Use of computer-assisted sperm motility assessment and multivariate pattern analysis to characterize ejaculate quality in Mohor gazelles (Gazella dama mhorr): effects of body weight, electroejaculation technique and short-term semen storage

Estimation of body weight in captive Amur tigers (Panthera tigris altaica)

So far, there has been no safe and convenient method to weigh the large fierce animals, like Amur tigers. To address this problem, we built models to predict the body weight of Amur tigers based on the fact that body weight is proportional to body measurements or age. Using the method of body measurements, we extracted the body measurements from four different kinds of the lateral body image of tigers, i.e., total lateral image, central lateral image, ellipse fitting image and rectangle fitting image, and then we respectively used artificial neural network (ANN) and power regression model to analyze the predictive relationships between body weight and body measurements. Our results demonstrated that, among all ANN models, the model built with rectangle fitting image had the smallest mean square error. Comparatively, we screened power regression models which had the smallest Akakai information criteria (AIC). In addition, using the method of age, we fitted nonlinear regression models for the relationship between body weight and age and found that, for male tigers, logistic model had the smallest AIC. For female tigers, Gompertz model had the smallest AIC. Consequently, this study could be applied to estimate body weight of captive, or even wild, Amur tigers safely and conveniently, helping to monitor individual health and growth of the Amur tiger populations. This article is protected by copyright. All rights reserved.

Specific Seminal Plasma Fractions Are Responsible for the Modulation of Sperm-PMN Binding in the Donkey

While artificial insemination (AI) with frozen-thawed sperm results in low fertility rates in donkeys, the addition of seminal plasma, removed during cryopreservation, partially counteracts that reduction. Related to this, an apparent inflammatory reaction in jennies is induced following AI with frozen-thawed sperm, as a high amount of polymorphonuclear neutrophils (PMN) are observed within the donkey uterus six hours after AI. While PMN appear to select the sperm that ultimately reach the oviduct, two mechanisms, phagocytosis and NETosis, have been purported to be involved in that clearance. Remarkably, sperm interacts with PMN, but the presence of seminal plasma reduces that binding. As seminal plasma is a complex fluid made up of different molecules, including proteins, this study aimed to evaluate how different seminal plasma fractions, separated by molecular weight (<3, 3-10, 10-30, 30-50, 50-100, and >100 kDa), affect sperm-PMN binding. Sperm motility, viability, and sperm-PMN binding were evaluated after 0 h, 1 h, 2 h, 3 h, and 4 h of co-incubation at 38 °C. Two seminal plasma fractions, including 30-50 kDa or 50-100 kDa proteins, showed the highest sperm motility and viability. As viability of sperm not bound to PMN after 3 h of incubation was the highest in the presence of 30-50 and 50-100 kDa proteins, we suggest that both fractions are involved in the control of the jenny's post-breeding inflammatory response. In conclusion, this study has shown for the first time that specific fractions rather than the entire seminal plasma modulate sperm-PMN binding within the donkey uterus. As several proteins suggested to be involved in the control of post-AI endometritis have a molecular weight between 30 and 100 kDa, further studies aimed at determining the identity of these molecules and evaluating their potential effect in vivo are much warranted.

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.

Estimate of in vitro embryo production based on sperm subpopulations in Senepol bulls

In cattle, in vitro embryo production (IVEP) is an important reproductive biotechnology responsible for the rapid expansion of the Senepol breed in our country. This breed has shown important results when used in crossbreeding and estimate IVEP in Senepol based on seminal analysis would be valuable for the semen cryopreservation industry, research institutes and breeders. Combining the evaluation of sperm subpopulations with analysis of other sperm attributes may help to improve fertility predictions in cattle. Therefore, the objectives of the present study were to: 1) identify and characterize motile sperm subpopulations in cryopreserved Senepol semen following the washing process carried out before in vitro fertilization, and 2) to determine an model for estimate IVEP based on sperm subpopulations in conjunction with other sperm quality analyzes. Samples of 38 cryopreserved semen from 28 Senepol bulls, chosen based on retrospective data from 386 IVEP routines, underwent the semen washing and were evaluated by the computer-assisted sperm analysis system. Sperm morphology was evaluated by wet preparation technique, and plasma and acrosomal membranes integrity, mitochondrial potential, oxidative status and chromatin resistance were analyzed by flow cytometry. After multivariate analysis of principal components and grouping, three sperm subpopulations were identified: SBP1 (fast and progressive motility), SBP2 (hyperactivated motility) and SBP3 (slow non-progressive motility). After categorization of IVEP in high, medium and low embryo yield, logistic regression analysis was applied to associate the results of subpopulations and other sperm quality variables with IVEP. The SBP1 and SBP2 variables affected embryo production, and an IVEP estimation model was generated for Senepol bulls based on these two subpopulations: embryo yield = 0.1563 + 0.0328 (SBP1) + 0.0173 (SBP2). SBP1 and SBP2 represents the absolute value of the percentage of subpopulations in semen. If the calculated value (by this equation) is close to 1, the embryo yield will be low; if is close to 2, will be medium; if is close to 3, will be high. In conclusion, three subpopulations were found for Senepol semen and, despite all analyzed variables, only SBP1 and SBP2 were included in the model to estimate IVEP in this breed.

