Effects of semen extender and semen processing on motility and viability of frozen-thawed dog spermatozoa

Genetic Selection Approach for Semen Characteristics in Thai Native Grandparent Roosters (Pradu Hang Dum) Using Random Regression Test-Day Models and Selection Indices

The aim of this study was to analyze suitable genetic models and selection indices to estimate the genetic parameters and breeding values of native Thai roosters. A total of 3475 records of seven semen traits (mass movement, semen pH, semen color, volume, sperm viability, sperm abnormalities, and sperm concentration) from 242 Thai native grandparent roosters were analyzed. Multiple-trait random regression test-day models with five covariance functions were used to analyze the variance components, genetic parameters, and breeding values. The selection index (SI) was calculated to determine the optimal genetic value for different selection percentages. The results showed that a multiple-trait random regression test-day model with a second-order Legendre polynomial function was the most appropriate genetic model for this population. The estimated heritability values were low to moderate, ranging from 0.110 to 0.112 (mass movement), 0.040 to 0.051 (semen pH), 0.092 to 0.097 (semen color), 0.220 to 0.225 (semen volume), 0.067 to 0.083 (sperm viability), 0.086 to 0.099 (sperm abnormalities), and 0.134 to 0.138 (sperm concentration). The repeatability values exceeded the heritability values and were within the range of 0.133 to 0.688. The genetic correlations among semen traits ranged from -0.332 to 0.677, and phenotypic correlations ranged from -0.260 to 0.460. When considering heritability and genetic correlation values, semen volume, sperm concentration, and mass movement were the top three priority semen traits calculated as selection indices. Finally, the top 10% of the selection index was recommended for creating the next generation. Our findings provide useful information on genetic parameters and an appropriate selection index of semen traits for selecting the genetics of individual Thai native grandparent roosters. The heritability estimates for semen traits reported here suggest an adequate response to selection through a genetic evaluation approach. Our results indicate that it is possible to select grandparent roosters with better reproductive performance.

Double semen collection at a 1-h interval in dogs decreases the bacterial contamination of canine ejaculates

Semen extenders usually contain antibiotics with the aim to minimize bacterial growth, but the indiscriminate use of antibiotics increases the emergence of multidrug-resistant bacteria. A limiting factor of semen processing in dogs is the low total sperm count that limits the number of insemination doses that can be obtained from one ejaculate. Therefore, two ejaculates collected at a short interval can be combined to increase the number of AI doses. In this study, semen was collected from dogs either once or the same dogs (n = 28) were submitted to dual semen collection 1 h apart. All ejaculates were submitted to bacteriological analysis. We hypothesized that bacterial contamination of semen is low but that a dual semen collection might increase contamination. A sample for bacteriological examination was taken from raw semen immediately after semen collection. Bacteria including mycoplasmas were isolated using conventional cultivation procedures and isolates were identified to the species level by matrix-assisted laser desorption ionization - time of flight (MALDI-ToF) mass spectrometry. In total, 22 bacterial species were identified in the 84 ejaculates with Mycoplasma cynos, Streptococcus canis and Canicola haemoglobinophilus being most frequent. Bacterial growth was sporadic in 16 and absent in 10 ejaculates. The overall bacterial growth was lower in the second than in the first ejaculate of dual semen collections (p < 0.05). The percentage of motile and membrane-intact spermatozoa in frozen-thawed ejaculates was not associated with the degree of bacterial contamination of raw semen. In conclusion, there was only limited microbial contamination in dog semen and the microorganisms isolated are considered part of the normal genital bacterial flora. Repeated semen collection reduced bacterial contamination in the second in comparison to the first ejaculate. The use of antibiotics in canine semen should be questioned.

