In vitro comparison of fowl sperm viability in ejaculates frozen by three different techniques and relationship with subsequent fertility in vivo

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.

Comparative costs of programmes to conserve chicken genetic variation based on maintaining living populations or storing cryopreserved material

1. There have been substantial losses of chicken lines kept for research in recent years and the objective of this research was to critically review alternative methods of preserving genetic resources. 2. The costs of programmes using living populations, semen cryopreservation and reconstitution, and ovary and semen cryopreservation and reconstitution were evaluated over 20 years using biological parameters of cryopreservation and population reconstitution that were derived from the literature. 3. Keeping live populations was most cost effective for periods of up to three years, but keeping live populations is increasingly difficult to justify with longer periods and any research population that will not be used within five years should be cryoconserved and in situ maintenance discontinued. 4. The rapid reconstitution possible using ovaries and semen would allow the inclusion of cryopreserved material in a short-term research project with the cost of recovery included in the budget. The low cost of cryoconservation suggests that all avian material should be conserved and reconstituted when needed for research.

Comparative cryopreservation of avian spermatozoa: effects of freezing and thawing rates on turkey and sandhill crane sperm cryosurvival

A comparative approach was used to evaluate semen cooling rates, thawing rates and freezing volume on the cryosurvival of avian sperm. Turkey (Meleagris gallopavo) and sandhill crane (Grus canadensis) sperm were cryopreserved with dimethylacetamide (DMA) concentrations ranging from 6% to 26%. Experiments evaluated the efficacy of (1) rapid, moderate and slow cooling rates, (2) rapid and slow thawing rates, and (3) final volume of semen frozen (0.2 mL compared to 0.5 mL). For crane sperm only, additional experiments were conducted to evaluate the effect of sucrose on cryosurvival. The functionality of frozen/thawed crane sperm was evaluated by fertility trials. For all studies, sperm viability was assessed using the nigrosin-eosin stain. Higher percentages of crane and turkey sperm maintained intact membranes when frozen with moderate or slow cooling rates compared to rapid cooling rates (P<0.05), regardless of DMA concentration. Turkey sperm viability was not affected by thawing rate at any DMA concentration (P>0.05). Crane sperm viability was only affected by thawing rate for the 24% DMA treatment, where moderate thawing was better than slow thawing (P<0.05). Sperm viability was not affected by the semen volume used for freezing for either species (P>0.05). The percentage of membrane-intact crane sperm at lower DMA concentrations was improved by addition of 0.1M sucrose (P<0.05) but not 0.29 M NaCl. The mean fertility rate from frozen/thawed crane semen was 57.5%, and 71.4% of the fertile eggs hatched. The viability of crane sperm was always greater than turkey sperm, regardless of cooling rate, thawing rate or volume of semen frozen. These data verify avian-specific differences in sperm cryosurvival, further emphasize the need for species specific studies to optimize cryopreservation protocols.

Capillary electrophoresis with laser-induced fluorescence detection for ATP quantification in spermatozoa and oocytes

We describe a new capillary electrophoresis laser-induced fluorescence (CE-LIF) method for the quantification of adenosine 5'-triphosphate (ATP) in spermatozoa and oocytes. The optimization of the precapillary derivatization reaction between ATP and 4,4-difluoro-5,7-dimethyl-4-bora-3a,4adiaza-s-indacene-3-propionyl ethylene diamine hydrochloride (BODIPY FL EDA) has been described. BODIPY-ATP conjugate was analysed in an uncoated fused silica capillary of 75 μm ID and 50 cm effective length using a 10 mmol/L tribasic sodium phosphate buffer, pH 11.5, at 22 kV in <5 min. A good reproducibility of intra- and inter-assay tests was obtained (CV = 4.55% and 7.14%, respectively). With respect to our previous CE-UV assay, the new method showed an improvement in sensitivity that was about 120-fold (limit of quantification, 0.15 vs 18 μmol/L). Method applicability was proven on the reproductive cells of several animal species (roosters, horses, sheep and goats). Due to the elevated sensitivity, the new assay allows the measurement of adenosine 5'-triphosphate levels from just 20 oocytes. Considering that ATP concentration in reproductive cells is related to the mitochondrial integrity after cryopreservation, the proposed method could be a useful tool in assisted reproductive technologies.

