Sperm freezing damage: the role of regulated cell death

Substantial progress in research on sperm cryopreservation has occurred since the twentieth century, especially focusing on improving sperm freezing procedures and optimizing semen extenders. However, the cellular biological mechanisms of sperm freezing damage are still unclear, which greatly restricts the promotion and development of sperm cryopreservation. An essential component of sperm freezing damage is the occurrence of cell death. Considering the existence of multiple types of cell death pathways, this review discusses connections between characteristics of regulated cell death (e.g., apoptosis and ferroptosis), and accidental cell death (e.g., intracellular ice crystals) with sperm freezing damage and explores possible future research directions in this field.

Inhibition of phospholipase C reduces the capacitation of cryopreserved ovine sperm

This study aimed to evaluate the effect of phospholipase C (PLC) on the capacitation of cryopreserved ovine semen. Sixteen semen samples were cryopreserved with diluent added by 0, 10, or 20 μM of U73122, a PLC inhibitor. The sperm kinetics of the thawed samples were evaluated using the "Computer-assisted Sperm Analysis" system, and the integrity of the plasma and mitochondrial membranes was evaluated using fluorescent probes. Additionally, sperm capacitation and the acrosome reaction with chlortetracycline hydrochloride were evaluated before and after capacitation induction. The results were analysed using analysis of variance and Tukey's test with a 95% probability. Concentrations of 10 or 20 μM of U73122 did not affect the kinetics or number of sperm with intact plasma and mitochondrial membranes. However, after thawing, 10 and 20 μM of the inhibitor reduced the percentage of capacitated and acrosome-reacted sperm. After induction of capacitation, there was a reduction in the number of non-capacitated sperm in all treatment groups, suggesting a reversible effect of U73122. In conclusion, U73122 at concentrations of 10 or 20 μM prevents premature capacitation and acrosome reaction induced by the freezing procedure, without affecting the kinetics and integrity of the sperm membranes.

Effects of Different Diluents on Semen Quality of Hu Ram Stored at 4 °C

This study aimed to investigate the effects of various diluents on the quality of Hu ram sperm stored at 4 °C. Semen samples were collected from three Hu rams and diluted with diluents A (Sodium citrate-Glucose-Egg yolk), B (Sodium citrate-Glucose), C (Fructose-Skimmed milk powder-Soy lecithin), and D (Tris-Fructose-Citric acid-Egg yolk). Total motility (TM), straight-line velocity (VSL), average path velocity (VAP), curvilinear velocity (VCL), average motion degree (MAD), acrosome integrity, membrane integrity, and reactive oxygen species (ROS) were evaluated. The results showed that diluent D had better preservation in terms of the sperm TM, VSL, VCL, VAP, MAD, and membrane and acrosome integrity. On the third day of the storage, the sperm PM of diluent D was higher than that of other diluents (p < 0.05). The ROS level of diluent D was lower than that of other diluents on the fifth day (p < 0.05). On the seventh day of the storage, the sperm TM in diluent D reached 50%, which was the highest in all diluent groups. On the seventh day of the storage, the integrity of the sperm membrane and the integrity of the acrosome of the sperm in diluent D were the highest in all diluent groups (p < 0.05). In conclusion, these results indicated that diluent D improved the semen quality during storage at 4 °C. In this study, diluent D was the best diluent formula for Hu ram semen stored at 4 °C.

The Proteomic Modification of Buck Ejaculated Sperm Induced by the Cryopreservation Process

Using two-dimensional electrophoresis along with mass spectroscopy, we have investigated how the cryopreservation process affected the protein profile of goat ejaculated sperm. In this study, five bucks were used for semen collection. After removal of seminal plasma, the Tris-based extender containing glycerol and egg yolk was used to freeze semen. The results indicated that the post-thaw sperm quality showed a significant reduction compared with fresh sperm. The numbers of protein spots acquired in fresh and post-thaw sperm were 2926 ± 57 and 3061 ± 81, respectively. Twenty-two different abundant proteins (DAPs) were identified between fresh sperm and frozen-thawed sperm (≥3.0-folds, p < 0.05). The abundances of 19 proteins were significantly higher in the fresh sperm than the post-thaw sperm. The results of the gene ontology annotation showed the primary location of the DAPs on sperm cytoskeleton, protein complex, cytoplasm, and mitochondria. In addition, these proteins were mainly involved in ion binding, small molecular metabolic processes, structure molecule activity, guanosine triphosphatase activity, oxidoreductase activity, and protein complex assembly. The interaction networks among these DAPs demonstrated that they may play roles in oxidoreductase activity, structure, acrosomal function, and motility of sperm. Collectively, the proteome of goat sperm was altered during the cryopreservation process, demonstrating that protein modification induced by cryopreservation may be associated with the reduced quality of goat sperm after thawing.