Bilateral Intratesticular Spermatoceles in a Critically Endangered Dama Gazelle (Nanger dama mhorr)

Dama gazelles (Nanger dama mhorr) are considered critically endangered by the IUCN Red List of Threatened Species since the wild population is comprised of fewer than 200 animals. Several zoos in Europe and some private ranches in the US (Texas) maintain this species in captivity as a hedge against extinction. A routine reproductive exam on an adult male revealed bilateral cysts in the testicular parenchyma. The fluid in the cysts contained copious, moderately progressive motile spermatozoa. Following examination, the gazelle was diagnosed with bilateral intratesticular spermatoceles. Electroejaculation yielded 1.5 ml of semen containing 387 × 10⁶ total sperm with 50% motility and 45% morphologically normal sperm. The spermatoceles did not appear to cause pain or dysfunction, so no treatment was performed at this time. Since fewer than 10 animals are managed in captivity in the US, no intervention (castration/hemicastration) was considered.

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.

Investigation of in vitro measurable sperm attributes and their influence on electroejaculated bull semen with a fixed-time artificial insemination protocol in Australian Bos indicus cattle

Increasing use of fixed-time artificial insemination (FTAI) in beef cattle production has presented an opportunity for the use of fresh or chilled semen as an alternative to standard cryopreserved semen. The objective of this study was to examine in vitro sperm function and pregnancy rate of electroejaculated semen, chilled and stored for 48 hr, compared to conventionally cryopreserved semen with an optimized FTAI protocol in Brahman cattle. Semen from three Brahman bulls was collected, and aliquots were extended in either chilled (at 5°C) or frozen (LN₂ ) in a Tris-egg yolk extender base with 2.4% or 7.0% glycerol, respectively. Semen samples were assessed 48 hr after collection or post-thaw and warming, for sperm motility, in vitro sperm function and fertilizing ability, and used in a FTAI programme. The overall pregnancy rates was significantly different (p < .01) after FTAI with frozen (n = 173; 53.2%) and chilled semen (n = 174; 31.6%). In contrast, the in vitro sperm assessment showed that the chilled semen had significantly faster motility (p < .05), a higher proportion of progressively motile spermatozoa (p < .05), with significantly higher proportions of acrosome intact, viable spermatozoa (p < .01). This study showed that reasonable pregnancy rates in Brahman cattle can be achieved using FTAI with chilled semen collected using electroejaculation and stored for up to 48 hr. However, improvements in semen extenders are required in consideration of semen collection method to improve the longevity of sperm fertilizing ability to significantly increase FTAI output using chilled storage of bull semen.

Seminal plasma proteins modify the distribution of sperm subpopulations in cryopreserved semen of rams with lesser fertility

Any physiological mechanism involved in sperm selection and semen improvement has effects on heterogeneous sperm populations. This is mainly due to the fact that sperm populations within a single ejaculate have considerable heterogeneity for many variables, such as motility which is meaningful in terms of understanding how some sperm cells possess fertility advantages as compared with other cells. In the present research, initially there was a multivariate and clustering analysis used to assess sperm motility data from cryopreserved ram semen to identify subpopulations and compare the distribution of these clusters between rams with lesser and greater fertility. There were four classifications made of sperm subpopulations (clusters): CL1 fast/linear/progressive sperm; CL2 fast/non-linear sperm; CL3 very fast/linear sperm with vigorous beating and CL4 slow/non-linear sperm. Rams with greater fertility had a lesser proportion of sperm considered as "hyperactivated" (CL2) and a greater proportion of slow and non-linear sperm (CL4) than sperm of rams with lesser fertility. In addition, the effects were assessed for the capacity of seminal plasma (SP) and interacting SP proteins (iSPP) that were present during different seasons of the year to improve the distribution of sperm within subpopulations of semen from rams with lesser fertility. The iSPP and SP were obtained by artificial vagina (AV) and electroejaculation (EE) during breeding and non-breeding seasons and added to thawed semen. All the aggregates had a significant effect on the distribution of sperm subpopulations and effects differed among seasons of the year and depending on collection method used. Even though, future studies are needed to assess the contribution of each subpopulation on ram sperm fertility, it is important that a multivariate analysis be used to evaluate the effect of a treatment on sperm quality variables.

