Three Fluorescence Methods for Assessing Boar Sperm Viability

The Use of Animal's Body, Scrotal Temperature and Motion Monitoring in Evaluating Boar Semen Production Capacity

Biomedical measurements by specialized technological equipment have been used in farm animals to collect information about nutrition, behavior and welfare. This study investigates the relation of semen quality (CASA analysis, viability, morphology, membrane biochemical activity and DNA fragmentation) with boar behavior during ejaculation. Sensors were placed on the boar’s body. Movement features were collected using an inertial measurement unit (IMU), comprising an accelerometer, a gyroscope and a magnetometer. Boar, scrotal and dummy temperatures were measured by an infrared (IR) camera and an IR thermometer, while the face salivation of the boar was recorded by a moisture meter (also based on IR technology). All signals and images were logged on a mobile device (smartphone or tablet) using a Bluetooth connection and then transferred wirelessly to the cloud. The data files were then processed using scripts in MATLAB 2021a (MathWorks, Natick, Massachusetts) to derive the necessary indices. Ninety-four ejaculates from five boars were analyzed in this study. The statistical analysis was performed in the Statistics and Machine Learning Toolbox of MATLAB 2021a using a linear mixed effects model. Significant and strong negative correlations (R2 > 0.5, p ≤ 0.05) were observed between boar, dummy and scrotal temperature with the progressive, rapid and slow movement of spermatozoa, VCL (curvilinear velocity), VSL (straight line velocity) and ALH (amplitude of lateral head displacement) kinematics. The volume of the ejaculate was correlated with the scrotal and dummy temperature. Dummy’s temperature was negatively correlated with BCF (beat/cross-frequency), viability and total time of ejaculation, while it was positively correlated with abnormal morphology. Body temperature was negatively correlated with BCF. Positive correlations were noticed between VAP (average path velocity) and total time of ejaculation with body acceleration features, as well as between the overall dynamic body acceleration (ODBA) and total time of ejaculation. In conclusion, the use of biomedical sensors can support the evaluation of boar sperm production capacity, providing valuable information about semen quality.

Multivariate analyses for determining the association of field porcine fertility with sperm motion traits analysed by computer-assisted semen analysis and with sperm morphology

This study investigates the association of semen traits with boar fertility. The fertility outcome (farrowing rate - FR and total piglets born - TB) of 14 boars was obtained from a field trial conducted during 10 week of breeding period on a commercial farm using multiparous sows (n = 948) through single-sire mating with 2 × 10(9) motile sperm cells per artificial insemination (AI) dose. Sperm motion parameters, evaluated with computer-assisted semen analysis system in raw and stored semen at 17°C for 240 h, in addition to morphological sperm defects, measured on the collection day, were included in the analysis to determine which semen traits were important to discriminate the fertility potential of ejaculates from these boars. The data underwent multivariate cluster, canonical and discriminant analyses. Four clusters of boars were formed based on fertility outcome. One boar, with the lowest FR and TB values (89.7% and 11.98), and two boars, with the highest FR and TB values (97.8% and 14.16), were placed in different clusters. The other boars were separated in two distinct clusters (four and seven boars), including boars with intermediate TB (12.64 and 13.22) but divergent values for FR (95.9% vs 91.8%). Semen traits with higher discriminatory power included total motility, progressive motility, amplitude of lateral head displacement and cytoplasmatic droplets. Through multivariate discriminant analysis, more than 80% of the 140 ejaculates were correctly classified into their own group, showing that this analysis may be an efficient statistical tool to improve the discrimination of potential fertility of boars. Nevertheless, the validation of the relationship between fertility and semen traits using this statistical approach needs to be performed on a larger number of farms and with a greater number of boars.

Effect of active immunization against GnRH on testosterone concentration, libido and sperm quality in mature AI boars

Background

The aim of the present study was to investigate the efficacy of the Improvac on testosterone concentration in blood serum, sexual behavior and sperm quality in matured AI boars. A total of nine Danish Landrace AI boars were included in the analysis.

Methods

The trial period lasted for 15 weeks and was divided into four periods: Control period: three weeks before vaccination; Period I – four weeks after first vaccination; Period II – four weeks after second vaccination, Period III – four weeks after third vaccination. Blood and sperm samples were collected at weekly intervals. Freshly collected sperm samples were analyzed.