Investigation of the Efficacy of Dithiothreitol and Glutathione on In Vitro Fertilization of Cryopreserved Large White Boar Semen

The objectives of this study were to evaluate the properties of sperm motility and morphology under induced oxidative stress, compare the antioxidant capacity of dithiothreitol (DTT) and glutathione (GSH) following the cryopreservation of Large White boar semen, investigate the ability of cryopreserved Large White boar semen to fertilize the matured gilts oocytes and compare the efficacy of DTT and GSH antioxidants in improving the oocyte fertilization by cryopreserved Large White boar semen. The semen was collected from three Large White boars (ten ejaculates per boar) and transported (37 °C) to the laboratory. Semen freezing extenders were supplemented with 5 mM DTT, 5 mM GSH and a combination of 2.5 mM DTT + 2.5 mM GSH. A liquid nitrogen vapor method was used to freeze boar semen. Gilts’ ovaries were collected from the local abattoir and transported (37 °C) to the laboratory. The slicing method was used to retrieve the oocytes from the ovaries. Fresh semen and frozen-thawed semen were used for in vitro fertilization (IVF). For frozen-thawed semen, four treatments (control, 5 mM DTT, 5 mM GSH, and a combination of 2.5 mM DTT + 2.5 mM GSH) were used during IVF in order to evaluate the fertilizing ability of the antioxidants. The supplementation of 5 µM DTT to H2O2-treated semen significantly improved progressive motility (PM) by 14.82%. A combination of 2.5 mM DTT + 2.5 mM GSH treatment reduced percentage of sperm total motility (TM) and rapid motility (RAP) following thawing (p < 0.05). Fresh semen and a combination of 2.5 mM DTT + 2.5 mM GSH treatment recorded a higher percentage of zygotes with polyspermy (p < 0.05). The control treatment numerically recorded a high percentage of zygotes with 1 PN, while the 5 mM DTT treatment recorded a high percentage of zygotes with 2 PN.

Influence of Single Layer Centrifugation with Canicoll on Semen Freezability in Dogs

Simple Summary

Freezing dog semen is not always possible due to low quality sperm or poor survival during freezing. In order to make this assisted reproductive technique available to a larger number of dogs, this study investigated the benefit of selecting the best spermatozoa before freezing using single layer centrifugation (SLC). The results indicated that this technique was effective in separating spermatozoa according to their quality, although this resulted in losing some good quality spermatozoa. After thawing, spermatozoa centrifuged by SLC were of better quality than after standard centrifugation. However, spermatozoa from suboptimal quality semen did not survive freezing as well as spermatozoa from semen of optimal quality, even after SLC. Single layer centrifugation, therefore, makes it possible to obtain better quality spermatozoa after thawing but is not sufficient on its own to improve the inferior freezing ability of spermatozoa from suboptimal quality semen. So far, eighteen pups were born after insemination with SLC-selected frozen-thawed semen, proving that these selected spermatozoa remain fertile.

Abstract

This study evaluated how semen selection by single layer centrifugation (SLC) with Canicoll affects semen freezability in dogs. A total of eighteen ejaculates, collected from dogs with optimal and suboptimal semen quality (optimal: normal morphology (NM) ≥ 80%, n = 9; suboptimal: NM between 60 and 79%, n = 9), were divided into two aliquots and subjected to standard centrifugation or SLC before cryopreservation. Motility, NM, membrane integrity, mitochondrial membrane potential (MMP), and DNA integrity were improved in fresh samples after SLC, regardless of semen quality, but at the expense of some good quality spermatozoa. After thawing, NM and membrane integrity were improved in SLC-selected semen in both semen qualities. Interestingly, MMP was also higher but only in optimal quality semen. Still, spermatozoa from suboptimal quality semen did not survive freezing to the same extent as spermatozoa from optimal quality semen, even after selecting superior spermatozoa. Semen selection with Canicoll is, therefore, an effective technique to isolate a subpopulation of high-quality spermatozoa and obtain sperm samples of better quality after thawing, but is not sufficient to improve the intrinsic inferior freezability of suboptimal quality semen. So far, eighteen pups were born after insemination with SLC-selected frozen-thawed semen, proving that these selected spermatozoa remain fertile.