Biomarkers identified with time-lapse imaging: discovery, validation, and practical application

"Time-lapse markers," which are defined by time-lapse imaging and correlated with clinical outcomes, may provide embryologists with new opportunities for improving embryo selection. This article provides an overview of noninvasive biomarkers defined by time-lapse imaging studies. In addition to comprehensively reviewing the discovery of each time-lapse marker, it focuses on the criteria necessary for their successful integration into clinical practice, including [1] statistical and biological significance, [2] validation through prospective clinical studies, and [3] development of reliable technology to measure and quantify the time-lapse marker. Because manual analysis of time-lapse images is labor intensive and limits the practical use of the image data in the clinic, automated image analysis software platforms may contribute substantially to improvements in embryo selection accuracy. Ultimately, time-lapse markers that are based on a foundation of basic research, validated through prospective clinical studies, and enabled by a reliable quantification technology may improve IVF success rates, encourage broader adoption of single-embryo transfer, and reduce the risks associated with multiple gestation pregnancies.

Quantification and identification of sperm subpopulations using computer-aided sperm analysis and species-specific cut-off values for swimming speed

Motility is an essential characteristic of all flagellated spermatozoa and assessment of this parameter is one criterion for most semen or sperm evaluations. Computer-aided sperm analysis (CASA) can be used to measure sperm motility more objectively and accurately than manual methods, provided that analysis techniques are standardized. Previous studies have shown that evaluation of sperm subpopulations is more important than analyzing the total motile sperm population alone. We developed a quantitative method to determine cut-off values for swimming speed to identify three sperm subpopulations. We used the Sperm Class Analyzer(®) (SCA) CASA system to assess the total percentage of motile spermatozoa in a sperm preparation as well as the percentages of rapid, medium and slow swimming spermatozoa for six mammalian species. Curvilinear velocity (VCL) cut-off values were adjusted manually for each species to include 80% rapid, 15% medium and 5% slow swimming spermatozoa. Our results indicate that the same VCL intervals cannot be used for all species to classify spermatozoa according to swimming speed. After VCL intervals were adjusted for each species, three unique sperm subpopulations could be identified. The effects of medical treatments on sperm motility become apparent in changes in the distribution of spermatozoa among the three swimming speed classes.

Sperm motility patterns in Andalusian donkey (Equus asinus) semen: effects of body weight, age, and semen quality

The aims of this study were to (1) identify sperm subpopulations with specific motion characteristics in fresh Andalusian donkey ejaculates; (2) evaluate the effects of individual donkey and ejaculates within the same donkey on the distribution of the subpopulations found; and (3) explore the relationship between the age and the body weight of donkey donors, the sperm quality parameters, and the sperm subpopulations structure. Sixty ejaculates from 12 Andalusian donkeys (five ejaculates per donkey), ranging in age from 4 to 15 years, were collected. Immediately after collection, sperm characteristics (volume, sperm concentration, objective sperm motility, and sperm morphology) were assessed. Donkeys were evaluated for body weight. Significant (P < 0.05) correlations were established between the body weight of the donkeys and the pH (r = -0.52), sperm motility (percentage of motile spermatozoa: r = -0.31; percentage of progressive motile spermatozoa: r = -0.34), and total sperm abnormalities (r = 0.38). The correlations of the age with the measures of semen quality were low and not significant (P > 0.05). A multivariate clustering procedure separated 65,342 motile spermatozoa into four subpopulations: subpopulation 1, consisting of slow and nonprogressive spermatozoa (15.4%), subpopulation 2, consisting of moderately slow but progressive spermatozoa (35.9%), subpopulation 3, consisting of highly active but nonprogressive spermatozoa (18.5%), and subpopulation 4, consisting of highly active and progressive spermatozoa (30.2%). The distribution of these subpopulations varied significantly (P < 0.05) according to several parameters such as the individual donkey, the ejaculate of the same donkey, the total motility, and the overall sperm concentration. Our results show the existence of four well-defined motile sperm subpopulations in Andalusian donkey ejaculates, and suggest a high heterogeneity in the ejaculate structure in donkey. The relationship between the distribution of the sperm subpopulations and individual donkey, total motility, and sperm concentration shows that the spermatozoa of each have different motility patterns. However, the proportions of sperm subpopulations in the ejaculates did not vary with age and body weight. Finally, the study of discrete subpopulations of motile spermatozoa could lead to a substantial increase in information acquired during donkey semen analysis.