Factors Affecting the Survival of Ram Spermatozoa during Liquid Storage and Options for Improvement

Simple Summary

The success of semen preservation is vital for the use of artificial reproductive technologies in sheep. However, reduced temperatures can cause significant damage to the sperm cell. Recent investigations in other species have identified room-temperature liquid storage as a viable alternative if spermatozoa are protected from the increased risk of lipid peroxidation, a side effect of unaltered metabolism. The following review aims to summarise the factors which contribute to the survival of ram spermatozoa during liquid storage and the role of pro-survival factors and antioxidants in helping to ameliorate the damaging effects caused by lipid peroxidation on fertility. This would contribute towards establishing a new method of semen preservation for the sheep industry which maximises fertility following storage and artificial insemination.

Abstract

Semen preservation is an essential component of reproductive technologies, as it promotes genetic gain and long-distance semen transport and multiplies the number of ewes able to be inseminated per single ejaculate. However, the reduced temperature during cold storage at 5 or 15 °C inflicts sub-lethal damage to spermatozoa, compromising sperm quality and the success of artificial breeding. New and emerging research in various species has reported the advantages of storing spermatozoa at higher temperatures, such as 23 °C; however, this topic has not been thoroughly investigated for ram spermatozoa. Despite the success of storing spermatozoa at 23 °C, sperm quality can be compromised by the damaging effects of lipid peroxidation, more commonly when metabolism is left unaltered during 23 °C storage. Additionally, given the biosafety concern surrounding the international transport of egg-yolk-containing extenders, further investigation is critical to assess the preservation ability of synthetic extenders and whether pro-survival factors could be supplemented to maximise sperm survival during storage at 23 °C.

Implications of cryopreservation on structural and functional attributes of bovine spermatozoa: An overview

Sperm cryopreservation is an important adjunct to assisted reproduction techniques (ART) for improving the reproductive efficiency of dairy cattle and buffaloes. Improved understanding of mechanisms and challenges of bovine semen cryopreservation is vital for artificial insemination on a commercial basis. Although cryopreservation of bovine spermatozoa is widely practiced and advanced beyond that of other species, there are still major gaps in the knowledge and technology. Upon cryopreservation, disruption of spermatozoal plasma membrane configuration due to alterations in metabolic pathways, enzymes and antioxidants activity add to lower efficiency with loss of sperm longevity and fertilising ability. Therefore, the effective amalgamation of cryo-variables like ambient temperature, cooling and thawing rates, nucleation temperature, type and concentration of the cryoprotectant, seminal plasma composition, free radicals and antioxidant status are required to optimise cryopreservation. Novel strategies like supplementation of cholesterol-loaded cyclodextrins (CLC), nanovesicles, osteopontin, antioxidants, etc., in an extender and recent techniques like nano-purification and modified packaging have to be optimised to ameliorate the cryodamage. This article is intended to describe the basic facts about the sperm cryopreservation process in bovine and the associated biochemical, biophysical, ultra-structural, molecular and functional alterations.

The proteomic characterization of ram sperm during cryopreservation analyzed by the two-dimensional electrophoresis coupled with mass spectrometry

The aim of this study was to analyze the effects of the cryopreservation process on the protein profile of ram sperm using two-dimensional electrophoresis (2-DE) coupled with mass spectroscopy. Semen was collected from five rams and cryopreserved in a Tris-based extender supplemented with glycerol and egg yolk as the main cryoprotectants. The fresh and post-thaw sperm total proteins were extracted and purified, followed by the 2-DE. The differential proteins in the stained gel were determined by mass spectrometry. The results indicated that there were 39 differential proteins between fresh sperm and frozen-thawed sperm. Among these proteins, the abundance of 28 proteins in fresh sperm was higher than those in post-thaw sperm (P < 0.05). However, 11 proteins in post-thaw sperm were up-regulated instead. The gene ontology (GO) analysis showed that most of differential proteins were implicated in cellular process, metabolism and regulation of the biological process. The networks of protein-protein interaction indicated a strong interaction among these differential proteins, which may be involved in sperm metabolism, acrosomal function, sperm motility, and reducing ROS level. In conclusion, the cryopreservation process modifies the proteome of ram sperm, which may be directly associated with ram sperm cryodamage, consequently influencing their fertility. Additionally, these differential proteins can be used as biomarkers for evaluation of frozen ram semen quality.

