Preservation of fowl semen in liquid nitrogen: application to breeding programmes

Exploring how sucrose-colloid selection improves the fertilizing ability of chicken sperm after cryopreservation with glycerol

Currently, glycerol is the most effective cryoprotectant when combined with straw packaging for preserving chicken sperm. Glycerol, however, has toxic effects on sperm cells, which can reduce fertility when present in inseminated semen. Historically, the serial dilution (SD) method was developed to eliminate glycerol and mitigate its adverse effects. We have recently developed a new method for removing glycerol called sucrose-Percoll (SP), that can be performed at either 4°C (4°C-SP) or 20°C (20°C-SP). This SP protocol has been found to be simpler and faster to improve fertility compared to the traditional SD method. Nevertheless, the reasons for such effectiveness differences between glycerol removal procedures remained unclear and required more comprehensive understandings for future protocol developments. Here, we examined the effects of SP and SD protocols on the fertility duration. We also investigated the potential causes of varying effects of these methods by analyzing sperm quality parameters and sperm storage in the hen's reproductive tract. The fertility was significantly higher in 4°C-SP than 20°C-SP during the first 6 d after insemination, and also higher than sperm processed using SD. No difference was observed between 20°C-SP and SD between 7 and 13 d. However, a 2.7-time higher fertility was shown with 4°C-SP. In addition, the SP method demonstrated a 2-fold greater ability to remove glycerol than the SD method. Sperm centrifuged at 4°C-SP exhibited higher sperm storage compared to 20°C-SP and were higher than sperm treated with SD. Overall, our findings revealed that the differences in efficiencies between SP and SD methods were not related to in vitro sperm quality but resulted from a higher ability to remove glycerol, a higher storage capacity in the female reproductive tract, and a longer fertility ability. Since no impacts were observed in sperm cellular characteristics, further experiments are necessary to investigate the influences of glycerol removal treatments at the molecular level.

A simple and fast alternative method to remove glycerol from chicken semen after cryopreservation

A concentration of 11% of glycerol is the standard one for sperm cryopreservation in chickens, however, the presence of just 2% glycerol already causes severe fertility reduction, suggesting the necessity of removing glycerol before artificial insemination (AI). The major approach developed for this purpose is serial dilution followed by centrifugation (SDC), which demands special equipment (such as a refrigerate room) to maintain post-thaw semen at 4 °C, besides being time consuming. Therefore, we attempted to develop a simple method to remove glycerol from chicken frozen-thawed semen based on a colloidal gel, Percoll, which is ordinarily used to select motile and viable sperm in mammals as well as in fresh chicken semen. In this study, we used a Percoll based glycerol removal solution (GRS) containing sucrose to avoid frozen-thawed sperm suffering from osmotic stress. Subsequently, several conditions including GRS compositions (GRS A, B, C and D) and centrifugation temperatures (4 and 20 °C) were compared by their influence on sperm in vitro parameters. Afterwards, GRS A and D were selected for fertility evaluation, compared to conventional SDC method. Our results showed that the fertility with GRS A at both 4 and 20 °C were higher than GRS D (p < 0.05) and similar or even superior to the fertility obtained with SDC method. Altogether, our novel GRS protocol is a valuable method for chicken sperm cryobanking policy, supported by its notable results of fertility as well as saving 44% of time, with a simple equipment at flexible operation temperatures of 4 or 20 °C.

Freezing chicken semen: Influence of base medium osmolality, cryoprotectants, cryoprotectant concentration, and cooling rate on post-thaw sperm survival

A classical chicken semen diluent (Lake's 7.1 diluent) was modified to have lowered osmolalities (ranging from 290-410 mOsm/kg). The modified medium with physiological osmolality of 325 mOsm/kg allowed cold storage of fresh semen for several days with very little loss of membrane integrity and motility, while high osmolalities inhibited motility. This modified medium was then used as base for freezing medium to test effects of the type and concentration of cryoprotective agent (CPA), and the cooling rate (CR). A number of CPAs (methylformamide, methylacetamide, dimethylformamide (DMF), dimethylacetamide (DMA), diethylformamide, and propylene glycol) were first compared by freezing semen with 0.6 mol/l of the respective CPA at a cooling rate of 250°C/min. Post-thaw motility and membrane integrity were highest with DMA and DMF. Finally, in more detailed factorial experiments, semen from individual cocks or pooled semen was frozen using CRs of 4, 50, 250, and 440 °C/min and DMA concentrations ([DMA]) of 0.4, 0.6, 1.0, and 1.5 mol/l. Straws from each semen sample x treatment combination were divided for semen assessment at three different research groups for sperm motility, membrane integrity, kinked tails, and DNA fragmentation, using microscopy, computer assisted motility analysis, and flow cytometry. There were clear effects of both CR and [DMA] and their interaction. CRs 50 and 250°C/min gave best post-thaw sperm performance. Higher DMA concentrations gave better post-thaw membrane integrity, but concentrations above 1.0 mol/l can decrease sperm velocity or even inhibit sperm motility. Therefore [DMA] may best be 0.6-1.0 mol/l at a CR of 50-250°C/min.