Artificial neural networks for the definition of kinetic subpopulations in electroejaculated and epididymal spermatozoa in the domestic cat

This study was designed for the identification of different sperm kinetic subpopulations in feline semen using artificial neural networks (ANNs) and for the evaluation of the effect of ejaculation on motility patterns of these subpopulations. Seven tomcats presented for routine orchiectomy were electroejaculated, and after 5 days, orchiectomized and epididymal tail sperms were collected. Sperm motility characteristics were evaluated using a computer-assisted sperm analyzer that provided individual kinetic characteristics of each spermatozoon. A total of 23 400 spermatozoa for electroejaculated and 9200 for epididymal tail samples were evaluated using a multivariate approach, comprising principal component analysis and ANN classification. The multivariate approach allowed the identification and characterization of three different and well-defined sperm subpopulations. There were significant differences before (epididymal tail spermatozoa) and after (electroejaculated sperm) ejaculation in sperm kinetic subpopulation characteristics. In both epididymal and ejaculated samples, the majority of subpopulation was characterized by high velocity and progressiveness; however, the electroejaculated samples showed significantly higher values, suggesting that the microenvironment of the epididymal tail could affect the sperm motility or, alternatively, seminal plasma could increase the kinetic characteristics of the spermatozoa, indicating that only after ejaculation, the spermatozoa express their motility potential. Nevertheless, further studies are required to clarify the functional significance of each kinetic subpopulation.

Ejaculate characteristics, short-term semen storage and successful artificial insemination following synchronisation of oestrus in the Indian blackbuck antelope (Antilope cervicapra)

The blackbuck (Antilope cervicapra) is a small (20–30 kg) Indian antelope that is listed on Schedule I of the Indian Wildlife Protection Act, 1972. Studies were undertaken to develop assisted reproductive technologies, such as synchronisation of oestrus and non-surgical AI, to support the conservation and genetic management of this Indian antelope. Semen characteristics, testosterone levels and the feasibility of short-term cold storage of semen were investigated. Furthermore, different oestrous synchronisation protocols (norgestomet implants and prostaglandin injections) were evaluated for successful AI, defined as the birth of live young. Norgestomet ear implants and i.m. administration of pregnant mare’s serum gonadotropin (PMSG) resulted in successful pregnancies in two of five inseminated females, but both had twin pregnancies that were delivered prematurely. In contrast, two injections of prostaglandin 11 days apart were effective in synchronising oestrus in the blackbuck. Transcervical AI in oestrous-synchronised animals 72 and 96 h after the second prostaglandin injection resulted in successful pregnancies in four of six inseminated females (67%) and resulted in the delivery of three live fawns. These studies demonstrate the potential application of AI technology for the conservation of endangered ungulates. To our knowledge, this is the first report regarding the synchronisation of oestrus and successful non-surgical AI in blackbuck.

Effect of different thawing rates on post-thaw sperm viability, kinematic parameters and motile sperm subpopulations structure of bull semen