Effects of age, size and season on cryotolerance of dog semen - A retrospective analysis

In a retrospective analysis of 508 ejaculates from 297 dogs, efficiency of semen cryopreservation and effects of age, season and dog size on characteristics of fresh and cryopreserved semen were evaluated. Volume of the sperm-rich ejaculate fraction increased to 10 years of age, decreased in 10 and 11-year old dogs (P < 0.001) but did not differ among seasons. Total sperm count was less in 10 and 11-year-old dogs (P < 0.001). The percentage of progressively motile, membrane-intact and morphologically normal spermatozoa before cryopreservation was least in 10 and 11-year-old dogs (P < 0.001). Cryopreservation resulted in less progressively motile spermatozoa (P < 0.001) with this being most pronounced in 10 and 11-year-old dogs (cryopreservation x age P = 0.004). The cryopreservation-induced decrease in morphologically normal spermatozoa (P < 0.001) was not affected by dog body weight. Number of cryopreserved AI doses differed among age groups (P < 0.001) and was less in 10 and 11-year-old dogs (median 1.5) compared with younger dogs (6-7 years, median 4.3). When ejaculates were grouped by a threshold of ≥ 35% progressively motile spermatozoa after freezing-thawing, 86.5% of all ejaculates were greater the threshold but this percentage decreased to 66% in 10 and 11-year-old dogs (P < 0.001). In conclusion, sperm cryotolerance is consistent for much of a dog´s lifespan but decreases after a certain age. Dog semen can be cryopreserved successfully throughout the year. Post-thaw semen characteristics were not different among cryopreserved ejaculates obtained from dogs differing in body weight.

Assisted reproductive techniques for canines: preservation of genetic material in domestic dogs

Assisted reproductive techniques (ARTs), such as artificial insemination, in vitro fertilization, and cryopreservation of gametes/zygotes, have been developed to improve breeding and reproduction of livestock and for the treatment of human infertility. Their widespread use has contributed to improvements in human health and welfare. However, in dogs, only artificial insemination using frozen semen is readily available as an ART to improve breeding and control genetic diversity. A recent priority in sperm cryopreservation is the development of alternatives to egg yolk, which is widely used as a component of the sperm extender. Egg yolk can vary in composition among batches and is prone to contamination by animal pathogens. The latter can be a problem for international exchange of cryopreserved semen. Low-density lipoprotein and skim milk are promising candidates for use as extenders, to ensure fertility after artificial insemination. Although not tested for its effects on fertility following artificial insemination, polyvinyl alcohol may also be a useful alternative to egg yolk as an extender. The development of cryopreservation techniques for canine embryos lags behind that for other mammals, including humans. However, given the success of non-surgical embryo transfer in 2011, studies have sought to refine this approach for practical use. Research on sperm cryopreservation has yielded satisfactory results. However, investigation of other approaches, such as cryopreservation of oocytes and gonadal tissues, remains insufficient. Techniques for the efficient induction of estrus may aid in the development of successful canine ARTs.

Combined cryopreservation of canine ejaculates collected at a one-hour interval increases semen doses for artificial insemination without negative effects on post-thaw sperm characteristics

A limiting factor in canine artificial insemination (AI) is the low number of insemination doses obtained per ejaculate. In this study, semen was collected from dogs (n = 28) either once and frozen directly after collection or the same dogs were submitted to a dual semen collection with a 1‐hr interval and the two ejaculates were combined for cryopreservation. We hypothesized that combining two ejaculates increases semen doses per cryopreservation process without negative effects on semen characteristics. Total sperm count was lower in semen from a single semen collection in comparison with the combination of the first and second ejaculate of a dual semen collection (p < .001). The percentage of motile and membrane‐intact spermatozoa determined by computer‐assisted sperm analysis (CASA) in raw semen did not differ between single and combined dual ejaculates and was reduced (p < .001) by cryopreservation to the same extent in single (motility 73.7 ± 1.8%, membrane integrity 65.6 ± 2.2%) and combined dual ejaculates (motility 72.7 ± 2.3%, membrane integrity 64.6 ± 2.5%). The percentage of spermatozoa with morphological defects increased after cryopreservation (p < .001) but was similar in single and combined dual ejaculates. The CASA sperm velocity parameters decreased with cryopreservation (p < .001) but did not differ between single and combined dual ejaculates. The number of insemination doses increased from 2.7 ± 0.4 for single to 4.7 ± 0.8 for combined dual ejaculates (p < .01), based on 100 million motile spermatozoa per frozen‐thawed semen dose. In conclusion, combining two ejaculates collected at short interval for one cryopreservation process increases the number of AI doses without compromising semen quality.