From the Semen Collection Method to the Hatchlings: The Use of Cryopreserved Sperm from Pheasants Fed an Antioxidant-Enriched Diet

A widely used approach to preserving genetic diversity in birds involves the cryopreservation of semen. In this process, cells are subjected to physical and chemical stresses, but not all cell species respond equally. Many studies have been published on the freezing-thawing of sperm cells from a wide variety of domestic and wild species, on issues ranging from the sperm quality to different protocols, fertilisation success rates, etc. Nevertheless, very little information is available on the common pheasant. To fill this gap, the aim of this study was to describe the pheasant semen collection method, evaluate some qualitative parameters of sperm from males fed an antioxidant-enriched diet, and to test the in vivo fertilising capacity of the cryo-preserved semen. The freezing protocol employed involved pellets thawed by the hotplate method. Dimethylacetamide was used as a cryoprotectant at a final concentration of 6%. A total of six AIs were performed at 3-4-day intervals on a total of 40 females with doses of 35 × 106 of normal live thawed sperm. Males receiving the enriched diet produce more abundant and concentrated ejaculates. Freeze-thawed sperm lost 85% of their initial mobility, and diet influenced neither sperm mobility nor viability. The enriched diet did improve the number of normal freeze-thawed cells and was associated with a lower sperm fracture incidence. Regardless of the dietary group, frozen-thawed sperm resulted in a fertility rate of 30%, with 8-9 chicks hatching for every 100 eggs incubated.

Cryopreservation of Avian Semen

Cryopreservation protocols for semen exist for bird species used in animal production, fancy and hobby species, and wild bird species. Freezing of bird oocytes or embryos is not possible. Cryopreservation of avian semen is used for preserving (genetic diversity of) endangered species or breeds. Freezing semen can also be used in the breeding industry for maintaining breeding lines, as a cost-effective alternative to holding live birds. Success and efficiency of cryopreservation of bird semen differs among species and breeds or selection lines. This chapter describes important variables of methods for collecting, diluting, cold storage, and freezing and thawing of bird semen, notably the medium composition, cryoprotectant used and its concentration, cooling rate, freezing method, and warming method. Media and methods are described for freezing semen using either glycerol or DMA as cryoprotectant, which both are known in chicken and a number of other bird species to render adequate post-thaw fertility rates.

Effect of N-Methylacetamide Concentration and Thawing Rate on Chicken Sperm Quality after Cryopreservation

Simple Summary

The semen cryopreservation technology is still the only efficient method for the ex situ conservation of genetic diversity in birds. This study investigates the effect of different concentrations (6% and 9%) of the cryoprotectant N-Methylacetamide and of different thawing temperatures (at 5 °C for 100 s; 38 °C for 30 s) on chicken semen quality after cryopreservation. The cryoprotectant concentration significantly affected sperm membrane integrity, total and progressive motility after cryopreservation and this effect was dependent by the thawing temperature. The treatment that provided the best cryoprotective action and decreased the cellular cryodamage was the concomitant use of 6% N-Methylacetamide and thawing at 5 °C for 100 s. These results can contribute to improve the efficacy of the current chicken semen cryopreservation technology.

Abstract

In seeking alternative cryoprotectants to glycerol for a reference chicken semen freezing procedure, the aim of the present study was to compare the effect of two concentrations of N-Methylacetamide (MA) and two thawing rates on the quality of frozen-thawed semen. Semen samples were diluted in Lake pre-freezing extender, including 0.1 M trehalose in presence of 6% or 9% MA, loaded into straws, frozen in nitrogen vapors, and stored in liquid nitrogen. The following thawing treatments were used: 5 °C for 100 s and 38 °C for 30 s. Sperm quality (cell membrane integrity, motility and kinetic parameters) was assessed before and after cryopreservation. The decrease of MA concentration from 9 to 6% improved sperm quality after freezing/thawing and this effect was dependent on thawing temperature. Decreasing the MA concentration from 9 to 6% improved the proportion of undamaged membrane, motile, and progressive motile sperm recovered after thawing at 5 °C for 100 s; in contrast, no effect of the MA concentration was observed thawing at 38 °C for 30 s. Therefore, the treatment with 6% MA and thawing at 5 °C for 100 s has given the best cryoprotective action. These results contribute to improve the efficacy of the current chicken semen cryopreservation procedures.

Effect of dimethylacetamide and N-methylacetamide on the quality and fertility of frozen/thawed chicken semen

The aim was to compare the effect of dimethylacetamide (DMA) and N-methylacetamide (NMA) concentrations on the quality and fertility of post-thaw chicken semen. Ejaculates were obtained from 30 Hi-Line White roosters and processed according to the following treatments: lake pre-freezing extender + 0.1 M trehalose (LPF-T) + 6% DMA (control treatment), LPF-T + 9% DMA, LPF-T + 6% NMA, and LPF-T + 9% NMA. Sperm quality (viability, motility, and kinetic traits) was assessed before and after cryopreservation. A total of 15 laying hens per treatment were inseminated to assess fertility and embryo viability. Sperm cryopreserved in presence of DMA had significantly better in vitro quality compared to NMA, showing the highest proportion of viable and progressive motile sperm recovered after thawing. Furthermore, proportion of progressive motile sperm and the VCL, LIN, ALH, and WOB mean values were significantly improved in semen samples frozen/thawed with 6% compared to 9% cryoprotectant concentration. However, the best cryoprotective action on sperm quality played by DMA and the lowest cryoprotectant concentration did not translate into a concomitant advantage in in vivo semen fertility that showed no differences between cryoprotectant and cryoprotectant concentration treatments. Finally, the cryoprotectant DMA and NMA showed an opposite effect on embryo viability in comparison with the effect played on in vitro semen quality, being NMA more efficient than DMA on preserving viable embryos. The present results suggest the urgency to further decrease the cryoprotectant concentration in poultry semen freezing procedures and to assess the specific toxic effect of cryoprotectant on sperm integrity, fertility, and embryo development.