The aim of the present study was to evaluate three thawing rates for bull semen frozen in 0.25-ml straws: placing the straws in a water bath at 37 degrees C for 40s, at 50 degrees C for 15s or at 70 degrees C for 5s. In a first experiment, the three thawing rates were compared in relation to post-thaw sperm motility, determined subjectively, and sperm plasma and acrosomal membrane integrity, examined by flow cytometry, after 0 and 5h of incubation at 37 degrees C. In a second experiment, the three thawing rates were evaluated based on post-thaw sperm motility, determined using a CASA system, after 0 and 2h of incubation at 37 degrees C. In addition, for the motile spermatozoa, the individual motility descriptors were analysed using a multivariate clustering procedure to test the presence of separate sperm subpopulations with specific motility characteristics in the thawed bull semen samples. Finally, it was investigated if the thawing rate had any influence on the relative frequency distribution of spermatozoa within the different subpopulations. In terms of overall post-thaw motility or plasma and acrosomal sperm membrane integrity there were no significant differences between the three thawing methods evaluated. The statistical analysis clustered all the motile spermatozoa into four separate subpopulations with defined patterns of movement: (1) moderately slow and progressive sperm (27%); (2) "hyperactivated-like" sperm (15.4%); (3) poorly motile non-progressive sperm (34.3%); (4) fast and progressive sperm (23.3%). The thawing rate had no significant influence on the frequency distribution of spermatozoa within the four subpopulations, but there was a significant effect (P<0.05) of the interaction between thawing rate and incubation time. Higher proportions of spermatozoa with fast and progressive movement were observed after 2h of post-thaw incubation when the thawing was at the faster rates (35 degrees C/40s: 8.3%, 50 degrees C/15s: 18.1% and 70 degrees C/5s: 16.5%). Whether this subtle difference might affect to the in vivo fertility of the thawed bovine semen is not known.

In vitro oocyte maturation, fertilization and culture after ovum pick-up in an endangered gazelle (Gazella dama mhorr)

The recovery of immature oocytes followed by in vitro maturation, fertilization and culture (IVMFC) allows the rescue of biological material of great genetic value for the establishment of genetic resource banks of endangered species. Studies exist on sperm cryopreservation of endangered Mohor gazelle (Gazella dama mhorr), but no work has been carried out yet on oocyte collection, fertilization and culture in this or related species. The purpose of this study was to develop a protocol for ovarian stimulation for the recovery of oocytes and subsequent IVMFC in the Mohor gazelle using frozen-thawed spermatozoa. Ovum pick-up was performed after ovarian stimulation with a total dose of 5.28 mg of ovine FSH. A total of 35 oocytes were recovered from 56 punctured follicles (62%) (N=6 females). Out of 29 cumulus-oocyte complexes matured in vitro, 3% were found at germinal vesicle stage, 7% at metaphase I, 21% were degenerated, and 69% advanced to metaphase II. Fertilization and cleavage rates of matured oocytes were 40 and 30%, respectively. Embryos cleaved in vitro up to the 6-8 cell stage but none progressed to the blastocyst stage, suggesting the existence of a developmental block and the need to improve culture conditions. Although more studies are needed to improve hormonal stimulation and oocyte harvesting, as well as IVMFC conditions, this study demonstrates for the first time the feasibility of in vitro fertilization with frozen-thawed semen of in vitro matured oocytes collected by ovum pick-up from FSH-stimulated endangered gazelles.

Multivariate Cluster Analysis Regression Procedures as Tools to Identify Motile Sperm Subpopulations in Rabbit Semen and to Predict Semen Fertility and Litter Size

Computerized motility analysis (CASA) shows that four separate subpopulations of spermatozoa with different motility characteristics co-exist in rabbit ejaculates. There were significant (p < 0.01) differences in the distribution of these subpopulations among separate genetic lines, total sperm abnormalities and the percentage of altered acrosomes. Furthermore, logistic and linear multivariate regressions among several parameters of rabbit semen quality analysis were tested for use as predictive tools for the fertilizing ability of a specific artificial insemination semen sample. Logistic regression analysis rendered two mathematical, significant (p < 0.01) models: one between sperm viability and conception rate and the other between total sperm abnormalities and conception rate. Multiple linear regression analyses also yielded some significant relationships between both fertility (p < 0.001) and litter size (p < 0.05), with respect to some semen characteristics. Our results support the hypothesis that the predictive in vivo fertility use of the standard rabbit semen quality analysis coupled with a CASA determination could be reasonably achieved by applying linear and logistic regression analyses among several parameters of rabbit semen quality analysis.