Antioxidant effects of supplementation of 3,4-dihydroxyphenyl glycol on sperm parameters and oxidative markers following cryopreservation in canine semen

Supplementing the extender with antioxidants with low molecular weight can enhance the quality of the post-thaw sperm during the freezing process. This study was aimed at determining the impacts of 3,4-dihydroxyphenyl glycol (DHPG) on the spermatozoa of the canine undergoing freeze-thawing process. In this study, 24 ejaculates were obtained from three mixed-breed dogs and were diluted in a Tris-based extender. The diluted semen was divided into aliquots for supplementation of 10, 30, 50 and 70 µg/ml of DHPG, control (without antioxidant) and control sham (DMSO). After being extended, the semen was equilibrated at a temperature of 4°C and then transferred to the straws and kept 4 cm above the liquid nitrogen for 20 min and was finally immersed in the liquid nitrogen. They were cryopreserved for seven days; then, sperm parameters including sperm motility evaluation, motility characteristics, viability, DNA and plasma membrane integrity, total antioxidant capacity (TAC), reduced glutathione content (GSH), antioxidant enzymes (superoxide dismutase [SOD], catalase [CAT] and glutathione peroxidase [GPx]) activity malondialdehyde (MDA) levels were evaluated. This study showed that spermatozoa cryopreservation with 50, 30 and 70 µg/ml of DHPG concentrations had better progressive motility, Curvilinear Velocity, Linearity, viability, intact plasma membrane and the levels of TAC, GPx and GSH were higher than the control group. The 50, 30 and 70 µg/ml of DHPG concentrations led to the significant decrease of DNA damage compared to the control group. Total motility, average path velocity, straight-line velocity and CAT activity were significantly improved in 30 and 50 µg/ml of DHPG concentrations, compared to the control group. Also, the 50 and 30 µg/ml of DHPG concentrations, decreased MDA levels compared to the other groups, significantly. In conclusion, our study showed that the addition 50 µg/ml of DHPG to the canine semen extender improved the semen characteristics and oxidative markers in the cryopreservation process.

Using egg yolk in a TRIS-Equex STM paste extender for freezing of dog semen is superior to egg yolk plasma, also after addition of lecithin and catalase

We compared the results of using egg yolk plasma (EYP) instead of egg yolk (EY) in a TRIS-based Equex STM Paste freezing extender system for dog semen [25]. We also tested whether the addition of lecithin and catalase to the EYP extenders would improve results. Fractionated semen collection was done in 17 stud dogs and the sperm rich fraction diluted with different extenders in 2 steps: (I) TRIS-fructose-citric acid extender (TRIS) containing 20% egg yolk (EY) and 3% glycerol [25], (II) TRIS containing 20% egg yolk plasma (EYP) and 3% glycerol, and (III) TRIS containing 20% EYP and 0.8% lecithin (EYP-L) and 3% glycerol. After equilibration the second dilution step was done: samples with (I) were diluted with TRIS-EY with 7% glycerol and 1% Equex STM paste [25]; samples with (II) and (III) were divided in 2 aliquots each, and one part diluted with TRIS-EYP or TRIS-EYP-L, both containing 7% glycerol and 1% Equex STM paste, and the other one part with the same extenders containing additionally 300 I.U./mL catalase. After freezing and thawing, samples were analyzed by CASA and sperm chromatin structure assay (SCSA); reactive oxygen species (ROS), degree of apoptosis and zona binding ability were determined. Semen samples with TRIS-EY with a final concentration of 5% glycerol and 0.5% Equex STM paste [25] showed best post thaw progressive motility (P), most intact cells, lowest percentage of ROS, acrosome damages, dead and apoptotic cells. Curvilinear velocity (VCL), DNA fragmentation, morphological abnormalities and zona binding ability did not differ between groups. Replacement of egg yolk by EYP increased the ROS and late apoptotic cells. Addition of lecithin and catalase to EYP containing extenders decreased motility and increased complete apoptosis. We conclude that egg yolk is superior to EYP in the here investigated extenders. The TRIS-based extender [25] with EYP could not be improved by addition of lecithin and catalase; however, in-vivo fertilization capacity of the here examined extenders remains to be investigated.