New insights in the AMPK regulation in chicken spermatozoa: Role of direct AMPK activator and relationship between AMPK and PKA pathways

Energy balance is an important feature for spermatozoa functions. The 5'-AMP-activated protein kinase (AMPK), a sensor of cell energy, has been implicated as a mediator between spermatozoa functions and energy balance. We recently identified and localized the AMPK protein in chicken spermatozoa and showed that its activation with non-specific activators significantly modified spermatozoa quality. The aim of the present study was to determine more directly the role of AMPK activation induced by the specific activator A-769662 and the interaction between AMPK and another pathway, the protein kinase A (PKA) signaling pathway in bird spermatozoa. The results showed that A-769662 induced at the low dose 50 μM an increase in spermatozoa motility, viability, and acrosome reaction through AMPK activation. Furthermore, phospho-Thr172-AMPK levels were greatly decreased by the PKA inhibitor H89 that also decreased spermatozoa quality. The inhibitory action of H89 was also efficient on A-769662 AMPK phosphorylation. We conclude that AMPK activity in bird spermatozoa is stimulated by low dose of A-769662 with consequent increase in spermatozoa quality, and that AMPK is upstream regulated by PKA pathway in this model.

Avian Biotechnology

Primordial germ cells (PGCs) generate new individuals through differentiation, maturation and fertilization. This means that the manipulation of PGCs is directly linked to the manipulation of individuals, making PGCs attractive target cells in the animal biotechnology field. A unique biological property of avian PGCs is that they circulate temporarily in the vasculature during early development, and this allows us to access and manipulate avian germ lines. Following the development of a technique for transplantation, PGCs have become central to avian biotechnology, in contrast to the use of embryo manipulation and subsequent transfer to foster mothers, as in mammalian biotechnology. Today, avian PGC transplantation combined with recent advanced manipulation techniques, including cell purification, cryopreservation, depletion, and long-term culture in vitro, have enabled the establishment of genetically modified poultry lines and ex-situ conservation of poultry genetic resources. This chapter introduces the principles, history, and procedures of producing avian germline chimeras by transplantation of PGCs, and the current status of avian germline modification as well as germplasm cryopreservation. Other fundamental avian reproductive technologies are described, including artificial insemination and embryo culture, and perspectives of industrial applications in agriculture and pharmacy are considered, including poultry productivity improvement, egg modification, disease resistance impairment and poultry gene "pharming" as well as gene banking.

Calcium channels in chicken sperm regulate motility and the acrosome reaction

Intracellular cytoplasmic calcium ([Ca(2+) ]i ) has an important regulatory role in gamete functions. However, the biochemical components involved in Ca(2+) transport are still unknown in birds, an animal class that has lost functional sperm-specific CatSper channels. Here, we provide evidence for the presence and expression of various Ca(2+) channels in chicken sperm, including high voltage-activated channels (L and R types), the store-operated Ca(2+) channel (SOC) component Orai1, the transient receptor potential channel (TRPC1) and inositol-1,4,5-trisphosphate receptors (IP3 R1). L- and R-type channels were mainly localized in the acrosome and the midpiece, and T-type channels were not detected in chicken sperm. Orai1 was found in all compartments, but with a weak, diffuse signal in the flagellum. TRCP1 was mainly localized in the acrosome and the midpiece, but a weak diffuse signal was also observed in the nucleus and the flagellum. IP3 R1 was mainly detected in the nucleus. The L-type channel inhibitor nifedipine, the R-type channel inhibitor SNX-482 and the SOC inhibitors MRS-1845, 2-APB and YM-58483 decreased [Ca(2+) ]i sperm motility and acrosome reaction capability, with the SOC inhibitors inhibiting these functions most efficiently. Furthermore, we showed that Ca(2+) -mediated induction of AMP-activated protein kinase (AMPK) phosphorylation was blocked by SOC inhibition. Our identification of important regulators of Ca(2+) signaling in avian sperm suggests that SOCs play a predominant role in gamete function, whereas T-type channels may not be involved. In addition, Ca(2+) entry via SOCs appears to be the most likely pathway for AMPK activation and energy-requiring sperm functions such as motility and the acrosome reaction.

Ca2+/Calmodulin-Dependent Protein Kinase Kinases (CaMKKs) Effects on AMP-Activated Protein Kinase (AMPK) Regulation of Chicken Sperm Functions

Sperm require high levels of energy to ensure motility and acrosome reaction (AR) accomplishment. The AMP-activated protein kinase (AMPK) has been demonstrated to be strongly involved in the control of these properties. We address here the question of the potential role of calcium mobilization on AMPK activation and function in chicken sperm through the Ca²⁺/calmodulin-dependent protein kinase kinases (CaMKKs) mediated pathway. The presence of CaMKKs and their substrates CaMKI and CaMKIV was evaluated by western-blotting and indirect immunofluorescence. Sperm were incubated in presence or absence of extracellular Ca²⁺, or of CaMKKs inhibitor (STO-609). Phosphorylations of AMPK, CaMKI, and CaMKIV, as well as sperm functions were evaluated. We demonstrate the presence of both CaMKKs (α and β), CaMKI and CaMKIV in chicken sperm. CaMKKα and CaMKI were localized in the acrosome, the midpiece, and at much lower fluorescence in the flagellum, whereas CaMKKβ was mostly localized in the flagellum and much less in the midpiece and the acrosome. CaMKIV was only present in the flagellum. The presence of extracellular calcium induced an increase in kinases phosphorylation and sperm activity. STO-609 reduced AMPK phosphorylation in the presence of extracellular Ca²⁺ but not in its absence. STO-609 did not affect CaMKIV phosphorylation but decreased CaMKI phosphorylation and this inhibition was quicker in the presence of extracellular Ca²⁺ than in its absence. STO-609 efficiently inhibited sperm motility and AR, both in the presence and absence of extracellular Ca²⁺. Our results show for the first time the presence of CaMKKs (α and β) and one of its substrate, CaMKI in different subcellular compartments in germ cells, as well as the changes in the AMPK regulation pathway, sperm motility and AR related to Ca²⁺ entry in sperm through the Ca²⁺/CaM/CaMKKs/CaMKI pathway. The Ca²⁺/CaMKKs/AMPK pathway is activated only under conditions of extracellular Ca²⁺ entry in the cells.