The role of environmental optimization for storing bulls' sperm cells

Artificial insemination has achieved a dynamic increase in genetic progress, and this is due to the improvement of sperm preservation technology. In recent years, a lot of attention has been paid to optimizing bull sperm storage environment and objectifying methods of sperm quality analysis. This review presents bull sperm preservation methods and ways to modify their storage environment. The main purpose of sperm preparation for artificial insemination is to obtain sperm with a high percentage of viable, motile sperm with normal morphology and low DNA fragmentation rates. Currently conducted experiments indicate the possibility of improving the quality of insemination doses produced using various components enriching common diluents. However, despite extensive research, no better results have been achieved than obtaining insemination doses with sperm viability that exceeds just over 60%. Obtaining a very good quality of frozen semen seems to be still unachievable today.

Pre-freezing equilibration for 22 h improves post-thaw sperm functions in cryopreserved ram semen by reducing cholesterol efflux

Failure of cervical insemination with cryopreserved semen is hindering implementation of AI in sheep in field condition. Here the effect of equilibration time and catalase on post-thaw qualities of ram semen was investigated. Pooled semen was diluted (800 × 10⁶ sperm mL^-1) with a TES-Tris-fructose extender with 6% glycerol, 15% egg yolk and supplemented with 0, 50, 100 and 200 U mL^-1 catalase and packaged into 0.25 mL straws. In experiment 1, straws were equilibrated at 5 °C either for 3 h in a cold cabinet (E3) or for 10 (E10) and 22 h (E22) inside a refrigerator. In experiment 2, all straws were equilibrated for 22 h inside refrigerator. Straws were frozen at -25 °C min^-1 up to -125 °C using a cell freezer and finally plunged into liquid nitrogen. The post-thaw total and rapid motility were higher (P < 0.05) in E22 compared to E3 and E10. Sperm kinetics was comparable between E3 and E22, but lower in E10. Similarly, acrosome integrity, functional membrane integrity, percent high cholesterol (mCHO) and live-high mitochondrial membrane potential (MMP) were higher (P < 0.05) while live-high intracellular calcium and acrosome-reacted sperm were lower in E22 compared to E3 and E10. The percent rapid motile, high mCHO and live-high MMP were significantly (P < 0.05) lower in catalase-treated samples compared to the control, while the membrane integrity was comparable within the groups. In conclusion, pre-freezing equilibration for 22 h compared to 3 or 10 h resulted in higher post-thaw sperm functions while catalase had negative impact on cryopreservation of ram semen.

Directional freezing of spermatozoa and embryos

Directional freezing is based on a simple thermodynamic principle whereby the sample is moved through a predetermined temperature gradient at a velocity that determines the cooling rate. Directional freezing permits a precise and uniform cooling rate in small- and large-volume samples. It avoids supercooling and reduces mechanical damage caused by crystallisation. Directional solidification was used to date for slow and rapid freezing, as well as for vitrification of oocytes and embryos by means of the minimum drop size technique: small drops are placed on a microscope slide that is moved at high velocity from the hot base to the cold base. Sperm samples from a wide range of domestic and wild animals were successfully cryopreserved using the directional freezing method. The bovine sexed semen industry may benefit from the increased survival of spermatozoa after directional freezing.

Changeability of sperm chromatin structure during liquid storage of ovine semen in milk-egg yolk- and soybean lecithin-based extenders and their relationships to field-fertility