Results

Testosterone concentration correlated with libido (r = 0.531; p < 0.001), volume of ejaculate (r = 0.324; p < 0.001) and the percentage of morphologically normal spermatozoa (r = 0.207; p < 0.05). Testosterone concentration rised significantly (p < 0.05) in 5–6 week of trial, e. i. after the first dose of Improvac and after this peak the level of testosterone further progressively decreased (p < 0.05).

Conclusions

Results from this study indicate that active immunization of sexually matured boars against GnRH has negative impact on testosterone concentration, sexual behavior, volume of ejaculate and total number of normal spermatozoa in ejaculate.

Cysteine addition on short-term cooled boar semen preservation and its relationship with swine field fertility

Artificial insemination is routinely used in the swine industry to reduce the costs of production through to increase the efficiency of the refrigerated boar semen process. The objective of this study was to evaluate the effect of different levels of cysteine (CYS) added to the Beltsville Thawing Solution (BTS) extender semen during cooling for up to 72 hours. Ejaculated from three boars were collected with the gloved-hand technique and semen aliquots were diluted in BTS as follow: BTS only (BTS), BTS + 0.1mM cysteine (CYS0.1), BTS + 0.5mM cysteine (CYS0.5), BTS + 1.0mM cysteine (CYS1.0), BTS + 2.5mM cysteine (CYS2.5), BTS + 5.0mM cysteine (CYS5.0), BTS + 10.0mM cysteine (CYS10.0), and BTS + 20.0mM cysteine (CYS20.0). Evaluation of sperm integrity were analyzed using 0.5mg/ml propidium iodide (plasma membrane), 100µg/ml isothiocynate-conjugated Pisum sativun agglutinin (acrosomal membrane) and 153µM 5,5',6,6'-tetrachloro-1,1',3,3'-tetraethylbenzimidazolyl carbocyanine iodide (mitochondria potential) after semen dilution at specific times (0, 24, 48 and 72 hours). Additionally, we also evaluated the effects of 5.0 mM CYS addition in the BTS extender on the maintenance of sperm quality and their influence on fertility in the swine production. After artificial insemination, animals were evaluated based on the estrous return and the number of piglet's born. Cysteine at concentrations of 10.0 and 20.0mM resulted in more pronounced reductions even at the time zero. Semen viability decreased to levels below 10% at these high levels of CYS in the first 24 hour of storage at 17ºC. At the end of the storage time, less than 65% of sperm cells had intact plasma membrane in all groups. The sperm viability decreased significantly when the semen was added at high concentrations of CYS (time "0"; CYS10.0 and CYS20.0; p<0.05), when compared to the other CYS concentrations. The BTS (10.20±0.39) treated group showed a lower rate of estrus return when compared to other (BTSCYS; 86.05±039), and it showed also the highest total number of piglets borne per treatment (12.71±3.38 vs. 9.00±3.38, respectively). In conclusion, the addition of CYS in the BTS semen extender did not maintain spermatic viability of boar cooled spermatozoa and it results in a higher percentage of return to estrus and lower number of piglets borne.

The osmotic tolerance of boar spermatozoa and its usefulness as sperm quality parameter

Predicting the fertility outcome of ejaculates is very important in the field of porcine reproduction. The aims of this study were to determine the effects of different osmotic treatments on boar spermatozoa and to correlate them with fertility and prolificacy, assessed as non-return rates within 60 days (NRR(60d)) of the first inseminations, and litter size (LS), respectively. Sperm samples (n=100) from one hundred healthy Piétrain boars were used to assess 48 treatments combining different osmolalities (ranged between 100 and 4000 mOsm kg(-1)), different compounds used to prepare anisotonic solutions, and two different modalities: return and non-return to isotonic conditions. Sperm quality was evaluated before and after applying the treatments on the basis of analyses of sperm viability, motility, morphology and percentages of acrosome-intact spermatozoa. Statistical analyses were performed using a one-way ANOVA and post hoc Tukey's test, linear regression analyses (Pearson correlation and multiple regression) and Jackknife cross-validation. Although three conventional parameters: sperm viability, sperm morphology and the percentages of acrosome-intact spermatozoa were significantly correlated with NRR(60d) and with LS, their respective osmotic tolerance parameters (defined for each parameter and treatment regarding with negative control) presented a higher Pearson coefficient with both fertility and prolificacy in three treatments (150 mOsm kg(-1) with non-return to isotonic conditions, 200 mOsm kg(-1) with return and 500 mOsm kg(-1) using sodium citrate and non-return to isotonic conditions). We conclude that osmotic resistance in sperm viability, sperm morphology and acrosome-intactness in the treatments mentioned above could be assessed along with classical parameters to better predict the fertilising ability of a given ejaculate.

