Simple and economic colloidal centrifugation protocols may be incorporated into the clinical equine sperm processing procedure

Strategies to Reduce the Use of Antibiotics in Fresh and Chilled Equine Semen

The study assessed the impact of four equine semen processing techniques on sperm quality and microbial load immediately post-processing and after 48 h of refrigeration. The aim was to explore the potential reduction of prophylactic antibiotic usage in semen extenders. Semen from ten adult stallions was collected and processed under a strict hygiene protocol and divided into four aliquots: Simple Centrifugation with antibiotics (SC+), Simple Centrifugation (SC-), Single-Layer Colloidal Centrifugation (CC-), and Filtration (with SpermFilter®) (F-), all in extenders without antibiotics. Sperm motility, viability, and microbial load on three culture media were assessed. No significant differences were observed in the main in the sperm quality parameters among the four protocols post-processing and at 48 h (p < 0.05 or p < 0.1). Microbial loads in Columbia 5% Sheep Blood Agar and Schaedler vitamin K1 5% Sheep Blood Agar mediums were significantly higher (p < 0.10) for raw semen than for CS+, CC-, and F- post-processing. For Sabouraud Dextrose Agar medium, the microbial load was significantly higher (p < 0.10) in raw semen compared to CS+ and F-. No significant differences (p < 0.10) were found in 48 h chilled samples. Regardless of antibiotic presence, the evaluated processing methods, when combined with rigorous hygiene measures, maintained semen quality and reduced microbial load to the same extent as a traditional protocol using antibiotics.

Optimization of the Equine-Sperm Freeze Test in Purebred Spanish Horses by Incorporating Colloidal Centrifugation

The Purebred Spanish Horse, according to our clinical experience, is characterized by having a high number of stallions that do not meet the international commercial recommendations for equine-sperm cryopreservation. This means that artificial insemination with frozen semen from these stallions is less widespread than in other breeds. In this study, we investigated if the incorporation of single-layer colloidal centrifugation prior to cryopreservation in clinical conditions could increase the number of ejaculates of Purebred Spanish stallions suitable for this processing, observing the influence of centrifugation and freezing extender protocol on post-thawed sperm motility. Using colloidal centrifugation, the percentage of ejaculates available to be frozen was increased from 35% (6/17) to 71% (12/17), doubling the number of samples that could have been subjected to cryopreservation. We only found significant differences in linearity (LIN) and lateral head displacement (ALH) after 5 min of incubation at 37 °C between colloidal and simple centrifugation processing techniques. No significant differences were found between the two different colloidal protocols in any of the variables considered. Colloidal centrifugation allowed us to obtain, from worse fresh-quality ejaculates, thawed sperm doses with similar quality to that of good-quality ejaculates. BotuCrio^® produced, in general, higher motility parameters and its characteristics than the other extenders analyzed, with significant differences found in comparison to Inra-Freeze^® and Lac-Edta in both total (MOT) and progressive motility (PMOT) when using colloidal centrifugation and only in PMOT when applying simple centrifugation. Colloidal centrifugation optimized the efficiency of cryopreservation, as it allowed us to increase the number of ejaculates of Purebred Spanish Horses suitable to be frozen. Including these semen processing techniques in the freeze test could help to optimize equine-sperm cryopreservation protocols, especially when dealing with individuals or breeds for which initially low sperm quality prevents or limits their inclusion in sperm cryopreservation programs.

Stallion sperm selection prior to freezing using a modified colloid swim-up procedure without centrifugation

The aims of this study were to: 1) develop a new method for stallion sperm selection using a modified swim-up procedure through a colloid and 2) evaluate its impact in good quality ejaculates from bad freezers in comparison to methods involving centrifugation such as single layer centrifugation and sperm washing. Ejaculates were processed before freezing using three different procedures: sperm washing (SW), colloid single layer centrifugation (SLC) and a modified colloid swim-up (SU). After semen processing, sperm recovery rates were measured and sperm were frozen. Post-thaw sperm motility (assessed by computer-assisted sperm analysis), normal forms and plasma membrane integrity (evaluated under bright-field and fluorescence microscopy respectively), and DNA fragmentation (assessed by the Sperm-Halomax kit) were compared between treatments. Sperm recovery rates were similar between SU and SLC but lower than SW. Sperm motility after thawing was lower in SU in comparison to SLC and SW, maybe due to the incomplete removal of seminal plasma before freezing. Sperm DNA fragmentation was lower in SU and SLC selection methods, particularly in SLC selected samples during the first 6h of incubation. The remaining sperm parameters assessed were similar among treatments. In conclusion, SLC is more suitable than SW and SU to process stallion semen prior to freezing, in particular when sperm DNA damage is suspected. Further studies are needed in order to determine the potential benefits of SU in samples where centrifugation is not necessary, such as epididymal sperm, ejaculate fractioning or post-thaw semen samples.

