculate was evaluated for physical and morphological properties, whereas the remaining portion was diluted (1:3) with glycerolated Tris lactose egg yolk extender, and was further subjected to one of the following liquefaction treatments: control (untreated), 5μl/ml α-amylase, 0.1mg/ml papain, 5u/ml bromelain, or 40-kHz nominal ultrasound frequency. The post-thaw objective assessment of cryopreserved spermatozoa, in all groups, was performed by a computer-assisted sperm analysis (CASA) system. The results revealed that all liquefaction treatments improved (P<0.05) post-thaw motility, viability and sperm motion criteria. However, an adverse effect (P<0.05) was observed in acrosome integrity, sperm cell membrane integrity and percent of normal sperm in all enzymatically-treated specimens compared to both control and ultrasound-treated semen. These results elucidate the efficiency of utilizing ultrasound technology for viscosity elimination of camel semen. In addition, developing enzymatic semen liquefaction techniques is imperious to benefit from when applying assisted reproductive technologies, particularly AI and IVF, in camels.

Effect of sexual steroids on boar kinematic sperm subpopulations

Here, we show the effects of sexual steroids, progesterone, testosterone, or estradiol on motility parameters of boar sperm. Sixteen commercial seminal doses, four each of four adult boars, were analyzed using computer assisted sperm analysis (CASA). Mean values of motility parameters were analyzed by bivariate and multivariate statistics. Principal component analysis (PCA), followed by hierarchical clustering, was applied on data of motility parameters, provided automatically as intervals by the CASA system. Effects of sexual steroids were described in the kinematic subpopulations identified from multivariate statistics. Mean values of motility parameters were not significantly changed after addition of sexual steroids. Multivariate graphics showed that sperm subpopulations were not sensitive to the addition of either testosterone or estradiol, but sperm subpopulations responsive to progesterone were found. Distribution of motility parameters were wide in controls but sharpened at distinct concentrations of progesterone. We conclude that kinematic sperm subpopulations responsive to progesterone are present in boar semen, and these subpopulations are masked in evaluations of mean values of motility parameters. © 2017 International Society for Advancement of Cytometry.

Incubation of boar spermatozoa in viscous media by addition of methylcellulose improves sperm quality and penetration rates during in vitro fertilization

This work was designed to study whether viscous media can improve the in vitro sperm functionality in pigs by using methylcellulose as a thickener. Viscosity of porcine oviductal fluid (POF) was compared with culture medium (Tyrode's) supplemented with methylcellulose (MET 0, 0.5 and 1% w/v). Spermatozoa were incubated in the different media (0, 1 and 2 h) and sperm motion parameters, lipid membrane disorder, plasma membrane integrity and reactive oxygen species (ROS) formation were assessed. Fertilization results were assessed i) preincubating spermatozoa in the viscous media followed by gamete coculture in a non-viscous medium; and ii) gamete coculture in the viscous media. Viscosity of POF from early luteal phase was higher than late follicular phase. Medium without methylcellulose presented constant viscosity with increased shear rate, while viscosity of the POF and media with methylcellulose was reduced by increased shear rates. Methylcellulose improved sperm linearity, straightness and the proportion of fast-linear spermatozoa. Moreover, methylcellulose increased the rate of viable spermatozoa with intact acrosome and low lipid disorder, reducing the ROS generation. Preincubation in viscous media increased the penetration rate and the mean number of spermatozoa bound to the zona pellucida (both with 0.5 and 1% MET) and reduced monospermy with 1% MET. On the other hand fertilization in the viscous media reduced penetration rate and increased monospermy. The efficiency of the IVF system was not improved with the use of viscous media. The results show the relevance of increasing viscosity thus making the in vitro media more comparable to physiological conditions.