Differences in semen freezability and intracellular ATP content between the rooster (Gallus gallus domesticus) and the Barbary partridge (Alectoris barbara)

This study aimed to compare viability, ATP content, and DNA integrity of rooster (Gallus gallus domesticus) and Barbary partridge (Alectoris barbara) fresh and frozen spermatozoa in order to identify factors possibly related to differences in semen freezability. Ejaculates were obtained from March to May by the abdominal massage method from 3 adult roosters and 12 adult Barbary partridges. Semen was frozen with different cryoprotectants using Lake's diluents as a base medium: 1) glycerol 11%; 2) glycerol 11% and trehalose 70 mmol/L; 3) dimethylacetamide (DMA) 6%; 4) DMA 6% and trehalose 70 mmol/L. Both fresh and frozen semen showed a lower viability and higher intracellular ATP concentrations in the Barbary partridge compared with the rooster (P < 0.05). In the Barbary partridge, semen viability after thawing did not differ among the 4 media used, but glycerol showed positive effects in avoiding a significant loss of ATP after thawing, compared with DMA containing media (P < 0.05). On the other hand, in the rooster a higher viability was recorded when semen was frozen in glycerol containing media compared to DMA (P < 0.0001), while ATP values significantly decreased after thawing (P < 0.05) without showing any differences among the semen frozen in the 4 different media. DNA integrity, as evaluated by the comet assay, was assessed only in frozen semen. In the Barbary partridge, mean scored parameter did not differ significantly among semen frozen in the 4 different media. In the rooster DNA fragmentation was higher in DMA ctr medium compared with the other media and with values found in Barbary partridge semen frozen in the same medium (P < 0.001). In both species, the addition of trehalose did not show any positive effects on viability, ATP levels and DNA integrity after thawing. In conclusion, species-related differences in semen features exist between the rooster and the Barbary partridge and the wide variation observed in ATP levels may account for differences in semen freezability between the two species.

Dimethylacetamide can be used as an alternative to glycerol for the successful cryopreservation of koala (Phascolarctos cinereus) spermatozoa

Swelling of koala sperm chromatin following cryopreservation has largely been attributed to the absence of intermolecular disulfide cross-linkages in the marsupial sperm nucleus. Fish spermatozoa also lack disulfide bonds within their chromatin, but have been successfully cryopreserved. The present study examined the hypothesis that the cryoprotectants used for fish sperm cryopreservation would confer a similar degree of protection on koala spermatozoa. Three concentrations each of five cryoprotectants (dimethyl sulfoxide, methanol, propylene glycol, ethylene glycol and dimethylacetamide (DMA)) were evaluated. Each treatment was compared against an established koala sperm cryopreservation protocol that uses 14% glycerol. Post-thaw assessment of progressive motility, plasma membrane integrity and mitochondrial membrane potential (MMP) revealed that protocols using 15% DMA achieved 62.2 ± 3.6% (P < 0.05) sperm survival, of which 79% (P < 0.05) had high MMP, an improvement of 32% and 40%, respectively, over sperm frozen in 14% glycerol. The percentage of spermatozoa with swollen nuclei was also lowest when frozen in 15% DMA, both immediately after thawing (18.0 ± 3.5%; P < 0.05) and after 2 h incubation at 35°C (35.8 ± 4.4%; P < 0.05). A second study was conducted to determine the optimal concentration of DMA for use in the cryopreservation of koala spermatozoa. High DMA concentrations (17.5% and 20%) resulted in significantly lower proportions of live spermatozoa showing high MMP immediately after thawing compared with spermatozoa frozen in the lower concentrations. The percentage of koala spermatozoa with swollen chromatin following cryopreservation was not affected by DMA concentration.