The aim of this experiment was to study the effect of semen extender on sperm chromatin structure and to correlate chromatin integrity with field-fertility of preserved ram semen. Ejaculates of at least 2 × 10(9) sperm/ml and 70 % progressive motility were collected using an artificial vagina from Chios rams (n = 11, 4-6 years old), split-diluted to 1 × 10(9) sperm/ml with milk-egg yolk- and soybean lecithin (Ovixcell®)-based extenders, packaged in 0.5-ml straws and examined after 6, 24 and 48 h of storage at 5 ± 1 °C. Evaluation endpoints were computer-assisted sperm motion analysis, fluorescence-based analysis of chromatin structure by chromomycin A3 and acridine orange assays, and 65-day pregnancy rate (PR) of 34- to 36-h preserved semen after intra-cervical insemination of ewes (n = 154) in progestagen-synchronized estrus. Neither extender nor storage time had any influence on incidence of decondensed chromatin. Unlike Ovixcell® extender, deterioration of sperm motility (P < 0.01) and chromatin stability (P < 0.005) was detected after 48 h of storage in milk-egg yolk extender. Sperm motility accounted for 14.4-18.5 % of variations in chromatin integrity (P < 0.001). No significant difference was found in PR of Ovixcell®- and milk-egg yolk-stored semen. Nevertheless, PR differed between rams (14.3-71.4 %; P < 0.025). Chromatin integrity explained 10.2-56.3 % of variations in PR (P < 0.05-0.01). A pronounced decline in PR (19.1 %) was observed when percentages of decondensed and destabilized chromatin have reached thresholds of 10.5-30 % and 4-9 %, respectively. In conclusion, Ovixcell® is superior to milk-egg yolk extender in preserving chromatin stability and motility. Chromatin defects are negatively associated with sperm fertility.

Association of soybean-based extenders with field fertility of stored ram (Ovis aries) semen: a randomized double-blind parallel group design

Two consecutive randomized double-blind field fertility experiments were conducted over a 4-month period and aimed at evaluating the association of two commercial soybean lecithin-based extenders (AndroMed [Minitub, Tiefenbach, Germany] and BioXcell [IMV Technologies, L'Aigle, France]) with pregnancy rates of chilled-stored (CS) and frozen-thawed (FT) ram semen. Semen samples with more than 2 × 10(9) sperm per mL and 70% progressive motile spermatozoa were collected via an artificial vagina from twelve proven fertile Chios rams, split-diluted with the above mentioned extenders, packaged in 0.25 mL straws and either stored at 5 ± 1 °C for 30 to 36 hours or frozen and thawed. Non-lactating multiparous ewes were inseminated in progestagen-synchronized estrus either with CS (AndroMed: N = 212 and BioXcell: N = 206; intracervical AI) or with FT (AndroMed: N = 114 and BioXcell: N = 92; laparoscopic intrauterine AI) semen. Ovulation was confirmed in all ewes based on determination of blood plasma progesterone (>1 ng/mL) 8 days post AI. Ewes were screened for pregnancy diagnosis by transabdominal ultrasonography 65 days post AI. BioXcell was superior to AndroMed in preserving the fertilizing potential of CS (P < 0.05) and FT (P < 0.005) semen. In AndroMed-stored semen, young rams (1.5-2.5 years old, N = 8) had a pregnancy rate (59.1%; 124/210) lower than that (72.4%; 84/116) of mature rams (4.5 to 5.5 years, N = 4; P < 0.025). Compared with AndroMed extender, processing of young ram semen in BioXcell extender improved pregnancy rates of CS (66.7%; 88/132 vs. 83.9%; 94/112; P < 0.005) and FT (46.2%; 36/78 vs. 71.0%; 44/62; P < 0.01) spermatozoa. Both extenders were similarly effective in preserving pregnancy rates of mature ram semen (P > 0.05). Ram-by-extender interactions were significant for pregnancy rates of CS and FT semen. Irrespective of extenders, overall pregnancy rates after intracervical and intrauterine AI were 75.1% and 62.2%, respectively (P < 0.001). In conclusion, BioXcell is a suitable extender for short- and long-term storage of ram semen. Selection of the ewes, farms, and extenders for intracervical AI programs can contribute to satisfactory fertility rates with semen preserved more than 24 hours at 5 °C.

Artificial insemination of small ruminants - a review

Artificial insemination (AI) can undoubtedly be regarded as the oldest and most widely used assisted reproductive technique/technology (ART) applied in livestock production and it is one of the most important ARTs. The three cornerstones of its application are that it is simple, economical and successful. Artificial insemination offers many well-known benefits for producers. Fresh, fresh + diluted + chilled and frozen semen can be used for AI in small ruminants. To ensure its successful use, the AI technique must be selected on the basis of the type of semen planned to be used. This review paper gives a detailed overview of semen processing and its effects on semen quality, as well as of the AI techniques applied in small ruminants and their success rates.

Effect of controlled and uncontrolled cooling rate on motility parameters of cryopreserved ram spermatozoa

Background

Ram spermatozoa are sensitive to extreme changes in temperature during the freeze-thaw process. The degree of damage depends on a combined effect of various factors including freezing temperature. The aim of this study was to determine the effects of two cooling method (controlled-rate and uncontrolled-rate) on pre-freezing and post-thaw sperm motility parameters.

