Effect of N-acetyl-D-glucosamine, and glycerol concentration and equilibration time on acrosome morphology and motility of frozen-thawed boar sperm

A novel experimental design for boar sperm cryopreservation

Cryopreservation of sperm is a routine technology in many livestock species, but not in swine. Frozen sperm must result in acceptable conception rates and produce 11-12 piglets/litter to be competitive with traditional cooled semen. The development of an extender that results in high post-thaw sperm quality and acceptable litter size requires identification of factors that markedly impact post-thaw semen quality. The present study aims to first identify factors in boar sperm cryopreservation that significantly impacts post-thaw sperm quality using an efficient, cost-effective, and relatively rapid approach. The Plackett-Burman experimental design is ideal for the screening of factors at their extreme, greatly reducing the amount of time and resources needed for a follow-up, full factorial design. Using commercial semen, a 9 factor, 12 run Plackett-Burman design was used on 10 boars split between 12 treatments. Via this method glycerol concentration, cooling rate, antioxidant supplementation with GameteGuard(Membrane Protective Technologies, Inc. Fort Collins, CO), and straw size were identified as highly influential factors that impact post-thaw sperm quality. Extender type, starting osmolality, sodium dodecyl sulfate addition, and stepwise addition of glycerol were also influential for some but not all post-thaw sperm parameters (p<0.05). Equilibration time in the straws before freezing was determined to have no impact on post thaw sperm quality parameters. Using the Plackett-Burman design, it can be concluded that four of the nine factors warrant detailed investigation in a full factorial experiments in development of boar sperm cryopreservation extenders.

Interaction among extenders, cryoprotectants and Orvus Es Paste supplementation and freezing rate for sperm cryopreservation in the dromedary camel

This study evaluated the effects of freezing extenders, cryoprotectants and their concentrations, presence of Orvus Es Paste and freezing rates for cryopreserving dromedary camel sperm. Semen (five males; 2 ejaculates/male) was frozen in one of the following extenders (Green Buffer^® or INRA96^® ), cryoprotectants (3 and 6% glycerol or ethylene glycol), with or without Orvus Es Paste and freezing at two different heights (1 and 4 cm) above liquid nitrogen. Sperm motility recovery parameters were evaluated post-thaw (0 and 1 hr), vitality and acrosome integrity (0 hr). Green Buffer showed higher total motility recoveries (p < .001). Higher percentage of cryoprotectant improved both total and progressive motility at 0 hr (p < .001; p = .003) and 1 hr (p < .001; p = .005). Acrosome integrity at thawing increased in the presence of ethylene glycol (p < .001) and Orvus Es Paste (p = .001). Kinematics were affected by extender, cryoprotectant concentration and Orvus Es Paste at 0 and 1 hr, and type of cryoprotectant only influenced them at 0h. Our findings showed strong interactions among type of cryoprotectant and concentration, and extender and Orvus Es Paste. Generally, combining Green Buffer, 3%-6% ethylene glycol or 6% glycerol without Orvus Es Paste, regardless of the freezing rates, yielded the highest post-thaw parameters for camel sperm.

Metabolite Support of Long-Term Storage of Sperm in the Spermatheca of Honeybee (Apis mellifera) Queens

The polyandrous mating system of honeybees (Apis mellifera L.) has garnered widespread attention. Long-lived honeybee queens only mate early in maturation, and the sperm obtained from the aerial mating is stored in the spermatheca. The maintenance of sperm viability in the spermatheca is an intriguing and complex process. However, the key physiological and biochemical adaptations underlying the long-term storage of sperm remain unclear. Analysis of the metabolite profile could help better understand the biology of the spermatheca and offer insights into the breeding and conservation of honeybees and even pest control strategies. Here, the changes in metabolites in the spermatheca were quantified between virgin queens and new-laying queens (with stored sperm) via liquid chromatography-mass spectrometry. Compared with virgin queens, changes occurred in lipids and lipid-like molecules, including fatty acyls and glycerophospholipids (GPL), prenol lipids, and sterol lipids, during storage of sperm in new-laying honeybee queens. Furthermore, the metabolic pathways that were enriched with the differentially expressed metabolites were identified and included GPL metabolism, biosynthesis of amino acids, and the mTOR signaling pathway. The likely roles of the pathways in the maintenance and protection of sperm are discussed. The study identifies key metabolites and pathways in the complex interplay of substances that contribute to the long-term storage of sperm and ultimately reproductive success of honeybee queens.