Potential application of sperm bearing female-specific chromosome in chickens

This paper reviews studies on sex reversal experiments in chickens, production of sperm bearing a female-specific chromosome, its application for poultry resources and finally a mechanism of sex differentiation of gonads in the chicken.

Semen cryopreservation for ex situ management of genetic diversity in chicken: creation of the French avian cryobank

The need for semen preservation in domestic birds is a result of the reduction in genetic variability of domestic bird livestock and of the increasing risk of line extinction for health and safety reasons. Cryopreservation of embryos and primordial germ cells (PGC) is not routinely feasible in birds. The project therefore involved semen frozen in optimal safety and traceable conditions. Whole blood samples were also frozen to provide samples of analyses of genomes and health status. The feasibility of using ex situ conservation, i.e., collecting biological material to be stored outside the usual production area of the species (ex situ genetic stock), to preserve and manage rare breeds was tested with 4 subfertile populations: 3 rare experimental lines used for research into energy metabolism (R+), growth (Y33), and immunity (B4/B4), reared under known health status and the oldest endangered patrimonial French breed, the Gauloise dorée with an unknown health status. A general infrastructure was set up for the health screening and remediation of diseases, collection and storage of frozen cells and 2 sites were created for the storage of frozen samples. The screening and remediation of diseases of the Gauloise dorée, which was contaminated with various Salmonella and Mycoplasma strains, was achieved by successive treatment of parents, incubated eggs and young chicks with Baytril followed by Tiamulin. For each line, 474 to 994 semen straws have been frozen, thawed, and the semen evaluated. Insemination of frozen-thawed semen into females of the same genetic origin or of an egg-type commercial breed produced chicks in every case. For the most subfertile lines, insemination with egg-type females significantly increased the reproductive success. In conclusion, we report on the benefits of a semen and blood cryobanking complex for the management of endangered lines and strains of domestic birds. Current stocks made possible the restoration of more than 96% of the initial genome. This project also provided technical solutions to resolve some of the health problems frequently encountered for gene preservation in poultry.

A method for cryopreserving chicken primordial germ cells

This study established a method for preserving chicken primordial germ cells (PGC) that enables long-term storage in liquid N. Gonads were harvested from stage 27 chick embryos and pooled in groups of 5, 10 (10E), or 20 embryos, contributing gonads to the cell suspension. The gonadal cells, including PGC, were then frozen in 1 of the following cryoprotectant treatments: 2.5% dimethyl sulfoxide (DMSO), 5% DMSO, 10% DMSO, 2.5% ethylene glycol (EG), 5% EG, 10% EG, and 0% cryoprotectant as a control. The cells were liberated and frozen in a biosecure cryopreservation straw at a rate of -1 degrees C/min until reaching -85 degrees C and were then plunged into liquid N (-196 degrees C), in which they were stored until analysis. Flow cytometry was used to analyze the PGC post-thaw. The PGC marker stage-specific embryonic antigen-1, which was detected with goat antimouse IgM fluorescein isothiocyanate, was used to label all PGC, and propidium iodide was used to detect cells with compromised cell membranes. There was an interaction effect for the number of viable PGC per individual embryo (P < or = 0.05). The highest level (183.6 +/- 28.4) of viable PGC per individual embryo was observed for 10% EG with 10E and was significantly higher (P < or = 0.05) than cryopreservation in 2.5% DMSO with 10E and 20 embryos, 2.5% EG with 10E, 5% EG with 10E, and all 0% cryoprotectant treatments. No statistical interaction (P > 0.05) was observed for the percentage of viable PGC. However, the highest percentage (80.6%) was observed at 10% EG with 10E. It was demonstrated that PGC were successfully frozen, and the most effective treatment was 10% EG with 10 embryos/straw.