Fertilisation of cryopreserved sperm and unfertilised quail ovum by intracytoplasmic sperm injection

Intracytoplasmic sperm injection (ICSI) is an important technique in animal biotechnology for animal cloning and conservation of genetic resources, but has been a challenge for avian species. In the present study, we investigated the ability of cryopreserved quail spermatozoa to achieve fertilisation and embryo development. Female quail were killed 70–120 min after previous oviposition to collect unfertilised oocytes from the oviduct. Fresh or cryopreserved–thawed spermatozoa were injected into the cytoplasm of unfertilised oocytes, and the manipulated oocytes were incubated in quail surrogate eggshells. Injection of fresh spermatozoa supplemented with inositol 1,4,5-trisphosphate (IP3) resulted in a significantly increased rate of embryo development compared with injection of fresh spermatozoa alone (90% vs 13%, respectively). Although >80% of embryos stopped cell division and development before Hamburger and Hamilton (HH) Stage 3, approximately 15% of embryos from the fresh sperm injection developed to past HH Stage 4, and one embryo survived up to HH Stage 39 (11 days of incubation). In the case of cryopreserved spermatozoa, the embryo development rate was 30% after ICSI, and this increased significantly to 74% with IP3 supplementation. In conclusion, cryopreserved spermatozoa combined with ICSI followed by surrogate eggshell culture can develop quail embryos.

The 5'-AMP-Activated Protein Kinase (AMPK) Is Involved in the Augmentation of Antioxidant Defenses in Cryopreserved Chicken Sperm

Semen cryopreservation is a unique tool for the management of animal genetic diversity. However, the freeze-thaw process causes biochemical and physical alterations which make difficult the restoration of sperm energy-dependent functions needed for fertilization. 5'-AMP activated protein kinase (AMPK) is a key sensor and regulator of intracellular energy metabolism. Mitochondria functions are known to be severely affected during sperm cryopreservation with deleterious oxidative and peroxidative effects leading to cell integrity and functions damages. The aim of this study was thus to examine the role of AMPK on the peroxidation/antioxidant enzymes defense system in frozen-thawed sperm and its consequences on sperm functions. Chicken semen was diluted in media supplemented with or without AMPK activators (AICAR or Metformin [MET]) or inhibitor (Compound C [CC]) and then cryopreserved. AMPKα phosphorylation, antioxidant enzymes activities, mitochondrial potential, ATP, citrate, viability, acrosome reaction ability (AR) and various motility parameters were negatively affected by the freeze-thaw process while reactive oxygen species (ROS) production, lipid peroxidation (LPO) and lactate concentration were dramatically increased. AICAR partially restored superoxide dismutase (SOD), Glutathione Peroxidase (GPx) and Glutathione Reductase (GR), increased ATP, citrate, and lactate concentration and subsequently decreased the ROS and LPO (malondialdehyde) in frozen-thawed semen. Motility parameters were increased (i.e., + 23% for motility, + 34% for rapid sperm) as well as AR (+ 100%). MET had similar effects as AICAR except that catalase activity was restored and that ATP and mitochondrial potential were further decreased. CC showed effects opposite to AICAR on SOD, ROS, LPO and AR and motility parameters. Taken together, our results strongly suggest that, upon freeze-thaw process, AMPK stimulated intracellular anti-oxidative defense enzymes through ATP regulation, thus reducing ROS and lipid peroxidation, and consequently partially restoring several essential sperm functions and leading to a better quality of cryopreserved sperm.

Sperm-egg penetration assay assessment of the contraceptive effects of glycerol and egg yolk in rooster sperm diluents

Glycerol (GLY) and egg yolk (EY) are good cryoprotectants of avian and mammalian sperm, but in birds, they strongly inhibit the eventual fertilization of ova. Using the sperm penetration (SP-holes) assay and fertility trials, the present study investigates (1) the possible mechanism by which this contraceptive effect occurs in chickens and (2) the maximum concentrations of GLY and EY tolerated by fresh rooster sperm. Seventy Black-Barred Andaluza hens (five per treatment) were inseminated four times (twice per week) with 0.1 mL of fresh semen from roosters of the same breed diluted 1:1 (v:v) with Lake and Ravie medium containing different concentrations of GLY or EY. No adverse effects on acrosome integrity, sperm motility, or viability were seen with any concentration of GLY or EY. The number of SP-holes on perivitelline layer samples taken from above the germinal disc became progressively lower at GLY concentrations of 1.5% or greater (P > 0.05). No holes caused by sperms were seen in unfertilized eggs. The corresponding fertility results showed similar reductions when the GLY concentration was 1.5% or greater. No changes in the number of SP-holes were seen with increasing EY concentrations (0%-7.5%), nor were any differences in fertility observed, except for a reduction when 15% EY was used. The results therefore reveal that GLY affects the transit of sperms through the oviduct in their attempt to reach the infundibulum area, limiting their access to the ovum perivitelline layer. Egg yolk had no such effect, nor did it influence acrosome reaction capacity; its mechanism of contraceptive action therefore remains unknown. The maximum GLY and EY concentrations tolerated by the rooster sperm were 0.75% and 7.5%, respectively.