Assessment of sperm quality traits in relation to fertility in boar semen

Background

Several studies have been published where sperm plasma membrane integrity correlated to fertility. In this study we describe a simple fluorometer-based assay where we monitored the fluorescence intensity of artificially membrane-ruptured spermatozoa with a fixed time staining with fluorescent DNA dyes.

Methods

Membrane-impermeant fluorescent dyes Hoechst 33258 (H258) and propidium iodide (PI) were used to measure the fluorescence of the nucleus in artificially membrane ruptured spermatozoa and membrane-permeant dye Hoechst 33342 (H342) was used to measure fluorescence of intact spermatozoa. The concentration of spermatozoa in insemination doses varied from 31.2 × 10⁶/ml to 50 × 10⁶/ml and the average value was 35 × 10⁶/ml. Each boar was represented by three consecutive ejaculates, collected at weekly intervals. Nonreturn rate within 60 days of first insemination (NR %) and litter size (total number of piglets born) of multiparous farrowings were used as fertility measures.

Results

Sperm fluorescence intensity of H258 and H342, but not the fluorescence intensity of PI-stained spermatozoa correlated significantly with the litter size of multiparous farrowings, values being r = - 0.68 (P < 0.01) for H258, r = - 0.69 (P < 0.01) for H342 and r = - 0.38, (P = 0.11) for PI.

Conclusions

The increase in fluorescence values of membrane-ruptured H258 and unruptured H342-stained spermatozoa in boar AI doses can be associated with smaller litter size after AI. This finding indicates that the fluorescence properties of the sperm nucleus could be used to select for AI doses with greater fertilizing potential.

Identifying useable semen

The "predictors of useable semen" used in most commercial AI centers provide a very conservative estimate of the relative fertility of individual boars. Furthermore, the relatively high sperm numbers used in commercial AI practice (usually >3 x10(9) total sperm per dose of extended semen) usually compensate for reduced fertility, as can be demonstrated in some boars when lower numbers of sperm are used for AI. Differences in relative boar fertility are also masked by the widespread use of pooled semen for commercial AI in many countries. However, the need to continually improve the efficiency of pork production, suggests that commercial AI practice should involve increased use of boars with the highest genetic merit for important production traits. Necessarily, this must be linked to the use of fewer sperm per AI dose, fewer inseminations per sow bred, and hence more sows bred by these superior sires. In turn, this requires improved techniques for evaluating semen characteristics directly related to the fertilization process, such as IVM-IVF assays, analysis of seminal plasma protein markers, more discriminatory tests of sperm motility and morphology, with the goal of identifying high-index boars whose fertility is sustained when low numbers of sperm are used for AI. This paper reviews the current status of laboratory-based boar semen evaluation techniques that meet these criteria.

Fertility of frozen-thawed stallion semen cannot be predicted by the currently used laboratory methods