Results

Ejaculates were collected using the artificial vagina from four Chal rams and three replicates of the ejaculates were diluted with a Tris-based extender and packed in 0.25 ml straws. Then, sample processed according to the two methods. Method 1: straws cooled from 37 to 5°C, at a liner rate of -0.3°C/min in a controlled-rate cooling machine (custom-built) and equilibrated at 5°C for 80 min, then the straws were frozen at rate of -0.3°C/min from 5°C to -10°C and -25°C/min from -10°C to -150°C and plunged into liquid nitrogen for storage. Method 2: straws were transferred to refrigerator and maintained at 5°C for 3 h, then the straws were frozen in liquid nitrogen vapor, 4 cm above the liquid nitrogen for 15 min and plunged into liquid nitrogen. Computer-assisted sperm motility analysis was used to analyze sperm motion characteristics.

Conclusions

Controlled rate of freezing (Method 1) significantly improve the pre-freezing and post-thaw total and progressive motility compared to uncontrolled rate (Method 2). In specific kinetic parameters, Method 1 gives significantly higher value for VSL and VCL in comparison with Method 2. There are no significant differences between the two methods for VAP and LIN. In conclusion, controlled rate of cooling conferred better cryopreserving ability to ram spermatozoa compared to uncontrolled rate of cooling prior to programmable freezing.

Comparison of prostaglandin- and progesterone-based protocols for timed artificial insemination in sheep

The objective was to compare the reproductive performance of a new PGF(2α)-based timed artificial insemination (TAI) protocol in sheep (Synchrovine®: two doses of PGF(2α), 7 d apart) to a traditional progesterone-eCG (P4-eCG) protocol, considering the effects of seminal state, AI-times, and AI-pathway. Three experiments involving 1297 multiparous Australian Merino ewes were done during the physiologic breeding season (location 32 °S-57 °W). Reproductive performance was assessed as non-return rate to service 21 d after AI (NRR21d), based on detection with androgenized wethers, as well as Fertility (pregnant/inseminated ewes), Prolificacy (fetuses/pregnant ewe), and Fecundity (fetuses/inseminated ewe), which were based on transabdominal ultrasonography 50 d after TAI. In Experiment 1, Synchrovine® treated ewes TAI cervically with fresh semen at 42, 48, or 54 h had similar NRR21d (0.51, 0.46, 0.57), Fertility (0.27, 0.31, 0.26), and Fecundity (0.29, 0.32, 0.27), all of which were lower (P < 0.05) than in a control P4-eCG group inseminated at 54 h (0.61, 0.48, 0.52, NRR21d, Fertility and Fecundity respectively). In Experiment 2, using chilled semen and cervical TAI, Synchrovine® treated ewes inseminated at 42 h yielded lower (P < 0.05) NRR21d, Fertility and Fecundity (0.28, 0.06, 0.06) compared to 48 (0.43, 0.24, 0.24) and 54 h (0.44, 0.22, 0.23). In Experiment 3 with chilled semen, Synchrovine® treated ewes TAI into the cervix at 51 or 57 h were similar in NRR21d (0.16 vs 0.20), Fertility (0.12 vs 0.14), and Fecundity (0.12 vs 0.15), respectively; but lower (P < 0.05) than P4-eCG treated ewes TAI at 54 h (0.34, 0.28, and 0.33 for NRR21d, Fertility and Fecundity respectively). Synchrovine® treated ewes intrauterine TAI at 51 or 57 h yielded similar NRR21d (0.51 vs 0.58), Fertility (0.43 vs 0.51), and Fecundity (0.45 vs 0.56) respectively, but lower (P < 0.05) results compared to P4-eCG treated ewes (0.75, 0.71, and 0.88 for NRR21d, Fertility and Fecundity respectively). In conclusion, AI-time in Synchrovine® treated ewes with fresh semen might be extended (42 to 54 h after the second PGF(2α)), but should be delayed to 48-54 h with chilled semen and cervical AI. Independent of the seminal state, AI-time or AI-pathway, Synchrovine® yielded lower reproductive results than a conventional P4-eCG protocol.

