New technology for long-term liquid storage of chicken semen by arresting energy metabolism

Tsukuba, Japan—In vitro sperm preservation is vital for bird species with large eggs that are unsuitable for cryopreservation. Refrigerated storage is a key method that is favored for its simplicity, affordability, and industrial feasibility. However, bird sperm, especially chicken sperm, are susceptible to damage from low temperatures. In chickens, refrigerated storage notably impairs sperm cell membranes and mitochondria, drastically reducing fertilization capacity within 6 24 h. Despite this deterioration in fertilization ability within such a short period, chicken sperm exhibits remarkable durability, retaining viability and fertilization ability for up to three weeks after entering the female reproductive tract.

Researchers explored the regulatory mechanisms sustaining and disrupting the fertilization capacity of chicken sperm. They discovered that refrigerated storage-induced fertility impairment originates from an influx of calcium ions into sperm cells. Experimentation with specific chelators to extract calcium ions from within and around the cells revealed a reversible deactivation of sperm fertilization functions. This was validated by in vivo fertility tests, demonstrating that sperm could be refrigerated for more than three days, exceeding previous storage durations.

The team delved deeper into this phenomenon, focusing on energy metabolism. They observed that removing intra- and extra-cellular calcium impacts the energy metabolism dynamics associated with chicken sperm, inducing a physiological dormancy-like state. This state features characteristics like cell hypoxia, lowered pH, and intermittent motility.

These results suggest that calcium acts as a molecular switch, regulating the dormancy and reactivation of fertilization functions in chicken sperm. This switch may be involved in the reproductive strategy of poultry sperm, which can survive several weeks in the female reproductive tract, synchronizing with ovulation to fertilize eggs. This innovative, straightforward technique for long-term cold storage of sperm could significantly benefit the poultry breeding industry, offering cost-effective and efficient propagation methods for rare genetic resources.

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This work was supported by Japan Society of the Promotion of Science (JSPS) KAKENHI 17KK0150 and 21H02377 (to Atsushi Asano). Pangda Sopha Sushadi is a recipient of Indonesia Endowment Fund for Education Scholarship S-1188/LPDP.4/2020.

_{Original Paper}

Title of original paper:
Arresting calcium-regulated sperm metabolic dynamics enables prolonged fertility in poultry liquid semen storage

Journal:
Scientific Reports

DOI:
10.1038/s41598-023-48550-2

_{Correspondence}

Assistant Professor ASANO, Atsushi
Institute of Life and Environmental Sciences / Tsukuba-Plant Innovation Research Center, University of Tsukuba

Dr. Vimal Selvaraj (Professor of Integrative Physiology)
Department of Animal Science, College of Agriculture and Life Sciences, Cornell University, USA

_{Related Link}

Institute of Life and Environmental Sciences
Tsukuba-Plant Innovation Research Center