Effects of different equilibration times at 5 °C on boar sperm cryotolerance

Equilibration time (ET) is the period during which sperm cells are in contact with cooling/freezing media components at a temperature of 5 °C, providing a proper osmotic balance between the intra- and extra-cellular milieu. The present study aimed to determine the ET (0, 2, and 4 h) that results in greater post-thaw sperm quality and functions. Based on the post-thaw sperm membrane integrity and motility ratios, 20 ejaculates collected from five boars were classified as having good (GFE, n = 5) or poor (PFE, n = 15) freezing capacity. Ratios of post-thaw sperm with intact plasma membrane and acrosome were similar between ET (0 h: 37.02 % ± 2.85 %; 2 h: 34.59 % ± 7.12 %; 4 h: 37.87 % ± 4.44 %) in GFE samples. In PFE, ratios of sperm with intact plasma membrane and acrosome at post-thaw were greater (P < 0.05) after an ET of 2 h than after an ET of 0 h (2 h: 26.16 % ± 1.54 % and 0 h: 16.74 % ± 1.59 %). Also, ratios of post-thaw sperm with relatively lesser membrane lipids disorder were greater (P < 0.05) after an ET of 2 h than for other ET in both GFE (2 h: 21.97 % ± 4.24 % and 0 h: 16.63 % ± 2.38 %) and PFE (2 h: 16.65 % ± 1.40 % and 0 h: 13.23 % ± 1.25 %) samples. In conclusion, an ET of 2 h results in greater sperm cryotolerance in both GFE and PFE samples, which suggests that modifying the freezing protocol lead to an increase post-thaw sperm function and survival.

Effect of green tea (Camellia sinensis) extract and pre-freezing equilibration time on the post-thawing quality of ram semen cryopreserved in a soybean lecithin-based extender

The aim of this study was to determine the effect of Camellia sinensis extract as antioxidant supplement and pre-freezing equilibration times in a soybean lecithin extender for freezing ram semen. In this study, a total of 20 ejaculates were collected from four Ghezel rams and diluted with extenders (1.5% soybean lecithin, 7% glycerol) containing no supplements (control) and Camellia sinensis extract (5, 10, and 15 mg/L) and cryopreserved, immediately after thermal equilibrium was reached at 5 °C (0 h), or 4 h after equilibration. Sperm motility characteristics, membrane integrity, abnormal morphology, mitochondria activity, apoptotic status, MDA and antioxidant activities (GPx, SOD and total antioxidant capacity (TAC)) were evaluated following freeze-thawing. Camellia sinensis extract at level 10 mg/L led to the highest total and progressive motilities percentages, in comparison to other treatments (P < 0.05). Our results showed that Camellia sinensis extract at level of 5 and 10 mg/L led to higher plasma membrane integrity, mitochondria activity and Total antioxidant capacity (TAC) in comparison to the level of 15 mg/L and control group (P < 0.05). Camellia sinensis extract at 10 mg/L level produced the highest percentage of live spermatozoa and the lowest apoptotic spermatozoa in comparison to all treatments (P < 0.05). In addition, level of MDA formation significantly decreased at this concentration, 10 mg/L, compared to all treatments (P < 0.05). No differences (P > 0.05) were observed between equilibration times (0 h vs. 4 h) for sperm samples incubated with or without different concentrations of Camellia sinensis extract. In conclusion, addition of Camellia sinensis extract at level of 10 mg/L can improve post-thawing quality of ram semen cryopreserved in a soybean lecithin extender. However, further research is needed to standardize the process of Camellia sinensis extraction and specially for identifying which compounds are responsible of its beneficial effect on ram sperm cryopreservation.