Alterations of domains in the plasmatic membrane due to damages of the perinuclear theca of pig preserved spermatozoa

Samples of semen from 12 pigs, three from Yorkshire, Landrace, Duroc and Mexican Hairless each where obtained to study cryopreservation methods. Three stages of boar semen cryopreservation were evaluated: none (fresh stage), cooling at 5 degrees C and freezing at -196 degrees C then thawing to 56 degrees C for 12 sec. Perinuclear theca damage and domain alterations were selected as indices of seminal quality, as measured by electronic and fluorescence microcopy, respectively according to two lineal models considering by separately the effect of semen preservation and breed. Integrity and absence of perinuclear theca significantly (p < 0.001) decreased and increased, respectively according to a decrease in temperature of cryopreservation, from 87.4 to 58.8% and from 0.8 to 26.2%, respectively. This same significant (p < 0.001) effect was found for acrosomal and post-acrosomal membrane distribution of domains, from 92.1 to 76.8% and from 3.1 to 13.1% in this same order. Slight but highly significant (p < 0.001) differences were observed when theca integrity was evaluated as affected by breed, with highest and lowest values for Yorkshire and Pel6n Mexicano pigs, respectively. No breed effect was encountered for presence of acrosomal domains. A strong interdependence was found between perinuclear theca damage and domain distribution. In this connection, a highly significant (p < 0.001) positive, interdependence was observed between the theca damage and acrosomal domain (r = 0.87), while this same relationship was although highly significant (p < 0.001), negative in nature for equatorial and post-acrosonal domains (r = -0.77 and -0.85, respectively). This experiment confirmed that cryopreservation methods may severely affect semen quality of pigs and that genotype may further influence these same indices. More research is needed for improving methods of preservation of pig semen quality, from the point of view of perinuclear theca and domain characteristics of spermatozoa.

Resuspending ram spermatozoa in seminal plasma after cryopreservation does not improve pregnancy rate in cervically inseminated ewes

The role of seminal plasma (SP) components on the maintenance of motility, viability and fertilising ability of frozen-thawed spermatozoa is of considerable interest. However, differences observed in constituents of SP among males could explain differences in fertility obtained in vivo. Two experiments were designed to examine the effects of seminal plasma on fertility from cervically inseminated frozen-thawed semen. The objective of Experiment 1 was to investigate if source or type of SP influences pregnancy rate. Seminal plasma was collected from rams previously classified as having either High (HSP; n=3) or Low (LSP; n=3) fertility in vivo. Artificial SP (fructose/sodium solution with 10% BSA; ASP) was made. Frozen semen from the same 6 rams was thawed and inseminated (Control) or resuspended either in HSP, LSP or ASP (20% in semen) prior to insemination of ewes (n=284, over 2 farms). The overall pregnancy rate was 28.1%. Treatments (Control, ASP, HSP and LSP) were not significantly different (P>0.3). There was no difference between HSP and LSP (P>0.5), and no effect of using ASP compared to ram SP (P>0.7), on pregnancy rate. As there was no effect of SP on pregnancy rate a repeat experiment (Experiment 2) was designed to test the effect of washing and selecting motile sperm prior to resuspending in phosphate-buffered saline (PBS) containing SP on pregnancy rate. Frozen-thawed semen from each of 2 rams was centrifuged through a density gradient, pellets were centrifuged through a wash medium and the sperm concentration/ram was counted. Sperm cells were resuspended in: (1) control PBS, (2) PBS containing 30% HSP or (3) PBS containing 30% LSP to give 100 x 10(6) motile sperm in 0.25 mL. Control straws were thawed and inseminated directly. Ewes (n=223 over 2 farms) were inseminated 57 h post-sponge withdrawal and those not returning to oestrus were slaughtered 29-50 days post-insemination for pregnancy determination. In Experiment 2, the pregnancy rate for Control, PBS, HSP and LSP were 15.4%, 2.3%, 0% and 0%, respectively, for Farm 1 (P>0.05) and 17.8%, 11.0%, 3.9% and 12.4%, respectively, for Farm 2. Under the conditions of the current study, addition of SP from different donors of either High or Low fertility status to frozen-thawed ram semen post-thawing did not improve pregnancy rate in ewes. ASP had no effect on pregnancy rate in ewes when added to frozen-thawed semen. Washing and selection of motile sperm prior to resuspension in PBS with or without SP (30%) before insemination had a negative effect on pregnancy rate in cervically inseminated ewes. Hence, the addition of seminal plasma or some of its constituents to semen does not appear to improve pregnancy rate in cervically inseminated ewes.