Central role of 5'-AMP-activated protein kinase in chicken sperm functions

Avian gametes present specific features related to their internal long-term mode of fertilization. Among other central actors of energetic metabolism control, it has been suspected that 5'-AMP-activated protein kinase (AMPK) influences sperm functions and thus plays a key role in fertilization success. In the present work, we studied AMPK localization and function in chicken sperm incubated in vitro. Effects of the pharmacological AMPK activators (AICAR, metformin) and the AMPK inhibitor compound C were assessed by evaluating AMPKalpha (Thr(172)) phosphorylation (by Western blotting), semen quality (by viability, motility, and ability to perform acrosome reaction), and energetic metabolism indicators (lactate, ATP). Localization of AMPK in subcellular sperm compartments was evaluated by immunocytochemistry. Total AMPK was found in all compartments except for the nucleus, but the phosphorylated form phospho-Thr(172)-AMPK was essentially localized in the flagellum and acrosome. AMPK activators significantly improved AMPK phosphorylation, sperm motility (increased by 40% motile, 90% progressive, and 60% rapid sperm), acrosome reaction and lactate production (increased by 40%) and viability. The AMPK inhibitor significantly reduced AMPK phosphorylation and percentages of motility (decrease by 25%), progressive energy (decrease by 35%), and rapid sperm (decreased by 30%), acrosome reaction, lactate production, and ATP release. The two activators differed in their effect on ATP concentration: AICAR stimulated ATP formation, whereas metformin did not. Our results indicate that AMPK plays a key role in the regulation of chicken sperm functions and metabolism. This action differs from that suggested in mammals, mainly by its crucial involvement in the acrosome reaction process.

An efficient method of guinea fowl sperm cryopreservation

France is the only country that practices pedigree selection of guinea fowl for meat production. The increasing risk of line extinction for sanitary or breeding failure reasons makes clear the need for an efficient method of reproductive cell cryopreservation in this species. However, an efficient method of guinea fowl sperm freezing in secured packaging is still lacking. The aim of the present study was to develop such a method. Based on results previously obtained in chickens, different cryoprotectants and freezing/thawing processes were tested and then adapted to guinea fowl. Semen quality was measured by semen viability evaluation and then by fertility measured after intravaginal artificial insemination. The best results (70% fertility with frozen-thawed sperm) were obtained by the use of the permeant cryoprotectant agents dimethyl formamide combined with a freezing rate of 30°C/min. The initial insemination frequency also affected the fertility results: 2 consecutive days of inseminations were needed in the first week to ensure enough filling of the utero-vaginal glands of the guinea fowl hen and thus to get successive fertile eggs. Thereafter, a 2-wk insemination frequency was sufficient. This new method, combining biophysical (cryoprotectant agents, freeze/thaw rate) and zootechnical (artificial insemination frequency) features, is the first cryopreservation method successfully developed in secured packaging for guinea fowl sperm. This method is now available for the practice of gene bank conservation and male reproductive management.

Survival of emu (Dromaius novaehollandiae) sperm preserved at subzero temperatures and different cryoprotectant concentrations

Three experiments were conducted to optimize the protocol for cryopreservation of emu sperm. Ejaculates were collected from trained male emus then diluted 1:1 and pooled before allocation to treatments and measured for sperm viability, motility, egg membrane penetration ability, membrane stability, and morphology. In Experiment 1, semen was either cooled to 5 °C after dilution or diluted with a precooled to 5 °C diluent before cooling to 5 °C and then frozen at liquid nitrogen vapor temperatures of -140 °C and -35 °C, with 6% or 9% dimethylacetmide (DMA; a permeating cryoprotectant) and compared for sperm functions. The percentages of viable (42.8 ± 1.1%), normal (39.0 ± 1.3%), and motile (29.8 ± 1.3%) sperm were higher (P < 0.001) for semen frozen at -14 °C with 9% DMA (path 2) than for all other combinations. In Experiment 2, we assessed the value of combining DMA and trehalose in the diluent. Combining trehalose (3% to 9%) with DMA (3% to 9%) prior to freezing reduced (P < 0.001) the percentages of postthaw viable (by 4 to 9 ± 1.2%), normal (by 5 to 11 ± 1.3%), and motile sperm (by 13 to 17 ± 2.5%) and the number of holes on the perivitelline layer (by 27 to 29 holes/mm(2)). Postthaw function was best preserved with 9% DMA alone. In experiment 3, we investigated the possibility of increasing DMA concentrations from 6% to 24%. Postthaw sperm viability (52 to 55 ± 2.3%) and morphology (48 to 51 ± 1.7%) were higher (P < 0.05) with 18% and 24% than with 6% to 12% DMA and did not differ between 18% and 24% DMA. However, sperm motility (36 to 43 ± 2.9%) and the number of perivitelline holes were similar (P > 0.05) for 9% to 18% DMA (36 to 55 ± 12%). We concluded that adding 6% to 9% trehalose to the diluent offered no advantage, and that the current best practice for preserving postthaw function in emu sperm is to dilute semen with a precooled to 5 °C diluent and use 18% DMA.

Cryopreservation of poultry semen: a review

Although still in the experimental phase, the technique of freezing domestic fowl semen may prove of interest and value to the industry. Various stages of the application of this method of preservation still need to be improved. One of the most critical aspects is the choice of cryoprotectant and its use during the process of freezing and thawing. While glycerol has a better cryopreservative action than other cryoprotectants in domestic fowl semen, it exerts a widely demonstrated contraceptive action, the mechanism of which has not yet been clarified. Thus the use of glycerol as a cryoprotectant must be accompanied by its complete removal before insemination.

The fertilizing capacity of semen preserved by freezing is notably less than that of fresh (non-preserved) material and has been evaluated as 1.6% and 19.7%. Genetic influences appear to affect spermatozoan response and tolerance to thermal treatments resulting in differences in subsequent fertility. Most studies using fowl semen report final freezing temperatures between –79°C and –196°C, a cooling rate of 1–10°C/minute and a thawing rate of 50–70°C/minute.