Cryoprotection synergism between glycerol and dimethyl sulfoxide improves the mitochondrial transmembrane potential, plasmalemma, acrosomal and DNA integrities, and in vivo fertility of water buffalo (Bubalus bubalis) spermatozoa

The objective of the study was to devise a cryoprotection synergism between glycerol and dimethyl sulfoxide (DMSO) for water buffalo spermatozoa. Additionally, the effect of best evolved concentrations of glycerol and DMSO in extender was assessed on in vivo fertility of buffalo spermatozoa. Ejaculates (n = 30) were equally distributed into five aliquots; first aliquot was diluted at 37 °C in extender having 7 % glycerol (control); second aliquot was diluted at 37 °C as well as at 4 °C in extender having 3.5 % DMSO (Group 1); third aliquot was diluted at 37 °C in extender having 3.5 % glycerol and then at 4 °C in extender having 3.5 % DMSO (Group 2); fourth aliquot was diluted at 37 °C in extender having 3.5 % DMSO and then at 4 °C in extender having 3.5 % glycerol (Group 3); fifth aliquot was diluted in extenders having 1.75 % glycerol and 1.75 % DMSO at 37 as well as at 4 °C (Group 4). At post thawing, sperm progressive motility (%), rapid velocity (%), average path velocity (µm/s), curved line velocity (µm/s), in vitro longevity (%), structural and functional integrity of plasmalemma (%), mitochondrial transmembrane potential (%) and viable sperm with intact acrosome (%) were higher (P < 0.05) in Group 4 compared to other treatment groups and control. Regarding sperm DNA integrity (%); it was higher (P < 0.05) in Group 4 compared to Group 1, 3 and control. The in vivo fertility (%) of buffalo spermatozoa was significantly higher with Group 4 compared to control (69.45 vs. 59.81). In conclusion, synergism exists between glycerol and DMSO (Group 4) in improving the quality and in vivo fertility of cryopreserved water buffalo spermatozoa.

Environmental chemicals impact dog semen quality in vitro and may be associated with a temporal decline in sperm motility and increased cryptorchidism

Adverse temporal trends in human semen quality and cryptorchidism in infants have been associated with exposure to environmental chemicals (ECs) during development. Here we report that a population of breeding dogs exhibit a 26 year (1988-2014) decline in sperm quality and a concurrent increased incidence of cryptorchidism in male offspring (1995-2014). A decline in the number of males born relative to the number of females was also observed. ECs, including diethylhexyl phthalate (DEHP) and polychlorinated biphenyl 153 (PCB153), were detected in adult dog testes and commercial dog foods at concentrations reported to perturb reproductive function in other species. Testicular concentrations of DEHP and PCB153 perturbed sperm viability, motility and DNA integrity in vitro but did not affect LH stimulated testosterone secretion from adult testis explants. The direct effects of chemicals on sperm may therefore contribute to the decline in canine semen quality that parallels that reported in the human.

Assessment of semen quality in pure and crossbred Jersey bulls

AIM

To compare the seminal attributes of neat, pre-freeze (at equilibration), and post-freeze (24 h after freezing) semen in pure and crossbred Jersey bulls.

MATERIALS AND METHODS

Total 36 ejaculates (3 ejaculates from each bull) were collected from 6 pure Jersey and 6 crossbred Jersey bulls and evaluated for various seminal attributes during neat, pre-freeze, and post-freeze semen.

RESULTS

The mean (±standard error [SE]) values of neat semen characteristics in pure and crossbred Jersey bulls were recorded such as volume (ml), color, consistency, mass activity (scale: 0-5), and sperm concentration (millions/ml). The extended semen was further investigated at pre-freeze and post-freeze stages and the mean (±SE) values recorded at neat, pre-freeze, and post-freeze semen were compared between pure and crossbred Jersey bulls; sperm motility (80.55±1.70%, 62.77±1.35%, 46.11±1.43% vs. 80.00±1.80%, 65.00±1.66%, 47.22±1.08%), live sperm count (83.63±1.08%, 71.72±1.09%, 58.67±1.02% vs. 80.00±1.08%, 67.91±1.20%, 51.63±0.97%), total abnormal sperm count (8.38±0.32%, 12.30±0.39%, 16.75±0.42% vs. 9.00±0.45%, 12.19±0.48%, 18.11±0.64%), hypo-osmotic swelling (HOS) reacted spermatozoa (71.88±0.77%, 62.05±0.80%, 47.27±1.05% vs. 72.77±1.02%, 62.11±0.89%, 45.94±1.33%), acrosome integrity (89.05±0.83%, 81.33±0.71%, 71.94±0.86% vs. 86.55±0.57%, 78.66±0.42%, 69.38±0.53%), and DNA integrity (99.88±0.07%, 100, 99.66±0.11% vs. 99.94±0.05%, 100, 99.44±0.18%,). The volume, color, consistency, sperm concentration, and initial motility in pure and crossbred Jersey bulls did not differ significantly (p>0.05). The mass activity was significantly (p<0.05) higher in pure Jersey as compare to crossbred Jersey bulls. Live sperm percentage and acrosome integrity was significantly (p<0.01) higher in pure Jersey bulls as compared to crossbred Jersey bulls. However, no statistical difference (p>0.05) was observed in abnormal sperm; HOS reacted spermatozoa and DNA integrity percentage among breeds.