The aim of the project was to use current simple and practical laboratory tests and compare results with the foaling rates of mares inseminated with commercially produced frozen semen. In Exp. 1, semen was tested from 27 and in Exp. 2 from 23 stallions; 19 stallions participated in both experiments. The mean number of mares per stallion in both experiments was 37 (min. 7, max. 121). Sperm morphology was assessed and bacterial culture performed once per stallion. In Exp. 1, progressive motility after 0, 1, 2, 3, and 4 h of incubation using light microscopy, motility characteristics measured with an automatic sperm analyzer, plasma membrane integrity using carboxyfluorescein diacetate/propidium iodide (CFDA/PI) staining and light microscopy, plasma membrane integrity using PI staining and a fluorometer, plasma membrane integrity using a resazurin reduction test, and sperm concentration were evaluated. In Exp. 2, the same tests as in Exp. 1 and a hypo-osmotic swelling test (HOST) using both light microscopy and a fluorometer were performed immediately after thawing and after a 3-h incubation. Statistical analysis was done separately to all stallions and to those having ≥ 20 mares; in addition, stallions with foaling rates < 60 or ≥ 60% were compared. In Exp. 1, progressive motility for all stallions after a 2 – 4-h incubation correlated with the foaling rate (correlation coefficients 0.39 – 0.51), (p < 0.05). In stallions with > 20 mares, the artificial insemination dose showed a correlation coefficient of -0.58 (p < 0.05). In Exp. 2, the HOST immediately after thawing showed a negative correlation with foaling rate (p < 0.05). No single test was consistently reliable for predicting the fertilizing capacity of semen, since the 2 experiments yielded conflicting results, although the same stallions sometimes participated in both. This shows the difficulty of frozen semen quality control in commercially produced stallion semen, and on the other hand, the difficulty of conducting fertility trials in horses.

Assessment of boar semen quality in relation to fertility with special reference to methanol stress

The relationship between various semen evaluation tests and fertility in fertile and subfertile artificial insemination (AI) boars was examined. In total, 36 boars, 19 Finnish Landrace and 17 Yorkshire, were included. The average value of three ejaculates extended in an X-cell extender from each boar was used in the analysis. Based on nonreturn results (NR60d, later referred to nonreturn rate, NR%), the boars were divided into two groups: those with poor fertility (NR% < 80, n = 19) and those with normal or above average nonreturn rates (NR% = 83, n = 17). Semen quality was determined after 1 and 7 days of storage at 17 degrees C. Sperm motility before and after each methanol stress was assessed both subjectively and using a computer-assisted semen analyzer (CASA). The sperm cells were stained with calcein AM and propidium iodide and evaluated for plasma membrane integrity under an epifluorescence microscope. Propidium iodide and Hoechst 33258 dyes were used in parallel to stain sperm cells for fluorometric analysis with an automatic fluorometer. Sperm morphology was evaluated in stained smears. The percentage of sows reported as not having returned to estrus within 60 days after AI (nonreturn rate, NR%) and litter size of primiparous and multiparous farrowings were used as measures of fertility. Of the parameters analyzed, only CASA-assessed total sperm motility and methanol-stressed total sperm motility correlated significantly (P < 0.05) with nonreturn rate. Those tests presenting the highest correlation with nonreturn rate were CASA-assessed total motility (r = 0.54, P < 0.01) and subjective sperm motility (r = 0.52, P < 0.01) after 7 days of storage. The highest correlation with fertility at 1 day of storage was shown by methanol-stressed total sperm motility assessed with the CASA (r = 0.46, P < 0.01). The only semen parameter that correlated significantly (r = 0.37, P < 0.05) with litter size of multiparous farrowings was viability of seven-day stored semen stained with Hoechst 33258 and analyzed with a fluorometer. The methanol stress test described here could serve as a rapid test whose results could be used to predict NR% better than motility.

Development of a protocol for multiple staining with fluorochromes to assess the functional status of boar spermatozoa

The aim of this study was to design a simple and reliable method for the simultaneous evaluation of the nucleus, the acrosome, and the mitochondrial sheath of boar spermatozoa. Sperm samples coming from healthy and sexually mature Pietrain boars were incubated with two nuclear fluorochromes--bis-benzamide specific for viable cells, and propidium iodide specific for nonviable cells--the fluorochrome Mitotracker Green FM specific for functional mitochondria, and the lectin Trypsin inhibitor from Soybean (SBTI) conjugated with the fluorochrome Alexa Fluor 488 specific for proacrosin. The results obtained from assessing the functional status of the spermatozoa using fluorochromes were compared with the conventional sperm parameters of sperm vitality using the eosin exclusion test (EE test), and sperm motility and morphology using the computer-assisted semen analyzer SCA 2002Producció. Applying the multiple staining test, it was found that the frequency of viable spermatozoa with intact acrosome and intact mitochondria was not different from the frequency of viable spermatozoa obtained with the EE test, and also correlated positively with the frequency of motile spermatozoa and the frequency of mature spermatozoa. Therefore, this technique is useful to characterize the status of boar spermatozoa by assessing the nuclear, acrosomal, and mitochondrial integrity. Moreover, it provides reliable diagnostic information about the fertility potential of boars.

