Inseminating fresh or cryopreserved semen for maximum efficiency: implications for gene banks and industry

Poultry genetic heritage cryopreservation and reconstruction: advancement and future challenges

Poultry genetics resources, including commercial selected lines, indigenous breeds, and experimental lines, are now being irreversibly lost at an alarming rate due to multiple reasons, which further threats the future livelihood and academic purpose. Collections of germplasm may reduce the risk of catastrophic loss of genetic diversity by guaranteeing that a pool of genetic variability is available to ensure the reintroduction and replenishment of the genetic stocks. The setting up of biobanks for poultry is challenging because the high sensitiveness of spermatozoa to freezing–thawing process, inability to cryopreserve the egg or embryo, coupled with the females being heterogametic sex. The progress in cryobiology and biotechnologies have made possible the extension of the range of germplasm for poultry species available in cryobanks, including semen, primordial germ cells, somatic cells and gonads. In this review, we introduce the state-of-the-art technologies for avian genetic resource conservation and breed reconstruction, and discuss the potential challenges for future study and further extending of these technologies to ongoing and future conservation efforts.

Effect of glycerol concentration, glycerol removal method, and straw type on the quality and fertility of frozen chicken semen

The long-term semen cryopreservation is increasingly crucial for conservation of endangered livestock and poultry species. Glycerol is the most widely used cryoprotectant for freezing chicken semen. Continuous improvement in details with glycerol may help increase the fertility of post-thawed semen. Two experiments were performed in the present study to investigate the effects of glycerol concentration, removal method, and straw type on the quality of post-thawed sperm. In experiment 1, glycerol concentration (3%, 5%, 7%, 9%, 11%, and 13%) and glycerol removal method (final dilution ratio 1:1, 1:2, 1:4, 1:8, 1:16, and 1:20) combination groups were investigated for post-thawed sperm quality, residual glycerol concentration, and fertility to find the best combinations. Experiment 2 was performed to evaluate the effects of straw type (0.25 and 0.5 mL) and glycerol concentration (3%, 5%, 7%, 9%, 11%, and 13%) on the post-thawed sperm quality. Results showed that post-thawed sperm motility of 6 glycerol concentration groups were different (P < 0.01). Sperm motility of 5%, 7%, 9%, 11% and 13% was higher than that of 3% (P < 0.01). There was no difference among different concentrations of glycerol in VSL, VCL, VAP, ALH, WOB, BCF, LIN, or STR (P > 0.05). As for the glycerol removal method, sperm motility of 1:8 dilution was the highest, followed by 1:1 and 1:2, while the difference among groups was not statistically significant (P = 0.11). Glycerol concentration and removal method had no interaction effect on sperm motion parameters (P > 0.05). The highest fertility (48.70%) was found for the 5% and 1:2 combination. There was no difference for sperm motility between 0.25 and 0.5 mL straws (P > 0.05). Glycerol concentration and straw type had no interaction effect on the sperm motion parameters (P > 0.05). It can be concluded from these observations that the combination of 5% glycerol and 1:2 dilution rendered higher fertility should be suggested in practice, and that both 0.25 and 0.50 mL straws fit the present procedure.

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.

Preservation of Domesticated Honey Bee (Hymenoptera: Apidae) Drone Semen

Preservation of honey bee (Apis mellifera L., Hymenoptera: Apidae) sperm, coupled with instrumental insemination, is an effective strategy to protect the species and their genetic diversity. Our overall objective is to develop a method of drone semen preservation; therefore, two experiments were conducted. Hypothesis 1 was that cryopreservation (-196 °C) of drone semen is more effective for long-term storage than at 16 °C. Our results show that after 1 yr of storage, frozen sperm viability was higher than at 16 °C, showing that cryopreservation is necessary to conserve semen. However, the cryoprotectant used for drone sperm freezing, dimethyl sulfoxide (DMSO), can harm the queen and reduce fertility after instrumental insemination. Hypothesis 2 was that centrifugation of cryopreserved semen to reduce DMSO prior to insemination optimize sperm quality. Our results indicate that centrifuging cryopreserved sperm to remove cryoprotectant does not affect queen survival, spermathecal sperm count, or sperm viability. Although these data do not indicate that centrifugation of frozen-thawed sperm improves queen health and fertility after instrumental insemination, we demonstrate that cryopreservation is achievable, and it is better for long-term sperm storage than above-freezing temperatures for duration of close to a year.

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.