Semen Characteristics of the Captive Indian White-Backed Vulture (Gyps bengalensis)1

The present paper describes, to our knowledge for the first time, the successful collection and evaluation of semen from the Indian white-backed vulture (Gyps bengalensis), a critically endangered bird. Over a period of 2 yr, semen was collected using the manual massage method and evaluated for semen volume, semen pH, sperm concentration, percentage normal/abnormal spermatozoa, and percentage motile spermatozoa. It appears that the concentration of spermatozoa and percentage motile spermatozoa in the Indian white-backed vultures are low compared to those in other birds. Tyrode medium supplemented with albumin, lactate, and pyruvate (TALP) proved to be the best semen extender compared to two others (Beltsville Poultry Semen Extender and Lake diluent). Furthermore, TALP with 20% egg yolk and supplemented with 8% dimethyl sulfoxide maintained 50% of the initial percentage of motile spermatozoa following cryopreservation and thawing. A computer-aided semen analysis indicated that the spermatozoa of the Indian white-backed vulture are extremely active and swim in linear trajectories for up to 5 h following dilution in TALP. The trajectories were linear with time, but we noticed a decrease in the velocity parameters (average path velocity, curvilinear velocity, and progressive velocity). Thus, the present study provides baseline data on semen characteristics of the highly endangered Indian white-backed vulture, and these data could be of immense importance to reproductive and conservation biologists attempting to breed these animals in captivity, which to date has not been achieved.

Factors affecting the plasma membrane function of cooled-stored stallion spermatozoa

The spermatozoon is a highly specified cell that has the abilities of active motility and fertilization of the ovum. Damage to the sperm plasma membrane results in the irreversible loss of its functions. Because of the high content of unsaturated fatty acids in the plasma membrane, mammalian sperm are sensitive to oxidative stress. While mild peroxidation appears to promote capacitation of the sperm cell, excessive peroxidation will damage the plasma membrane and results in loss of motility and fertility. The functional integrity of the sperm plasma membrane can be determined by functional tests (determination of motility, resistance against hypoosmotic media) or different staining methods. Today, fluorescent dyes that allow the evaluation of membrane-intact cells are preferred. Computer-assisted evaluation or the use of flow cytometry has improved the precision of these methods. The use of cooled-shipped semen has become a routine method in the equine industry and semen stored at 5 degrees C for about 24 h maintains fertility close to that of fresh semen. According to the suitability of their ejaculates for cooled-storage, stallions may be classified as "good coolers" or "poor coolers". Semen processing involves a number of factors that may damage the sperm plasma membrane. This includes addition of semen extender, centrifugation, cooling and storage at a temperature of 4-6 degrees C. Extender media and their ingredients protect the sperm plasma membrane against environmental influences, but unsuitable composition of the extender can also promote membrane damage. Recent advantages in extender composition are based on the substitution of undefined factors such as milk or egg yolk by more defined and stable components.

Post mortem time and season alter subpopulation characteristics of Iberian red deer epididymal sperm

We have studied the effect of post mortem time and season on sperm subpopulation pattern and characteristics. We used epididymal samples from free-ranging Iberian red deers harvested during the hunting season. We studied samples at different moments of the year (rut, transition period and post-rut), and at different times post mortem (up to 4 days). Sperm were extracted from the cauda epididymis and their motility was evaluated by means of a CASA system. A principal component and clustering analysis were carried out to identify subpopulations. Post mortem time caused a significant decrease in motility quality, and a general deterioration in subpopulation characteristics. We found three subpopulations the first day, and the one indicating good sperm quality decreased with post mortem time until it disappeared on the fourth day. This may indicate considerable impairment of the samples after 72 h post mortem, which could compromise their use in AI programs. With regard to season, subpopulation pattern and characteristics were better in the transition and post-rut periods. Moreover, we found one subpopulation formed by mature spermatozoa, which increased from rut to post-rut. This might be a negative fact, because samples collected after the rut may undergo hypermaturation, which possibly impairs fertility. Our results are of interest for the management of wildlife germplasm banks based on post mortem sperm recovery.

Does multivariate analysis of post-thaw sperm characteristics accurately estimate in vitro fertility of boar individual ejaculates?

The objective of this study was to determine if a multivariate pattern analysis of frozen-thawed sperm characteristics of boar semen of unknown fertility, thus identifying groups of ejaculates as "good" or "bad" freezers, would estimate their fertilizing potential in an in vitro embryo production (IVP) system. Frozen-thawed spermatozoa from a single ejaculate collected from 46 boars were evaluated for sperm motility and kinematic patterns, for sperm viability and for early changes in sperm membrane stability. All data generated were used for a multivariate pattern analysis (PATN; CSIRO, Canberra, Australia) which objectively classified all ejaculates within a data set in to one of two groups, categorised as "good" (n = 25) or "bad" (n = 21) according with their freezability. In vitro matured oocytes were exposed to 2000 or 4000 frozen-thawed spermatozoa per oocyte for 6h and then cultured in embryo culture medium for either 6h (assurance of fertilization) or 7 days (to collect data on embryo development). Rates of sperm oocyte penetration and of embryo development significantly (p < 0.05) increased in a sperm:oocyte ratio-dependent manner. A similar pattern was observed when sperm characteristics were grouped. Indeed, ejaculates classified as "good" showed significantly (p < 0.05) higher rates of oocyte penetration, cleavage and of blastocyst formation than those classified as "bad". However, variation was still present among individuals (ejaculates, boars) in their ability to produce blastocysts in vitro. It is therefore concluded that despite the presence of a relationship for ejaculates with good semen quality post-thaw (thus grouped as "good") to higher IVP-results, the presence of individual variation does not allow for an accurate estimation of in vitro fertility based solely on the frozen-thawed semen quality parameters of a single ejaculate from a given boar.