Quality control in boar semen production by use of the FACSCount AF system

A simple and rapid flow cytometric method has recently been developed for simultaneous determination of sperm concentration and viability in semen from domestic animals. Use of SYBR-14 trade mark in combination with propidium iodide (PI) allows estimation of the proportion of live sperm (viability). An internal standard of fluorescent microspheres (beads) makes it possible to determine the sperm concentration during the same analysis. In the first experiment, the relationship between sperm viability and litter size was investigated. The second experiment explored whether a smaller variation in the number of motile sperm per insemination dose could be obtained using the FACSCount AF flow cytometer than using a spectrophotometer. Results in the first experiment show that sperm viability is closer related to litter size than is the traditionally used motility parameter. Although the flow cytometer is precise and objective, a limited effect on litter size should be anticipated if ejaculates are selected for insemination according to the percentage of viable sperm. However, the present trial used large insemination doses (2.3 x 10(9) motile sperm/dose) which partially compensate for the differences in motility and viability between boars and ejaculates. In the second experiment it was found that variation in the number of motile sperm per insemination dose could be reduced significantly if the FACSCount AF flow cytometer rather than the Corning 254 spectrophotometer was used for determination of sperm concentration in the raw semen. It is concluded that the FACSCount AF flow cytometer is a strong tool for improvement of the quality control in artificial insemination (AI) centres.

Use of chromatin stability assay, mitochondrial stain JC-1, and fluorometric assessment of plasma membrane to evaluate frozen-thawed ram semen

Cryopreservation of semen imposes deleterious effects on spermatozoa, either killing a certain proportion of cells or causing subtle damages on sperm function in the surviving population, changes not easily revealed by conventional assays. We have tested three functional assessment techniques in frozen-thawed ram semen from six adult rams, cryopreserved following eight different protocols (four extenders, and glycerol being added at two temperatures). Semen samples were thawed and the following analyses were carried out: motility (CASA), membrane integrity (Hoescht 33258 and fluorometry), chromatin status (chromatin stability test and fluorescence-assisted cell sorting, FACS) and mitochondrial activity (JC-1 and FACS). Fluorometry outcome did not correlate with the other parameters and showed large variation, albeit discriminating among cryopreservation techniques (P < 0.01). Mitochondrial activity correlated, but with low values, with total and progressive motility. However, good sperm motility and high velocity values were associated to high mitochondrial membrane potential. The chromatin stability assay was also successfully carried out, and had a good relationship with male factor (%COMP alpha(t) and SD alpha(t) parameters). In conclusion, fluorometric assessment of membrane integrity albeit rendering poor results, merits improvement, being a low-cost and handy technique, especially for work in the field. On the other hand, both assessments of chromatin stability and mitochondrial status (JC-1 staining), combined with FACS, are reliable techniques that can be used for the functional assessment of frozen-thawed ram semen.

Membrane status and in vitro capacitation of porcine sperm preserved in long-term extender at 16 degrees C

Preservation of porcine semen in long-term extenders at 15-18 degrees C for more than 5 days results in decreased farrowing rates and reduced litter size after artificial insemination, despite the high progressive motility rates of sperm. To improve this preservation system it is necessary to understand sperm physiology under storage conditions. The purpose of this study was to determine the effect of storing diluted porcine semen (during 0, 2, 4, 6, and 8 days) on the sperm membranes status and the ability of sperm to respond to in vitro capacitation treatment. Ten semen samples from 5 adult boars were analyzed. Two aliquots were obtained from the sperm-rich fraction: one was used to assess fresh semen and the other was diluted in Reading extender and stored at 16 degrees C. Both semen samples were stained with chlortetracycline to assess the status of sperm membranes and with Hoechst 33258 to determine viability. Semen storage for 4-8 days increased the proportion of prematurely capacitated sperm. After 4 days of storage, in vitro capacitation treatment did not increase the percentage of capacitated sperm, but increased the percentage of acrosome reacted sperm. This phenomenon could explain the reduced fertilizing ability of porcine semen stored at 16 degrees C for over 4 days, in spite of the acceptable sperm viability and progressive motility.