Animal Genetic Resources Conservation in the Netherlands and Europe: Poultry Perspective

Increased global use of highly productive breeds of farm animals has been coupled to loss of genetic diversity in most species. In European countries, various governmental, non-governmental, and private organizations try to preserve genetic diversity of livestock in situ (e.g., by stimulating the use of indigenous, rare breeds by farmers; in nature reserves; or in noncommercial farms). In the case of poultry, maintaining in situ populations of the noncommercial (fancy) breeds largely relies on hobby farmers. In addition to in situ conservation, gene banks are being established for ex situ conservation. In at least 2 countries, France and The Netherlands, there are limited collections of frozen semen of rare poultry breeds. Since 2003, the CGN has started with a more systematic effort to collect, freeze, and store semen of indigenous Dutch poultry breeds. At present, the CGN gene bank contains semen of 11 Dutch rare poultry breeds. Also, CGN has performed research on the methodology for cryopreservation of fowl semen. This recent work was focused on finding a suitable replacement for glycerol, which is contraceptive in the hen, as a cryoprotectant. For reasons of hygiene and sample identification, we favored straw freezing, as opposed to the highly effective pellet freezing method. A significant interaction was found between cooling rate and cryoprotectant concentration. Best post-thaw sperm quality was obtained when combining 0.6 mol of dimethylacetamide/L with a cooling rate of +/- 200 degrees C/min. Inseminations twice per week with 0.3 billion sperm per insemination resulted in 97 and 88% fertilized eggs with fresh and frozen semen, respectively. In 2005, CGN has used this straw freezing method to extend the collection of poultry semen in the Dutch gene bank.

Avian Genetic Resource Banking: Can Fish Embryos Yield Any Clues for Bird Embryos?

Cryopreservation of avian germplasm is becoming better understood and more commonly practiced. However, one area that would be of great benefit for genome resource banking is the preservation of avian embryos. Little is know about the cryobiology of avian embryos, and they have never been successfully cryopreserved. However, it is likely that they share many of the challenges of other yolk-filled multicompartmental embryos. For example, the fish embryo has 1) a large overall size, resulting in a low surface-to-volume ratio, which retards water and cryoprotectant efflux/influx; 2) large-sized cells, such as the yolk, which could increase the likelihood of membrane disruption by intracellular ice formation; 3) compartments, such as the blastoderm and yolk, with differing permeability properties; and 4) susceptibility to chilling injury. Both the avian and fish systems share many physical and anatomical properties, and it is predicted that some of the same permeability barriers would exist in both as well. Although the systems are similar, some of the goals, and thus the practices, to protect the genome may be quite different. One of these major goals in avian developmental biology is to produce chicken:chicken transgenic animals, especially those with germ line transmission. Producing efficient germ line transmissions and being able to cryopreserve these transmissions would be extremely beneficial to both basic and agricultural science. This could be accomplished through the cryopreservation of embryonic gonadal tissue followed by grafting into a host. The gonadal/tail-graft system would provide an advantage for cryopreservation because it is small (in comparison with the whole embryo), has fairly uniform tissue, and contains the essential primordial germ line cells capable of recreating the genetic line of interest. Moreover, because the chicken is such a robust model for most other avian species, the cryopreservation of the gonadal/tail-graft may potentially open up similar treatments for other commercially important species.

The National Animal Germplasm Program: Challenges and Opportunities for Poultry Genetic Resources

In the United States, poultry genetic resources have consolidated because of economic pressures. Such consolidations can potentially jeopardize the poultry industry and the ability of research communities to respond to future challenges. To address the loss of genetic resources for all livestock and aquatic species, USDA established the National Animal Germplasm Program (NAGP) in 1999. Since the initiation of NAGP, population surveys have been conducted on nonindustrial chicken and turkey breeds. These surveys not only provide insight into breed status, but also serve as a benchmark for future comparisons. The survey results revealed that 20 chicken breeds and 9 turkey breeds were in various stages of being lost. The NAGP has initiated an ex situ repository for cryopreserved germplasm and tissue that already contains 59 chicken lines and 2,915 tissue samples. As the NAGP, along with its industry and university partners, continues developing the ex situ collection, there are research opportunities in cryopreserved tissue utilization and studies of genetic diversity. For cryopreserved tissues, several key research areas include improving the cryopreservation protocols for rooster and tom semen by using cryoprotectants other than glycerol and utilizing embryonic cells. Although surveys have been conducted on public research lines and rare breeds, there is a void in understanding the level of genetic diversity present in U.S. poultry populations. Therefore, an opportunity exists to perform a series of genetic diversity studies using molecular- based approaches. Such an evaluation can help clarify population differences between research lines and rare breeds and, thereby, facilitate conservation strategies. There appears to be growing consumer interest in poultry products derived from heritage breeds and/or poultry raised in nonindustrial production systems. Although the depth of such market trends is unknown, such an interest may provide an important niche for rare poultry breeds and, thereby, strengthen the genetic base.