Straws have been found to be more satisfactory containers than glass vials or ampoules for preserving semen from domestic fowl.

An effective method for improving the fertility of glycerol-exposed poultry semen

Semen cryopreservation is necessary for banking germplasm from critical poultry stocks. To date, glycerol is the most effective cryoprotectant for poultry sperm; however, the contraceptive effects of glycerol require a significant reduction of the cryoprotectant from thawed semen before artificial insemination (AI). The effectiveness of glycerol reduction by dialysis, Percoll density gradient centrifugation, or washing through 12% (wt/vol) Accudenz was evaluated by fertility trials with highly inbred chicken research lines and commercial turkey lines. Semen was extended 1:1 and then diluted with glycerolized extender to yield a final 11% (vol/vol) glycerol concentration. Glycerolized rooster semen was aliquoted for control, Accudenz centrifugation, and dialysis treatments. A total of 90 pure line and 85 F1 hybrid chicken hens were each inseminated with 100 x 10(6) sperm at 7-d intervals for 4 to 6 wk. All eggs from the glycerolized control semen treatments were infertile, and fertility rates from dialyzed semen decreased steadily from 26.4 to 0% within the first 4 wk for the pure lines. In contrast, fertility rates for Accudenz-processed semen increased from 17.9 to 37.17% during the first 4 wk. Similar fertility rates occurred with the F1 hybrid cross lines. For turkey fertility trials, the dialysis treatment was not used; glycerolized turkey semen was processed by Accudenz or Percoll centrifugation to reduce glycerol. A total of 36 hens were inseminated with 150 x 10(6) sperm at 7-d intervals for 6 wk. Similar to the chicken trials, fertility rates of Accudenz-processed semen steadily increased to 49.4% by the sixth week of insemination. The average fertility of Percoll-processed semen was only 19.1%. These data demonstrate that Accudenz centrifugation is an acceptable glycerol reduction method for nonfrozen poultry semen.

Cryopreservation of semen from endangered pheasants: the first step towards a cryobank for endangered avian species

In order to improve the genetic management of bird species within the European Endangered Programs (EEP), a research project on artificial insemination and cryopreservation of Galliformes semen has been developed. The aim of the program is to create a sperm cryobank for threatened bird species. During this study, semen was collected from 17 pheasant species and specific characteristics of ejaculates were analyzed (volume, sperm concentration, motility, pH). Artificial insemination with fresh semen was performed in nine species and with frozen semen in eight species. Inseminations with frozen and thawed semen were made in 17 species. Viability of fresh and frozen semen was assessed in vitro using double stains, eosin and nigrosin. The effect of pH (7-8.5) on viability of fresh and frozen/thawed spermatozoa was also studied. Chicks hatched in eight and three species after insemination with fresh and frozen/thawed semen, respectively. Species varied widely in semen viability: 1-30% of spermatozoa survived freezing and thawing. There was a negative correlation between the viability of frozen spermatozoa and semen pH. In our experimental conditions, the pH of diluents had no effect on semen viability. However, semen with the highest pH had the lowest quality after freezing and thawing. These experiments demonstrated the feasibility of using a very simple and inexpensive method to achieve artificial insemination and cryopreservation of semen in endangered pheasant species.

Cryopreservation of gander semen

1. The effect of dimethylacetamide (DMA) and dimethyl sulphoxide (DMSO) on the cryopreservation of gander semen were investigated. An improved survival rate of spermatozoa after freeze-thawing was obtained when semen was frozen by a fast-freezing procedure on dry ice with 9% DMA as the cryoprotectant. 2. Gander semen, which was frozen during mid season, was tested for fertilising ability in different times of the season. The percentage of fertility during d 3 to d 9 after 2 consecutive inseminations was 68% to 95%, depending on the date of artificial insemination.

DMF effects on frozen gander semen

1. The objective of the present study was to determine if the age of semen donors affects the susceptibility of spermatozoa to freezing and whether DMF (dimethyl formamide) inseminated with freeze-thawed gander semen decreases fertility. 2. Semen was collected 3 times a week by dorsal-abdominal massage from two groups of White Italian ganders: 3 and 2 years-old. Both samples were diluted, mixed with DMF to a final concentration of 6% (v/v), pre-frozen and transferred into LN2. 3. Twice a week, the freeze-thawed semen was used for insemination of two groups of geese at a dose of 4 to 16 million live morphologically normal spermatozoa. One group was inseminated immediately after thawing, the 2nd with semen from which the DMF was removed. 4. Donor age had no effect on the spermatozoa's aptitude for freezing. The differences in quality and quantity of fresh and freeze-thawed semen produced by 3 or 2 year-old ganders were not significant. 5. The presence of DMF in the inseminated freeze-thawed semen did not affect the reproductive efficiency of spermatozoa. The fertility rate obtained with semen inseminated either with or without the cryoprotectant averaged 92.9% and 87.2% respectively. The hatchability of set eggs was 81.1% and 79.9% and, the hatchability of fertile eggs amounted to 87.3% and 89.4%.

Storage of poultry semen

Methods of semen collection and artificial insemination (AI) in poultry, requirement for diluents, methods of liquid and frozen storage of avian semen and evaluation of spermatozoa after storage for fertilizing ability are reviewed. Frozen storage of semen from non-domestic birds is also briefly discussed.