Validation of the FACSCount AF system for determination of sperm concentration in boar semen

A flow cytometric method has been developed for rapid determination of sperm concentration in semen from various mammalian species.* All cells containing DNA are stained with SYBR-14 or propidium iodide (PI) and sperm concentration is determined in relation to an internal standard of fluorescent microspheres (beads). Satisfactory staining can be achieved within 2-3 min and the following flow cytometric analysis on the FACSCount AF System rapidly provides the user with a precise and accurate assessment of the sperm concentration. In this study, the FACSCount AF System and Sperm Counting Reagent (BD Biosciences) was compared with microscopic counting using a Bürker-Türk haemocytometer. In addition, sperm concentration was determined using the Corning 254 spectrophotometer which is used routinely by Danish artificial insemination stations for boars. The results show that the agreement between flow cytometry and microscopic counting is very high. The slope for the regression line was 1.12 (SE = 0.03) with an estimated intercept with the Y-axis of 22 x 10(6) sperm/ml (SE = 10 x 10(6) sperm/ml) and an estimated error of the model of 10 x 10(6) sperm/ml. For the spectrophotometer, the slope of the regression line was 1.09 (SE = 0.07) with an estimated intercept of 137 x 10(6) sperm/ml (SE = 25 x 10(6) sperm/ml). The average error made by the spectrophotometer was 55 x 10(6) sperm/ml. In addition, the results obtained using flow cytometry was highly repeatable (CV = 2.7%) in comparison with the spectrophotometric method (CV = 6.3%). These results indicate that the FACSCount AF System is a valuable tool for precise and accurate assessment of sperm concentration in boar semen and that use of this system may lead to production of more uniform insemination doses containing a specific number of sperm per dose.

A novel automated fluorometric assay to evaluate sperm viability and fertility in dairy bulls

The artificial insemination (AI) industry is in need of an objective and rapid, but inexpensive method to evaluate frozen thawed bull semen ejaculates. This study presents a new fluorescence method that uses an automatized fluorometer and fluorophore stain propidium iodide that stains only those cells with damaged membranes. The fluorescence of the semen sample and the totally killed subsample were measured simultaneously, and viability was calculated. Every semen batch was analyzed before use in AI. For fertility evaluation, the nonreturn rates (NR%) obtained from 92,120 inseminations with the analyzed batches were recorded from 166 bulls (436 batches). This study confirms a 3.9% better NR% for the Finnish Holstein-Friesian breed than for Finnish Ayrshire. There was a clear seasonality in NR%: it differed (5.3%) significantly, being best in summer to autumn (June to October) and lowest in winter (January to March). The fluorometer method was fast and easy. The correlation between the total number of viable spermatozoa in an insemination dose and field fertility was low but significant (r = 0.051, P = 0.016), suggesting that the plasma membrane integrity evaluation can serve as a cost-beneficial quality control method of frozen-thawed semen at bull stations.

Isolation of toxigenic Nocardiopsis strains from indoor environments and description of two new Nocardiopsis Species, N. exhalans sp. nov. and N. umidischolae sp. nov

Nocardiopsis strains were isolated from water-damaged indoor environments. Two strains (N. alba subsp. alba 704a and a strain representing a novel species, ES10.1) as well as strains of N. prasina, N. lucentensis, and N. tropica produced methanol-soluble toxins that paralyzed the motility of boar spermatozoa at <30 microg of crude extract (dry weight) x ml(-1). N. prasina, N. lucentensis, N. tropica, and strain ES10.1 caused cessation of motility by dissipating the mitochondrial membrane potential, Deltapsi, of the boar spermatozoa. Indoor strain 704a produced a substance that destroyed cell membrane barrier function and depleted the sperm cells of ATP. Indoor strain 64/93 was antagonistic towards Corynebacterium renale. Two indoor Nocardiopsis strains were xerotolerant, and all five utilized a wide range of substrates. This combined with the production of toxic substances suggests good survival and potential hazard to human health in water-damaged indoor environments. Two new species, Nocardiopsis exhalans sp. nov. (ES10.1T) and Nocardiopsis umidischolae sp. nov. (66/93T), are proposed based on morphology, chemotaxonomic and physiological characters, phylogenetic analysis, and DNA-DNA reassociations.