Kinematic and spermatic recovery after selection by centrifugation in colloid solutions of ovine cryopreserved semen

ABSTRACT Frozen and thawed ovine semen undergo morphological and functional changes that prevent or decrease the efficiency of fertilization. Sperm selection methods seek to improve the quality and viability of the fertilizing materials. Four sperm selection methods were employed, using two silica colloidal solutions coated with silane (silica colloidal-silane) or by polyvinylpyrrolidone (silica colloidal-PVP), and varying the volume of colloidal solution. Sperm kinematic and sperm recovery were evaluated by means of CASA. The protocols using silica colloidal-silane showed higher total motility (TM), progressive motility (PM) and percentage of rapid sperm (%RAP) compared to the methods employing silica colloidal-PVP and to the samples prior to sperm selection. The silica colloidal-PVP had greater sperm recovery compared to the silica colloidal-silane. Only the method using 4mL of silica colloidal-PVP was not efficient in selecting samples with better quality compared to the samples analyzed prior to sperm selection. The methods using lower volumes of colloidal solution did not differ from those using higher volumes and the best results were shown by the method with 1mL silica colloidal-silane. The results found in the study indicated greater efficiency of the silica colloidal-silane solution for sperm selection of thawed ovine semen when compared to selection using silica colloidal-PVP. The method using 1mL of silica colloidal-silane was equally efficient to the method with higher volume, presenting itself as an alternative to process samples with lower sperm concentration.

Advances in Stallion Semen Cryopreservation

The use of stallion frozen semen minimizes the spread of disease, eliminates geographic barriers, and preserves the genetic material of the animal for an unlimited time. Significant progress on the frozen thawed stallion semen process and consequently fertility has been achieved over the last decade. These improvements not only increased fertility rates but also allowed cryopreservation of semen from "poor freezers." This article reviews traditional steps and new strategies for stallion semen handling and processing that are performed to overcome the deleterious effects of semen preservation and consequently improve frozen semen quality and fertility.

Use of density centrifugation for delayed cryopreservation of stallion sperm: perform sperm selection directly after collection or after storage?

Equipment for cryopreservation of stallion sperm is not always available. In such cases, diluted semen can be shipped to a facility for later cryopreservation. The aim of this study was to evaluate if selection of sperm via density centrifugation yields higher survival rates when cryopreservation is to be delayed (i.e. carried out after 1 day of storage at 5°C). Two-layer iodixanol as well as single-layer Androcoll density centrifugation were tested and compared with samples prepared with standard centrifugation. Special emphasis was placed on comparing centrifugation on the day of semen collection with centrifugation after 1-day refrigerated storage. Sperm morphology and motility as well as membrane and chromatin integrity were evaluated before and after centrifugation. Sperm motility and membrane integrity were also assessed after cryopreservation. It was found that both two- and single-layer density centrifugation processing resulted in higher percentages of morphologically normal and motile sperm with higher membrane and chromatin integrity, as compared to standard centrifugation or diluted samples. Differences were only in the order of magnitude of 5%. Recovery rates after density centrifugation were only approximately 30-40%. When cryopreservation was carried out after 1-day refrigerated storage, centrifugation processing of sperm directly after semen collection resulted in higher percentages of plasma membrane intact sperm post-thaw as compared to performing centrifugation processing of stored sperm just prior to cryopreservation. No significant differences in progressively motile sperm post-thaw were seen. Taken together, for delayed cryopreservation, it is best to perform density centrifugation directly after collection rather than immediately prior to cryopreservation.

Dense spermatozoa in stallion ejaculates contain lower concentrations of mRNAs encoding the sperm specific calcium channel 1, ornithine decarboxylase antizyme 3, aromatase, and estrogen receptor alpha than less dense spermatozoa

Stallions are unique among livestock in that, like men, they commonly receive medical treatment for subfertility. In both species, about 15% of individuals have normal semen parameters but are subfertile, indicating a need for novel analyses of spermatozoa function. One procedure for improving fertilizing capability of stallions and men is isolation of dense spermatozoa from an ejaculate for use in artificial insemination. In the current study, dense and less dense spermatozoa were purified by density gradient centrifugation from individual ejaculates from seven reproductively normal adult stallions. The RNA isolated from the spermatozoa seemed to be naturally fragmented to an average length of 250 bases, consistent with reports of spermatozoa RNA from other species. The DNAse treatment of RNA prepared from spermatozoa removed any genomic DNA contamination, as assessed by PCR with intron spanning primers for the protamine 1 (PRM1) gene. Concentrations of seven mRNAs in spermatozoa, correlated with the fertility of men and bulls, were quantified by reverse transcription polymerase chain reaction in dense and less dense spermatozoa. Concentrations of four mRNAs were two- to four-fold lower in dense spermatozoa compared with less dense spermatozoa: Encoding the spermatozoa-specific calcium channel (P < 0.03), ornithine decarboxylase antizyme 3 (P < 0.02), aromatase (P < 0.02), and estrogen receptor alpha (P < 0.08). In contrast, concentrations of three other mRNAs, encoding PRM1 and heat shock proteins HSPA8 and DNAJC4, were not different (P > 0.1). These results identify new differences in mRNA concentrations in populations of spermatozoa with dissimilar densities.