Comparison of cryoprotectants and methods of cryopreservation of fowl spermatozoa

The deleterious effects of three cryoprotectants, glycerol, dimethylsulfoxide (DMSO), and dimethylacetamide (DMA), were compared on fowl spermatozoa. The viability and integrity of spermatozoa were measured with eosin-nigrosin smears. Glycerol was the least deleterious cryoprotectant, followed by DMA, and DMSO was the most toxic. Methods employing either glycerol or DMA were then compared for the cryopreservation of semen in either straws or pellets. Fertility was measured following artificial insemination. The highest fertility rates were obtained with semen frozen with DMA in pellets directly plunged in liquid nitrogen, DMA being added at -6 C (92.7%) or 5 C (84.7%). When semen was frozen in straws, glycerol equilibrated for 1 or 30 min gave the highest fertility results, but the fertility rates were lower (53.7 and 63.9%) than with DMA in pellets. The lowest results (26.7%) were obtained when semen was frozen in straws with DMA. When semen was frozen in pellets at very high cooling rates, DMA was superior to glycerol as a cryoprotectant, as evidenced by fertility. In contrast, when straws and low freezing rates were used, glycerol gave better results; however these results were never as high as those obtained with DMA and pellets. In conclusion, under our experimental conditions, the highest fertility rates were achieved with DMA and pellets. However, for gene banking, which requires high levels of safety and clear identification, glycerol and straws are more convenient.

Measuring sperm:egg interaction to assess breeding efficiency in chickens and turkeys

Systems used to measure fertility in poultry have themselves presented a major impediment to progress in maintaining or improving fertility. Generally, these systems have been time-consuming, quantitatively inadequate, or both. A simplistic illustration of the basis of the problem is that if six fertile eggs were laid by a turkey hen during 1 wk after insemination, then all we know is what happened to six sperm: they fertilized the eggs. If 100 million sperm were inseminated, then information on the other 999,999,994 is missing. A better approach for quantitating breeding efficiency is to estimate the numbers of sperm that interact with the egg in the infundibulum. These can be identified in laid eggs, as sperm in the outer perivitelline layer (OPVL sperm), or holes produced by sperm in the inner perivitelline layer (IPVL holes). Eggs can contain up to 250,000 OPVL sperm, so the scale improves on binary estimation of fertilization status. The number of spermatozoa interacting with the perivitelline layer is related to the artificial insemination (AI) dose, the number of oviducal sperm, and the probability of fertilization, not just for one egg, but for subsequent eggs laid by the same hen. Practical applications of sperm:egg interaction measurements include: replacement of fertility trials for evaluation of semen; general fertility evaluation; and monitoring breeding efficiency of commercial turkey and broiler breeders. Furthermore, studies of sperm transfer into eggs raise interesting questions about the efficiency of turkey hens' response to AI or mating frequency of broiler hens in commercial flocks.

The effect of removing surface-associated proteins from viable chicken spermatozoa on sperm function in vivo and in vitro

When chicken spermatozoa were diluted in isotonic or hypertonic solutions, sperm surface-associated proteins were lost to the medium, quantitatively more protein being lost to medium of higher osmotic strength. The proteins which were removed from the spermatozoa were also found within chicken seminal plasma, but at different relative concentrations, thus demonstrating selective association of only certain seminal proteins with the spermatozoa. The removal of these proteins occurred with only minimal damage to the spermatozoa, as judged by sperm motility, ATP content and ability to exclude eosin. Spermatozoa treated with hypertonic solutions were unable to reach the freshly ovulated egg in the infundibulum and could not be found within the uterovaginal sperm storage tubules after uterovaginal insemination. However, if inseminated directly into the uterovaginal junction, spermatozoa were able to enter the sperm storage tubules, suggesting that the treatment limited their ability to migrate through the vagina. Loss of sperm fertilizing ability following simple centrifugation and washing treatments appears to result from removal of surface-associated proteins.

Cryopreservation of rooster sperm using methyl cellulose

Experiments were designed to determine when, during the cryopreservation process, sperm lose fertilizing capacity and whether the cryoprotectant, methyl cellulose (MC), could be used in combination with glycerol to cryopreserve sperm and remain in the inseminate without reducing fertility. Semen diluted in Minnesota Avian extender (MNA) and inseminated immediately had greater fertility (75%) than semen processed for cryopreservation (12 to 60%). The largest decreases in fertility were due to addition of glycerol to sperm and to cryopreservation. In another experiment, fertility of inseminates containing 0, 1, and 2% glycerol were 82, 29, and 21%, respectively, for eggs collected 2 to 5 d after insemination. When 0.5% MC was added to the same three treatments, fertility rates were 88, 63, and 69%, respectively. Semen cryopreserved in MNA containing 9% glycerol; MC + 3% glycerol; MC + 4% glycerol; MC + 9% glycerol; or 9% glycerol with the cryoprotectant removed post-thaw by dilution and subsequent centrifugation exhibited 59, 30, 35, 60, and 69% viable cells, respectively; and 65, 38, 46, 69, and 65% motile sperm, respectively. Sperm cryopreserved with MC and either 4 or 9% glycerol exhibited similar numbers of sperm binding to chicken perivitelline layers in vitro as did fresh sperm, whereas sperm frozen with MC and 3% glycerol bound oocytes with only 31% efficiency (P < 0.05). The extent to which cryopreserved sperm penetrated the perivitelline layer in vitro was independent of glycerol concentration, but was four times more efficient than that of fresh sperm (P < 0.05). The fertility rates of fresh semen, semen frozen in 9% glycerol with the cryoprotectant removed after thawing, and semen frozen in MC with either 3 or 4% glycerol were 87.4, 27.6, 0.8, and 0.5%, respectively (P < 0.05). The MC reduces the contraceptive effects of glycerol when inseminated with fresh sperm, but does not maintain fertilizing capacity in frozen-thawed sperm when used in combination with 3 or 4% glycerol.