CONCLUSION

It may be concluded that the quality of pure Jersey bull semen was comparatively better than the crossbred Jersey bulls.

Glyph-Based Video Visualization for Semen Analysis

The existing efforts in computer assisted semen analysis have been focused on high speed imaging and automated image analysis of sperm motility. This results in a large amount of data, and it is extremely challenging for both clinical scientists and researchers to interpret, compare and correlate the multidimensional and time-varying measurements captured from video data. In this work, we use glyphs to encode a collection of numerical measurements taken at a regular interval and to summarize spatio-temporal motion characteristics using static visual representations. The design of the glyphs addresses the needs for (a) encoding some 20 variables using separable visual channels, (b) supporting scientific observation of the interrelationships between different measurements and comparison between different sperm cells and their flagella, and (c) facilitating the learning of the encoding scheme by making use of appropriate visual abstractions and metaphors. As a case study, we focus this work on video visualization for computer-aided semen analysis, which has a broad impact on both biological sciences and medical healthcare. We demonstrate that glyph-based visualization can serve as a means of external memorization of video data as well as an overview of a large set of spatiotemporal measurements. It enables domain scientists to make scientific observation in a cost-effective manner by reducing the burden of viewing videos repeatedly, while providing them with a new visual representation for conveying semen statistics.

Subpopulation pattern of eel spermatozoa is affected by post-activation time, hormonal treatment and the thermal regimen

There has been a marked reduction in natural stocks of eels (genus Anguilla) over the past 60 years, and the culture of eels is still based on the capture of very large quantities of juveniles. It is necessary to close the life cycle in captivity in order to ease the pressure on wild populations. The aims of the present study were to evaluate sperm subpopulations (through cluster analysis of computer-aided sperm analysis data) in the European eel (Anguilla anguilla) and to assess the effects of motility acquisition time after activation (i.e. at 30, 60 and 90 s), the thermal regimen (i.e. 10°C (T10) or 15°C (T15) and up to 20°C, or constant at 20°C (T20)) and hormonal treatments (i.e. human chorionic gonadotropin (hCG), recombinant (r) hCG or pregnant mare serum gonadotropin (PMSG)) on these subpopulations. In all cases, we obtained three subpopulations of spermatozoa: low velocity and linear (S1); high velocity with low linearity (S2); and high velocity and linear (S3; considered high quality). Total motility and S1 were affected by acquisition time; thus, 30 s is recommended as the standard time for motility acquisition. When eels were kept at 20°C (T20), motility data fitted quadratic models, with the highest motility and proportion of S3 between Weeks 8 and 12 after the first injection. Lower temperatures (T10, T15) delayed spermiation and the obtaining of high-quality spermatozoa (S3), but did not seem to alter the spermiation process (similar subpopulation pattern). Conversely, the hormonal treatments altered both the dynamics of the subpopulation pattern and the onset of spermiation (with PMSG delaying it). Total motility and the yield of S3 with the widely used hCG treatment varied throughout the spermiation period. However, using rhCG allowed us to obtain high-quality and constant motility for most of the study (Weeks 7–20), and the S3 yield was also higher overall (61.8 ± 1.3%; mean ± s.e.m.) and more stable over time than the other hormonal treatments (averaging 53.0 ± 1.4%). Using T20 and rhCG would be more economical and practical, allowing us to obtain a higher number of S3 spermatozoa over an extended time.