Effects of supplemental vitamin E during the mature period on the reproduction performance of Taiwan Native Chicken cockerels

One-day-old Taiwan native male chicks were fed with maize-soybean rearing diets without supplemental vitamin E to 23 weeks of age. From 23 to 52 weeks of age, the cockerels (n = 90) were assigned at random to 5 dietary treatments and fed with maize-soybean diets supplemented with 0, 20, 40, 80 and 160 mg/kg of vitamin E (dl-alpha-tocopherol acetate). Pullets (225) of the same age were fed with standard diets throughout. They were artificially inseminated with one dose of 0.04 ml/bird intact and 5-fold diluted pooled semen at 31 to 43 weeks of age and at 49 weeks of age, respectively. The criteria evaluated included: semen quality, fertility and maximum and effective duration of fertility, blood characteristics, body and testes weight. Supplemental vitamin E did not affect cockerels' effective duration of fertility and percentage of fertility. However, when pullets were inseminated with diluted semen, supplementing 160 mg/kg vitamin E increased the maximum duration of fertility at 49 weeks of age. Cockerels receiving 40 to 160mg/kg supplements had higher sperm viability and motility after 39 weeks of age and those fed 80 mg/kg had higher sperm concentration at 39 weeks of age. Cockerels receiving supplements of more than 40 mg/kg vitamin E had higher body weight gain. Plasma cholesterol and testosterone were not affected by supplemental vitamin E. However, plasma luteinising hormone (LH) concentration was lower in cockerels fed 160 mg/kg. Lack of supplemental vitamin E over 39 weeks was associated with lower semen quality but did not reduce the proportion of fertile eggs laid by inseminated hens, perhaps because the insemination dose compensated for low sperm quality. We found that the maximum duration of fertility might be improved by supplementing 160 mg/kg vitamin E at 49 weeks of age.

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.

Sperm function in workers exposed to N,N-dimethylformamide in the synthetic leather industry

OBJECTIVE

To determine whether occupational exposure to N,N-dimethylformamide (DMF) for men has adverse effects on sperm function.

DESIGN

Cross-sectional study.

SETTING

A synthetic leather factory in Taiwan.

PATIENT(S)

Twelve DMF-exposed workers in a synthetic leather factory and 8 socioeconomically matched control workers from another non-DMF-exposed manufacturing plant in the vicinity were recruited.

INTERVENTION(S)

None.

MAIN OUTCOME MEASURE(S)

Breathing-zone monitoring of DMF exposure covering the full work shift was implemented on each participant. Urine specimens were collected from each worker immediately after their work shift in parallel with environmental sampling. Environmental DMF and urinary N-methylformamide (NMF) levels were measured by gas chromatograph. Analysis of semen samples was performed to measure semen volume, sperm concentration, morphology, and motility in accordance with World Health Organization criteria.

RESULT(S)

Both conventional microscopy and computer-assisted semen analysis showed that sperm motility in DMF-exposed group was significantly reduced from that in controls. Motility parameters were related to urinary NMF in a dose-response manner but were not related to airborne DMF.

CONCLUSION(S)

Workers occupationally exposed to DMF could be at risk of sperm motility perturbation. The responsible toxicant for the alterations of sperm function could be the active NMF metabolite instead of DMF, but this conclusion warrants a further complete investigation.

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.