The ABCA1 blocking agent probucol decreases capacitation in ejaculated dog spermatozoa

BACKGROUND

The ATP binding cassette (ABC) transporters participate in the cholesterol and phospholipid transport within and through cell membranes of many cells including spermatozoa. Cholesterol efflux is important for capacitation of spermatozoa. ABCA1 expression has been assessed in canine spermatozoa previously but its role in capacitation still has to be determined. The aim of the study was to test whether inhibition of ABCA1 (1) decreases capacitation in ejaculated and epididymal canine sperm samples and (2) decreases cholesterol efflux in the same samples. Twenty-one ejaculates and sperm from 22 epididymal tails were collected from healthy dogs. Motility was measured by CASA and viability assessed after staining with SYBR-14/PI. Samples from ejaculated sperm and sperm from epididymal tails were aliquoted. One part was incubated with the ABCA1 inhibitor probucol, the other served as a negative control. In all samples, capacitation was evaluated by chlortetracyclin (CTC) assay and cholesterol was measured by cholesterol efflux assay and colorimetric enzymatic assay.

RESULTS

In ejaculated sperm, blockade of ABCA1 with 100 µM of probucol/mL of sample resulted in a significantly higher percentage of uncapacitated and acrosome reacted spermatozoa (P < 0.001 and P = 0.031), capacitation was significantly decreased (35% in probucol samples vs 54.2% in controls, P < 0.001). In probucol inhibited sperm samples from epididymal tails, the percentage of capacitated spermatozoa did not differ between groups but the percentage of acrosome reacted spermatozoa increased significantly (P = 0.014). The cholesterol measurement revealed significantly lower cholesterol concentration in the probucol group when compared to the controls (P = 0.035), however only in ejaculated sperm samples.

CONCLUSIONS

CTC assay and cholesterol measurement revealed significant differences between groups; we conclude that inhibition of ABCA1 significantly decreased capacitation and cholesterol efflux in ejaculated canine spermatozoa. The inhibition was not complete but ABCA1 is supposed to contribute to capacitation in canine ejaculated spermatozoa. ABCA1 is probably not important for capacitation of epididymal spermatozoa but might exert other functions during spermatozoa ripening.

The Effect of N-N-Dimethylformamide on the Membrane Characteristics of Canine Spermatozoa After Cryopreservation, and its Relationship With Post-Thaw Motility

Some studies have demonstrated that glycerol is superior to amides in preserving sperm motion characteristics of canine sperm; however, little is known about the effect of these cryoprotectants on the membrane characteristics of canine spermatozoa after freezing/thawing. In this study, the effects of using either N-N-dimethylformamide (DMF) or glycerol (GLY) on the integrity and function of the canine sperm, after cryopreservation were determined. We hypothesized that the use of a multiparametric approach for assessing the effect of DMF on the membranes of canine sperm would explain the lower values reported for post-thaw motility. Ejaculates from 12 dogs were collected, split into 2 groups, and frozen using a tris-fructose-citrate-egg yolk-based extender containing either 7% (v/v) GLY or 7% (v/v) DMF. Frozen straws (n = 120) were thawed and analyzed for subjectively-assessed sperm progressive motility, normal morphology, plasma membrane integrity, plasma membrane function (HOST+), acrosome membrane integrity, high mitochondrial membrane potential, and simultaneous assessment of sperm membrane integrity and function by a triple-staining fluorescent procedure. Overall, sperm motility and membrane intactness/function were higher when GLY was used as a cryoprotectant, as compared to DMF (P < .05). A model to explain the variation in progressive motility using the values obtained from the sperm integrity and function parameters was designed. The percent HOST+ sperm and high mitochondrial membrane potential sperm were mostly associated with the changes observed in the progressive motility (r² = 0.84; P = .043) when either GLY or DMF were used as cryoprotectants. These results may explain the overall reduced sperm quality observed after cryopreservation, as a reflection of sublethal damage sustained by the sperm membranes.