Computer-assisted sperm analysis (CASA): capabilities and potential developments

Computer-assisted sperm analysis (CASA) systems have evolved over approximately 40 years, through advances in devices to capture the image from a microscope, huge increases in computational power concurrent with amazing reduction in size of computers, new computer languages, and updated/expanded software algorithms. Remarkably, basic concepts for identifying sperm and their motion patterns are little changed. Older and slower systems remain in use. Most major spermatology laboratories and semen processing facilities have a CASA system, but the extent of reliance thereon ranges widely. This review describes capabilities and limitations of present CASA technology used with boar, bull, and stallion sperm, followed by possible future developments. Each marketed system is different. Modern CASA systems can automatically view multiple fields in a shallow specimen chamber to capture strobe-like images of 500 to >2000 sperm, at 50 or 60 frames per second, in clear or complex extenders, and in <2 minutes, store information for ≥ 30 frames and provide summary data for each spermatozoon and the population. A few systems evaluate sperm morphology concurrent with motion. CASA cannot accurately predict 'fertility' that will be obtained with a semen sample or subject. However, when carefully validated, current CASA systems provide information important for quality assurance of semen planned for marketing, and for the understanding of the diversity of sperm responses to changes in the microenvironment in research. The four take-home messages from this review are: (1) animal species, extender or medium, specimen chamber, intensity of illumination, imaging hardware and software, instrument settings, technician, etc., all affect accuracy and precision of output values; (2) semen production facilities probably do not need a substantially different CASA system whereas biology laboratories would benefit from systems capable of imaging and tracking sperm in deep chambers for a flexible period of time; (3) software should enable grouping of individual sperm based on one or more attributes so outputs reflect subpopulations or clusters of similar sperm with unique properties; means or medians for the total population are insufficient; and (4) a field-use, portable CASA system for measuring one motion and two or three morphology attributes of individual sperm is needed for field theriogenologists or andrologists working with human sperm outside urban centers; appropriate hardware to capture images and process data apparently are available.

Effect of milk replacer and rumen inert fat on growth and reproduction of Malpura ram lambs

The objective of this study was to assess the effects of milk replacer and rumen inert fat on growth, testicular development, puberty, semen production and sperm motion characteristics of ram lambs reared under intensive management in semi-arid climatic conditions. Seven-day-old male lambs of Malpura breed (n=20) were divided equally into two groups. Up to weaning, the lambs in G1 group (control) were fed concentrate, green khejri (Prosopis cineraria) leaves and cowpea (Vigna unguiculata) hay along with suckling of dams, whereas lambs in G2 group were fed reconstituted milk at 17 g/lamb per day for the 1st week and at 34 g/lamb per day from 2nd week in addition to the feed inputs given in G1. During post weaning, lambs in the G1 group were given control concentrate, whereas in G2 the control concentrate supplemented with 40 g rumen inert fat per kg of feed was offered along with dry pala (Zizyphus nummularia) and ardu (Ailanthus excelsa) leaves. BWs of lambs were recorded weekly up to 6 months of age. Ram lambs of both the groups were trained for semen collection at a weekly interval from the age of 5 months and simultaneously testicular measurements were recorded fortnightly. The feeding of milk replacer and rumen inert fat had positive (P<0.05) effects on BW, testicular length, testicular volume, semen volume, sperm concentration, mass motility, % motility, % rapid, medium or slow motile spermatozoa. However, no significant effect was observed on testicular breadth, scrotal circumference, age of puberty, sperm velocities and other CASA-derived parameters. The results of this study indicate that higher plane of nutrition in the form of milk-replacer feeding during preweaning and rumen inert fat-supplemented feed during the postweaning period to growing ram lambs enhances their growth, testicular development and semen quality.