Sperm motility patterns and metabolism in Catalonian donkey semen

The Sperm-Class Analyzer detected four subpopulations of spermatozoa with different motility characteristics in the ejaculate of the Catalonian donkey. Significant differences (P < 0.001) in the distribution of these subpopulations, as well as in total sperm number and percentage total motility, were seen in the diluted semen of four sampled donkeys. All the ejaculates evaluated showed excellent semen quality characteristics; the sperm they contained was more rapid than horse sperm. Principal components analysis showed sperm l-lactate production to be a good predictor of semen condition. This, plus the characteristics of the motility patterns of the different sperm subpopulations, provides an excellent overall indicator of semen quality.

Sperm Subpopulations in Iberian Red Deer Epididymal Sperm and Their Changes Through the Cryopreservation Process1

We have applied a statistical protocol based on principal component analysis, clustering methods, and discriminant analysis for the identification of sperm subpopulations in computer-assisted sperm analysis (CASA) data. Samples were obtained from the cauda epididymis of 11 Iberian red deer and cryopreserved following a standard protocol. Motility by CASA was analyzed just after sperm recovery, just before freezing, and after thawing, and eight motility descriptors for each individual spermatozoon were recorded. Sperm viability and acrosomal status were also assessed. Subpopulation analysis was performed in four sequential steps: principal component analysis using the eight motility descriptors; nonhierarchical clustering analysis (k-means) using the first two principal components; hierarchical clustering analysis (UPGMA); and selection of the final number of clusters. Three clusters were obtained for each motility analysis: slow and nonlinear; rapid and linear; and rapid, high ALH, nonlinear. We detected variations in the clusters between treatments (initial, prefreezing and postthawed). Indeed, motility increased and linearity decreased in the prefreezing analysis. A discriminant analysis isolated three descriptors that were used again in the same statistical analysis, giving four clusters that resembled the pattern found in the first classification. We also performed a clustering analysis of the males according to prefreezing/postthawed variation of total motility, viability, and acrosomal status. The proportion of the linear subpopulations in the prefreezing treatment, in both clustering analyses, correlated positively with postthawed viability recovery. Our results show that clustering analysis of CASA data gives useful and practical information that is not obtained by conventional sperm analysis.

Semen characteristics, cryopreservation, and successful artificial insemination in the Blue rock pigeon (Columba livia)

The present study was undertaken in the Blue rock pigeon (Columba livia) to evaluate the annual semen characteristics, to identify a suitable extender for semen short-term storage, to determine a protocol for cryopreservation of semen and finally to check whether intracloacal insemination would lead to the birth of a chick. Semen characteristics such as semen volume, sperm concentration, sperm motility, and percentage of normal spermatozoa were maximum during the monsoon season. TALP was observed to be the most suitable semen extender and the sperm survived best at 37 degrees C at a dilution of 1:100 in TALP. Further, cryopreservation studies on pigeon semen indicated that 8% DMSO with or without egg yolk (20%) proved to be a better cryoprotectant compared to glycerol and polyethylene glycol. In addition, the slow freezing protocol was better than the fast-freezing protocol and about 40% of the cryopreserved spermatozoa were motile following thawing. Computer-aided semen analysis indicated that pigeon spermatozoa were extremely active immediately after dilution in TALP and exhibited linear trajectories persisting up to 9h. But, with time there was a time-dependent decrease in the velocity parameters (VAP, VSL, and VCL). Cryopreserved spermatozoa following thawing also exhibited linear trajectories but had reduced velocity as evident from the significant decrease in VAP, VSL, and VCL. Further, artificial inseminations using fresh semen resulted in 45% fertilization and birth of a live chick.