Effect of cholesterol loaded cyclodextrin on semen cryopreservation of Aksaray Malakli shepherd dogs of different ages

The objective of the study was to determine the effect of cholesterol-loaded cyclodextrin (CLC) on the quality parameters of semen from Aksaray Malakli Shepherd dogs of different age groups. Forty-eight male dogs were divided into 3 groupings according to their ages (young age (Y): ≤3 years, n: 20; middle age (M): 4-6 years, n: 20; old age (O): ≥7 years; n: 8). The sperm-rich portion of the ejaculate from each dog was divided into four aliquots and extended with either tris as a control (C) or tris loaded with 0.5, 1.0, and 1.5 mg/120 × 10⁶ CLC as low (L), intermediate (I), and high (H) doses, respectively. Following equilibration for at least half an hour, the straws were frozen in nitrogen vapor and then stored in liquid nitrogen at least for 48 h. Later, the frozen straws were thawed in a water bath for spermatological evaluation. Significant differences were observed between different age groups in terms of the spermatological parameters (p < 0.05). The evidence suggests that increasing age is associated with poor in-vitro spermatological parameters and CLC was able to protect the acrosome integrity from cryo-damage during the freeze-thawing process. Better semen freezability characteristics were obtained at young ages, considering the overall parameters.

The influence of caffeine supplementation and concerted utilization of enzymatic and mechanical semen liquefaction on freezability of dromedary camel spermatozoa

Assisted reproductive technologies have been reported to improve reproductive efficiency and genetic potential in camelids. Two experiments were carried out to determine efficiency of centrifugation in the presence of a mucolytic agent for liquefaction of dromedary semen. In the first experiment, three groups, namely: I. Tris lactose (TL, control), II. Tris lactose supplemented with amylase (TL_A) and III. Tris lactose supplemented with amylase followed by seminal plasma removal via centrifugation (TL_A__Cent.) and re-suspension into enzyme free TL media. After equilibration, control group recorded 62.85 ± 4.28% motility and 1.3 ± 0.13 viscosity score, while TL_A group values were 72.88 ± 3.30% and 0.83 ± 0.07%, respectively. TL_A__Cent. group showed significant viscosity reduction (0.33 ± 0.05) and motility decline 47.85 ± 3.04% with increment in abnormalities and detached acrosome. The second experiment investigated the effect of caffeine addition to tolerate enzymatic and mechanical stress. Using 4 mM caffeine in amylase-treated semen (TL_AC) improved post-thaw motility 50.0 ± 1.29% and recovery rate 77.8 ± 3.83% compared to the control (40.17 ± 2.79% and 62.55 ± 8.39%), respectively. Caffeine supplemented centrifuged samples (TL_AC__Cent.) showed superiority (P < .05) in post-thaw motility and recovery rate (38.33 ± 6.41%, 62.76 ± 8.10%) compared to centrifuged samples TL_A__Cent. without caffeine addition (25.00 ± 2.88% and 40.47 ± 3.48%), respectively. Sperm kinetics showed that TL_A exhibited high (p < .05) values for mostly all sperm kinetics. Caffeine treatments showed superiority in velocity curved line (VCL, µm/s) 94.24 ± 8.44 for TL_AC and 104.25 ± 8.72 for the TL_AC__Cent. group compared to 86.8 ± 5.54 for TL_A, and 85.73 ± 5.99 for the TL_A__Cent. groups. In conclusion, preforming a combined enzymatic-mechanical protocol in the presence of an antioxidant may be crucial for refinement of camel semen cryopreservation.