Characteristics of high-quality Asian elephant (Elephas maximus) ejaculates and in vitro sperm quality after prolonged chilled storage and directional freezing

The in vitro quality of spermatozoa from one elephant (Elephas maximus) was examined after chilled storage and directional freezing (DF). High-quality, non-contaminated ejaculates (77.6 ± 6.0% progressive motility, 3.9 ± 1.5 µg creatinine mL–1 raw semen, 2.7 ± 0.6% detached heads) were cryopreserved after 0 (0hStor), 12 (12hStor) and 24 h (24hStor) of chilled storage. At 0 h and 6 h post-thawing, total motility, plasma membrane integrity, acrosome integrity, mitochondrial activity and normal morphology were similar (P > 0.05) across treatments. In contrast, progressive motility, rapid velocity and several kinematic parameters were lower (P < 0.05) for 24Stor compared with 0hStor at 0 h post-thaw. By 6 h post-thaw, amplitude of lateral head displacement and velocity parameters (average pathway, straight-line and curvilinear velocity) were lower (P < 0.05) for 24hStor compared with 0hStor and 12hStor. DNA integrity was high and remained unchanged (P > 0.05) across all groups and processing stages (1.6 ± 0.6% of cells contained fragmented DNA). Results indicate that DF after up to 12 h of chilled storage results in a post-thaw sperm population of acceptable quality for artificial insemination. These findings have implications for the cryopreservation of sex-sorted spermatozoa, which typically undergo more than 12 h of chilled storage prior to sorting and preservation.

Evaluation of motility, membrane status and DNA integrity of frozen–thawed bottlenose dolphin (Tursiops truncatus) spermatozoa after sex-sorting and recryopreservation

Artificial insemination (AI) with sex-sorted frozen–thawed spermatozoa has led to enhanced management of ex situ bottlenose dolphin populations. Extended distance of animals from the sorting facility can be overcome by the use of frozen–thawed, sorted and recryopreserved spermatozoa. Although one bottlenose dolphin calf had been born using sexed frozen–thawed spermatozoa derived from frozen semen, a critical evaluation of in vitro sperm quality is needed to justify the routine use of such samples in AI programs. Sperm motility parameters and plasma membrane integrity were influenced by stage of the sex-sorting process, sperm type (non-sorted and sorted) and freezing method (straw and directional) (P<0.05). After recryopreservation, sorted spermatozoa frozen with the directional freezing method maintained higher (P<0.05) motility parameters over a 24-h incubation period compared to spermatozoa frozen using straws. Quality of sperm DNA of non-sorted spermatozoa, as assessed by the sperm chromatin structure assay (SCSA), was high and remained unchanged throughout freeze–thawing and incubation processes. Though a possible interaction between Hoechst 33342 and the SCSA-derived acridine orange was observed in stained and sorted samples, the proportion of sex-sorted, recryopreserved spermatozoa exhibiting denatured DNA was low (6.6±4.1%) at 6 h after the second thawing step and remained unchanged (P>0.05) at 24 h. The viability of sorted spermatozoa was higher (P<0.05) than that of non-sorted spermatozoa across all time points after recryopreservation. Collective results indicate that bottlenose dolphin spermatozoa undergoing cryopreservation, sorting and recryopreservation are of adequate quality for use in AI.

Sperm motility activation, sperm heterogeneity and sperm-female tract interactions in Bennett's wallaby (Macropus rufogriseus rufogriseus)

Sperm-oviduct interactions in Bennett's wallaby (Macropus rufogriseus rufogriseus) were investigated using in vitro cocultures of cauda epididymal spermatozoa and oviducal epithelial cells. Kidney epithelial cells were used as non-reproductive control tissues. Spermatozoa attached to epithelial cells of both origins, but sperm survival and activity was higher when cocultured with oviducal cells. New findings during live sperm-epithelial interactions included: (1) a high frequency of reversible head movements, from linear (streamlined configuration) to T shape (thumbtack configuration) in swimming spermatozoa immediately after the start of coculture; (2) the loss of sperm tails (tail shedding) increasing with time; and (3) interrupted swimming patterns, where periods of fast movement were interspersed with slower swimming while the spermatozoa interacted with the epithelial cell surface. Sperm motility activation responses were characterised after diluting the epididymal samples in phosphate-buffered saline, medium M199 and Tyrode's medium. The results confirmed that the marsupial oviduct is able to support the viability and motility of a sperm subpopulation for at least 20 h in vitro and suggest that some spermatozoa shed their tails after binding, possibly as a result of a selective process.