The effect of two pre-cryopreservation single layer colloidal centrifugation protocols in combination with different freezing extenders on the fragmentation dynamics of thawed equine sperm DNA

Background

Variability among stallions in terms of semen cryopreservation quality renders it difficult to arrive at a standardized cryopreservation method. Different extenders and processing techniques (such us colloidal centrifugation) are used in order to optimize post-thaw sperm quality. Sperm chromatin integrity analysis is an effective tool for assessing such quality. The aim of the present study was to compare the effect of two single layer colloidal centrifugation protocols (prior to cryopreservation) in combination with three commercial freezing extenders on the post-thaw chromatin integrity of equine sperm samples at different post-thaw incubation (37°C) times (i.e., their DNA fragmentation dynamics).

Results

Post-thaw DNA fragmentation levels in semen samples subjected to either of the colloidal centrifugation protocols were significantly lower (p<0.05) immediately after thawing and after 4 h of incubation at 37°C compared to samples that underwent standard (control) centrifugation. The use of InraFreeze® extender was associated with significantly less DNA fragmentation than the use of Botu-Crio® extender at 6 h of incubation, and than the use of either Botu-Crio® or Gent® extender at 24 h of incubation (p<0.05).

Conclusions

These results suggest that single layer colloidal centrifugation performed with extended or raw semen prior to cryopreservation reduces DNA fragmentation during the first four hours after thawing. Further studies are needed to determine the influence of freezing extenders on equine sperm DNA fragmentation dynamics.

Assessment of sperm function parameters and DNA fragmentation in ejaculated alpaca sperm (Lama pacos) by flow cytometry

Flow cytometry has been shown to be an accurate and highly reproducible tool for the analysis of sperm function. The main objective of this study was to assess sperm function parameters in ejaculated alpaca sperm by flow cytometry. Semen samples were collected from six alpaca males and processed for flow cytometric analysis of sperm viability and plasma membrane integrity using SYBR-14⁄PI staining; acrosomal membrane integrity using FITC-conjugated Pisum Sativum Agglutinin⁄PI labelling; mitochondrial membrane potential (Δψm) by staining with JC-1 and DNA Fragmentation Index (DFI) by TUNEL. The results indicate that the mean value for sperm viability was 57 ± 8 %. Spermatozoa with intact acrosome membrane was 87.9 ± 5%, and viable sperm with intact acrosomal membrane was 46.8 ± 9%, high mitochondrial membrane potential (Δψm) was detected in 66.32 ± 9.51% of spermatozoa and mean DFI value was 0.91 ± 0.9%. The DFI was inversely correlated with high Δψm (p = 0.04; r = -0.41) and with plasma membrane integrity (p = 0.01; r = -0.47). To our knowledge, this is the first report of the assessment on the same sample of several parameters of sperm function in ejaculated alpaca sperm by flow cytometry.

Sperm selection using single layer centrifugation prior to cryopreservation can increase thawed sperm quality in stallions

REASONS FOR PERFORMING STUDY

The increasing use of modern reproductive techniques in human medicine has led to a higher demand for isolation of motile sperm. Several of these isolation techniques have been adapted for veterinary use and can be applied for the selection of a superior sperm sample from stallion semen. Until recently a major disadvantage of such isolation techniques was the limitation in sperm volume that could be handled. Androcoll-E had been shown to be successful for processing large volumes of equine semen but there are few data to substantiate the potential beneficial effect of freezing an Androcoll-E selected equine sperm sample to obtain higher quality following thawing.

OBJECTIVES AND METHODS

In this study, the effect of Androcoll-E treatment of sperm prior to cryopreservation was compared with cushioned centrifugation using ejaculates from 8 different stallions selected because they were known to have semen of differing quality following freezing.

RESULTS

Androcoll-E treatment increased measures of semen quality prior to freezing. However, Androcoll-E treatment reduced the yield of sperm following centrifugation when compared with the cushion centrifuged control group (50.9 ± 14.2% vs. 97.1 ± 9.0%, respectively). Quality analysis following thawing showed an overall improved sperm quality for Androcoll-E treated samples and average post thaw progressive motility (PM) was 41.6% compared with 30.5% for the cushion centrifuged group.

CONCLUSIONS AND POTENTIAL RELEVANCE

Androcoll-E can be used with good results to select a superior sperm population prior to cryopreservation, in order to produce good-quality frozen thawed semen.