Effect of cooling rate and equilibration time on pre-freeze and post-thaw survival of buck sperm

Survival of buck sperm is affected due to duration and temperature of stages of refrigerated or frozen storage. This study investigated interactive effect of cooling rates (moderate; MC and rapid cooling; RC); and equilibration times (0, 2, 4 and 8h) on survival before freezing at 4°C and post-thaw quality of buck sperm. Semen was collected (three Beetal bucks; replicates=6), pooled and diluted with Tris-citrate extender. Pooled semen samples were subjected to either RC (-2.2°C/min) or MC (-0.3°C/min) from 37°C to 4°C in separate aliquots and further equilibrated at 4°C for 8h. Semen was frozen using standard procedure after completion of each equilibration period i.e. 0, 2, 4 and 8h. Semen was evaluated for motility, viability, plasma membrane integrity (PMI) and normal apical ridge (NAR) before freezing and after thawing. The survival time (time for survival above threshold limit i.e. 60%) at 4°C, of motility and PMI was observed 5 and 6h respectively in RC group while >8h in MC group. Rate of decline (slope) in motility and viability was higher (P<0.05) in RC overtime during equilibration at 4°C while PMI and NAR declined at equal rate in both cooling groups. Post-thaw motility and NAR were higher (P<0.05) in MC when equilibrated for 2-8h while viability and PMI of RC was observed equal to MC group. In conclusion, survival of buck sperm is higher when cooled with moderate rate. However, RC can maintain post-thaw sperm viability and PMI equal to MC when equilibrated for 2-8h. The methods should be explored to maintain motility and NAR during rapid cooling of buck sperm.

Alternative procedures for the cryopreservation of brown bear ejaculates depending on the flexibility of the "in cooling" period (5°C)

The adaptability of cryopreservation protocols for brown bear spermatozoa collected under field conditions and frozen in a nearby laboratory (transported for a few hours) or shipped to a reference laboratory for sex sorting (transported for a few days) was evaluated. Forty-nine electroejaculates from 15 mature brown bears were extended to 100×10(6) sperm/mL in a TES-Tris-Fructose based extender and cryopreserved (-20°C/min to -100°C and stored at -196°C). After thawing, the quality of the seminal samples was assessed for total (TM), progressive (PM) motility and kinetic parameters - by CASA -, and viability (VIAB), viable and non-apoptotic status (YOPRO-), high membrane mitochondrial potential (MIT) and intact acrosomes (iACR) - by flow cytometry -. In Experiment 1, we assessed different storage times (0, 0.5, 1 - control -, 4-5, 7-8 and 11-12 h) at 5°C from final dilution to freezing. After thawing, non-equilibrated samples (0 h) showed lower values of iACR, TM and PM. No significant differences were found for the different periods of equilibration tested. In Experiment 2, we evaluated three long-term storage times (24, 48 and 72 h) at 5°C before freezing using storage for 1h as control. The post-thawing quality of brown bear spermatozoa declined markedly after 48-72 h of pre-freezing. In conclusion, our findings suggest the possibility of extending the pre-freezing cooling period up to 24h post-collection without freezing. This knowledge should enable the adaptation of the freezing protocols for when a special handling conditions are required such as the shipment of seminal samples to technological centers for the pre-freezing application of enhancer spermatic biotechnologies.

Advances in boar semen cryopreservation

The present paper highlights aspects of the cryopreservation of boar semen, a species with particular large, fractionated ejaculates, and a cumbersome cryotechnology that had prevented its commercial application. With the dramatic increase of use of liquid pig semen for artificial breeding over the past decade, developments on cryopreservation alongside the routine use of stud boar semen for AI had been promoted. Recent advances in our laboratory, accommodating the best use of portions of the sperm-rich fraction of the ejaculate for cryopreservation of the sperm-peak portion (P1) and parallel use of the rest of the collected ejaculated spermatozoa, appears as a suitable commercial alternative.