The effect of two packaging systems on the post-thaw characteristics of canine sperm

The aim of this study was to compare the effect of different packaging systems on some parameters of cryopreserved canine spermatozoa. The experimental material consisted of the sperm-rich fractions of ejaculates collected from four Beagle dogs. Semen samples for cryopreservation were stored in 0.25 ml plastic straws and two aluminum tubes with a total volume of 5.0 ml. Semen was frozen in static nitrogen vapor for 10 minutes (0.25 ml straws) or 15 and 20 minutes (aluminum tubes). Post-thaw assessments involved the determination of sperm motility parameters using a computer assisted sperm analyzer (CASA), sperm plasma membrane integrity (SPMI), mitochondrial membrane potential (MMP) and acrosome integrity (normal apical ridge, NAR). Regardless of the packaging system applied, no significant differences in total sperm motility (TMOT) or selected kinematic parameters were observed after freezing-thawing. However, spermatozoa frozen in 0.25 mL straws were characterized by improved functionality, in particular mitochondrial function, after thawing. The results indicate that large quantities of canine semen can be frozen in aluminum tubes. Further studies are required, however, to evaluate different freezing and thawing rates of aluminum tubes.

Effects of rapid cooling prior to freezing on the quality of canine cryopreserved spermatozoa

The aim of this study was to evaluate the effects of rapid cooling prior to freezing on frozen-thawed canine sperm quality. In experiment 1, centrifuged ejaculates from 6 dogs were pooled, split into 4 aliquots and cryopreserved by the Uppsala procedure using different cooling rates (control, cooling speed 18 C/90 min and average cooling rate 0.2 C/min; rapid, cooling speed 18 C/8 min and average cooling rate 2.25 C/min) in combination with 2 glycerol addition protocols (fractionated or unfractionated). In experiment 2, centrifuged ejaculates from 4 dogs were processed individually using the same cooling rates described in experiment 1 in combination with an unfractionated glycerol addition protocol. Each of the experiments was replicated 5 times. Sperm quality was evaluated after 30 and 150 min of post-thawing incubation at 38 C. Total motility (TM), progressive motility (PM) and quality of movement parameters were assessed using a computerized system, and sperm viability (spermatozoa with intact plasma and acrosome membranes) was assessed using flow cytometry (H-42/PI/FITC-PNA). Values for TM, PM, viable spermatozoa and the quality of movement parameters after thawing were not significantly affected by the cooling rate. The interaction between the cooling rate and the added glycerol protocol was not significant. There were significant differences among the males (P<0.01) in the sperm quality parameters evaluated after thawing. The interaction between the males and the cooling rate was not significant. In conclusion, canine spermatozoa can be cryopreserved using the Uppsala method at an average cooling rate of 2.25 C/min prior to freezing together with addition of fractionated or unfractionated glycerol.

Cryoprotection effectiveness of low concentrations of natural and lyophilized LDL (low density lipoproteins) on canine spermatozoa

The aim of this study was to evaluate the use of low concentrations of natural and lyophilized low density lipoprotein (LDL) from hen's egg yolk for cryopreservation of canine semen. Different ammonium sulphate concentrations were tested to extract LDL from egg yolk. The yolk was centrifuged, and LDL was isolated using 10, 20, 40, 45, or 50% ammonium sulphate solution (ASS). The LDL-rich floating fraction was collected for chemical characterization. Dry matter content was lowest (P<0.05) in the LDL extracted with the 50% ASS. The purification of LDL increased in association with increasing ammonium sulphate concentrations. SDS-PAGE showed that the 50% ASS solution yielded a purer fraction of LDL from egg yolk. For semen cryopreservation, TRIS extender was used replacing 20% egg yolk (control) by natural or lyophilized LDL using 1, 2, and 3% (w/v). Semen was centrifuged (755Xg for 7 min), diluted with one of the extenders, packed into 0.5mL straws (100x106 sperm/mL), and placed in a programmable cryopreservation machine. Thawed semen (37°C/ 30s) was analyzed for sperm motility, morphology, and by the hypoosmotic and epifluorescence tests (CFDA/ PI). Natural LDL extracted with 50% ASS was as effective as whole egg yolk to preserve canine frozen sperm when using low concentrations. The lyophilized LDL, mainly in the two higher concentrations tested (2 and 3%), was unsuitable to maintain the effectiveness of the LDL cryoprotective effect on dog sperm.