Concepts in sperm heterogeneity, sperm selection and sperm competition as biological foundations for laboratory tests of semen quality

Stringent selection mechanisms, in both internal and external fertilisation systems, reject all but a significant minority of the spermatozoa released at ejaculation. Sperm competition theory provides circumstantial evidence that the selection process involves mechanisms by which the quality of the fertilising spermatozoon is controlled, thereby ensuring that females and their offspring receive high quality genetic material. In this review we examine some of these selection processes to see whether they could be exploited for the improvement of laboratory tests of sperm quality. Such tests are not only required for clinical and agricultural purposes, but are increasingly needed in fields such as reproductive and environmental toxicology where the species requirement is much broader. Despite many years of research, sperm quality assessment methods continue to provide imprecise data about fertility; here we suggest that this may be a consequence of using tests that focus on the spermatozoa that would normally be unable to fertilise under natural conditions.

To achieve fertilisation a spermatozoon must be capable of responding appropriately to external signalling stimuli; those involving protein kinase-regulated flagellar function seem especially influential in governing effects ranging from non-Mendelian inheritance in mammals to sperm chemotaxis in sea urchins. Examination of the elicited responses reveals considerable heterogeneity in all species. Here we propose that this level of heterogeneity is meaningful both in terms of understanding how spermatozoa from some individuals possess fertility advantages over spermatozoa from their rivals in sperm competition, and in that the heterogeneity should be exploitable in the development of more accurate laboratory tests.

Identification of sperm subpopulations with specific motility characteristics in stallion ejaculates

The aim of this study was to test the presence of separate sperm subpopulations, with specific motility characteristics, in stallion ejaculates by using a computer-assisted semen motility analysis (CASA) system. Motility data were analyzed with a hierarchical clustering of variables based on a correlation or covariance matrix to select like parameters of sperm motility descriptors that better explain the kinetics of spermatozoa. The statistical analyses clustered the whole motile sperm population in both fresh and 24 h stored ejaculates into four separate groups. There were significant differences in the distribution of the four subpopulations (P < 0.001) as well as in the total sperm number and the percentage of total motility (P < 0.01) in fresh semen among the five stallions tested. Our results show that separate subpopulations of spermatozoa with different motility characteristics coexist in stallion ejaculates. These subpopulations were maintained, although with a less-progressive motion pattern, after 24 h of storage. The study of subpopulations in ejaculates that have confirmed fertilizing capacity showed that the majority of the motile spermatozoa in these ejaculates are included in a subpopulation with high progressive motility and low linearity, and the ejaculates with proven fertility that have a total sperm count > or = 20 x 10(9) spermatozoa/ejaculate show all of their motile sperm included in this subpopulation. Our results show that the use of the CASA system is a relatively simple approach to the study of sperm subpopulation patterns in equine ejaculates.

Glucose- and fructose-induced dog-sperm glycogen synthesis shows specific changes in the location of the sperm glycogen deposition

Immunocytochemistry of glycogen deposition in dog sperm from fresh ejaculates showed that 53.7% of the population had glycogen at the midpiece, whereas 27.3% of the whole population accumulated glycogen only in the post-acrosomal region of the head. A similar distribution was observed when glycogen synthase, the enzyme which controls glycogen deposition, was studied. Incubation of spermatozoa with fructose increases the intracellular glycogen levels in a time- and concentration-dependent manner. Moreover, after incubation with 2 mM fructose for 30 min, 47.3% of the spermatozoa had glycogen located in both the midpiece and post-acrosomal zone, 25.4% of the population showed the polysaccharide only in the midpiece, and 24.7% of the spermatozoa showed a uniform distribution of glycogen all over the cell. Similar results were observed after incubation with 10-mM fructose. The distribution of glycogen synthase followed a similar pattern to that of glycogen. Incubation with glucose also induced a time- and concentration-dependent increase of glycogen content, whereas incubation with 2 mM glucose for 30 min showed that the majority of the population (81.2%) had the glycogen distributed throughout either the midpiece or the midpiece and the post-acrosomal zones together. There were practically no cells with a uniform glycogen distribution. Similar results were obtained after incubation with 10-mM glucose, whereas glycogen synthase suffered a similar glucose-induced distribution change. These results indicate that dog-sperm glycogen metabolism is modulated by changes in the activity of their controlling enzymes and also by changes in the specific location places where glycogen synthesis is produced.