Cryopreservation of poultry semen

1. The effect on fertility of storing the semen of fowl, turkey, gander or drake at -196 degrees C in a diluent with dimethylacetamide was investigated. 2. After artificially inseminating ducks, geese, turkeys and hens with freeze-thawed semen, the percentage of fertility was 69-90%, 81-90%, 80-90% and 75-85%, respectively.

Research note: the in vitro responses of vaginal tissue and chicken spermatozoa to glycerol

The fertilizing ability of glycerolized spermatozoa is apparently lost due to reactions between glycerol, spermatozoa, and vaginal tissue. Two experiments were conducted to determine the feasibility of using in vitro cultures to quantitatively assess these reactions. In the first experiment, vaginal slices alone, unglycerolized semen, and vaginal slices plus semen, all in a phosphate-buffered saline were studied. The media were separated into 14 fractions using HPLC and the absorbance of each fraction was measured at 0 and 1 h of incubation. In a second experiment the changes in absorbance of these fractions were examined for unglycerolized and glycerolized semen in vaginal cultures. When unglycerolized semen was added to the vaginal cultures, Fraction 55 appeared in significantly greater absorbance than in vaginal tissue or semen alone. The opposite occurred for Fraction 57, which decreased in absorbance after 1 h of incubation in semen-vaginal culture. Fraction 57 was increased in absorbance in the presence of glycerol in the semen-vaginal culture. Glycerol appears to block the appearance of Fraction 55 in the normal semen-vaginal reaction. This reaction may be responsible for the deleterious effects of glycerol on spermatozoal survival in vivo.

Contraceptive action of glycerol on chicken spermatozoa in oviducal organ-slice cultures

Chicken spermatozoa in diluent with and without glycerol were evaluated after coculture with oviducal tissues. The motility of glycerolized (G) spermatozoa was lower in the cultures of vaginal tissue than in uterine tissue. The percentage of dead, G spermatozoa increased in cultures of the vagina and uterus but not in infundibulum cultures. Glycerol significantly increased the percentage of dead spermatozoa in both vaginal and uterovaginal cultures when compared to nonglycerolized spermatozoa in the same cultures. The percentage of dead G spermatozoa was higher for semen in vaginal culture than in uterovaginal culture. Uterovaginal tissue appeared to protect spermatozoa from some of the detrimental effects of glycerol. Incubation time had a significant detrimental effect on motility and percentages of dead and abnormal spermatozoa regardless of semen or tissue treatment.

Cryopreservation of semen from unique lines of chicken germ plasm

Frozen semen is a practical means of preserving valuable germ plasm. Monitored samples of semen cryopreserved with glycerol for heterozygous, dominant marker stocks and for nine chromosomal rearrangement lines had sufficiently high fertility for germ-line retrieval. The results also indicated a potential for the genetic selection of certain lines for the freezability of spermatozoa, since stock and line differences in fertility occurred when previously frozen semen was used for insemination. Freezing the semen of stocks routinely reproduced provides insurance against possible disasters.

Physiological changes in fowl and turkey spermatozoa during in vitro storage

1. Although early work on semen storage has been rather empirical in approach, only basic research can provide a framework of biological mechanisms from which improvements in the techniques of cryopreservation and liquid semen storage can progress logically. 2. A major drawback in this work has been the lack of adequate tests for quantitating and differentiating aspects of 'fertility'. 3. Basic research has now provided techniques for assessing: sperm fertilising ability in terms of numbers of fertile eggs; the efficiency of hens' oviducts at accepting and retaining spermatozoa, and sperm 'quality' as motility, metabolism and plasma membrane patency. 4. These techniques may be used for a more critical assessment of the effects of both cryopreservation and liquid semen storage on sperm function, although the integrity of sperm surface proteins may be a more sensitive variable which has yet to be measured. 5. Further improvements in sperm cryopreservation technology are best approached through an understanding of the fundamental cellular and molecular changes which take place during freezing; thus far little is known of such changes in avian spermatozoa. 6. The ideal milieu for maintaining spermatozoa in liquid semen storage should mimic the environment of the oviducal sperm storage tubules; elucidation of the factors involved in progressing steadily.

Effects of glycerol on chicken spermatozoa incubated in vitro at 41 C in oviducal and embryonic cell cultures

Two experiments were conducted to determine the effects of glycerol on the quality and survival of spermatozoa in an in vitro system at 41 C in the presence of oviducal and other tissue cultures. The motility and percentages of abnormal and dead spermatozoa of glycerolized semen were significantly affected in a positive way by the presence of living cells. The most negative effect of glycerol on semen quality was observed with semen incubated in the tissue culture medium alone. Aspartate aminotransferase activity in the culture fluid revealed a harmful effect of glycerol on spermatozoa and culture cells.

Effect on fertility of low numbers of fowl spermatozoa inseminated in aqueous diluent or semen components of the fowl and turkey

A study was undertaken to compare the effect on fertility in the fowl of aqueous medium, natural homologous seminal plasma, heterologous turkey seminal plasma and whole turkey semen when whole fowl semen was excessively diluted with these media and inseminated fresh. High dilution with fowl seminal plasma resulted in the best fertility. Dilution with the turkey semen components produced fertility no different from that with aqueous diluent when the dose of spermatozoa was 5 X 5 or 10 X 10(6). The results of this study confirm that 5 X 5 to 10 X 10(6) good quality spermatozoa are sufficient to produce acceptable fertility in weekly inseminations of fresh semen. This enables good quality semen to be highly diluted. However, at high dilution rates there is a need to reconsider the composition of semen diluents, with respect to simulating as yet unknown properties provided by factor(s) in homologous ductus deferens seminal plasma.