Immunolocalization of the cholesterol transporters ABCA1 and ABCG1 in canine reproductive tract tissues and spermatozoa

The mammalian sperm membrane undergoes cholesterol efflux during maturation and fertilization. Although ATP-binding cassette (ABC) transporters are known to transport cholesterol through cell membranes in other organs, their presence in canine testis, epididymis and sperm has not been proven to date. Hence, the aim of the present study was to localize the ABC transporters ABCA1 and ABCG1 in canine testicular and epididymidal tissue as well as in spermatozoa membranes. To this end, semen samples from 12 dogs as well as testicles and epididymides of four young and healthy dogs were prepared for immunohistochemistry, respectively. Capacitation and acrosome reaction (AR) were induced in aliquots of the semen samples before immunostaining to assess changes in the expression of ABCA1 and ABCG1. Evaluation by confocal microscopy revealed the presence of both ABCA1 and ABCG1 in canine testicles and of ABCA1 in the epididymides. In spermatozoa, only ABCA1 immunoreactivity was detected, mainly in the region of the acrosome and midpiece. After induction of capacitation, ABCA1 signal persisted in the acrosome but disappeared after AR, indicating a loss of ABCA1 with the loss of the acrosome. We conclude that ABCA1 and ABCG1 are expressed in canine testis, whereas only ABCA1 is expressed in epididymis and spermatozoa membrane, both transporters probably contributing to the regulation of membrane cholesterol content.

Cryopreservation of feline epididymal spermatozoa from dead and alive animals and its use in assisted reproduction

Cryopreservation of gametes is an important tool in assisted reproduction programmes; long-term storage of oocytes or spermatozoa is necessary when in vitro fertilization (IVF) or artificial insemination is to be performed at a future date. Cryopreservation of epididymal spermatozoa offers a potential tool for rescuing genetic material from males of endangered populations. The objectives of this work were to: (1) examine sperm motility, viability, abnormality and acrosome integrity of frozen–thawed domestic cat epididymal spermatozoa; and (2) evaluate the same cryopreservation method on wild feline spermatozoa, needed to preserve their genetic resources. Epididymides were collected from 20 domestic cats during routine neutering procedure and from two wild felines at autopsy. The sperm samples, diluted with 4% glycerol/Tris/egg yolk, were loaded into 0.25 ml mini-straws, exposed to nitrogen vapour and stored in liquid nitrogen. After 4 weeks, samples were thawed and re-evaluated. The quality of each fresh and frozen–thawed sperm sample was tested by determining the motility (54.7 ± 11.3% and 32 ± 13.1% respectively for cat spermatozoa; 38.3 ± 18.7% and 21.5 ± 16.8% respectively for tiger spermatozoa), viability (74.3 ± 8.6% and 45.2 ± 9.4% respectively for cat spermatozoa; 42.4 ± 14.5% and 33.5 ± 12.9% respectively for wild felid spermatozoa), morphology and acrosomal status. The present study showed that feline epididymal spermatozoa can be frozen in egg-yolk extender with 4.0% glycerol in 0.25 ml straws. The procedure used in the present study for epididymal cat sperm cryopreservation may be applied to bank the genetic resources of wild felid species.

Trehalose enhanced the freezability of Poodle dog sperm collected by an artificial vagina (AV)

In an attempt to develop a suitable freezing method for Poodle dog sperm, an experiment was conducted to investigate semen collection methods of digital stimulation and an artificial vagina (AV), using Tris and trehalose-egg yolk extender, on the characteristics and cryopreservation of sperm. Two dogs (dogs A and B) were subjected to semen collection by digital stimulation and AV. The volume, sperm concentration, sperm motility index (SMI) and acrosome status of ejaculates were determined immediately after collection. The remainder was frozen as pellets in Tris and trehalose-egg yolk extender. Sperm motility index was evaluated after thawing and during a thermal resistance test, and acrosome integrity was also assessed. No significant differences regarding sperm concentrations, SMI and acrosome integrity were observed between semen collected by AV and digital stimulation. However, when dog sperm were collected by an AV and frozen in trehalose-egg yolk extender, the motility index of frozen-thawed sperm was significantly improved compared to sperm frozen in Tris-egg yolk extender which were collected by digital stimulation. In conclusion, semen collected by an AV and frozen in trehalose-egg yolk extender was effective in enhancing the freezability of Poodle dog sperm.