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A new nutrient-rich liquid capable of extending the life of fresh horse semen has been developed by Australian researchers.
The extender, added to horse semen after ejaculation, is able to support sperm function for a minimum of five days at room temperature, opening up new possibilities in the breeding industry.
By comparison, chilled semen will typically remain viable for around three days.
Cryopreservation of sperm has been employed for years, but it carries the risk of damage to cells arising from the freezing process. Thawed sperm also has a shortened lifespan, which can reduce the likelihood of conception.
The extender overcomes problems associated with the short lifespan of sperm, raising the possibility that fresh semen could be shipped further for breeding programs.
University of Newcastle postdoctoral researcher Dr Aleona Swegen told Horsetalk that the semen extender had been in development for some years.
Swegen said many of the harmful effects of chilling were due to membrane damage which occurred below about 15 degrees Celsius.
“Our idea was to avoid chilling altogether.
“However, if we weren’t going to restrict metabolism – and therefore the production of toxic by-products and depletion of energy which leads to cell death – by reducing the temperature, we needed to support it by ‘feeding’ the cells and including a range of antioxidants to scavenge the toxic metabolites.”
At the same time, the research team wanted to achieve this without including any biologically-sourced substances so that the medium itself wouldn’t be considered a biosecurity threat if crossing geographical borders.
“This,” she said, “is a particular concern for Australia as we do not have many of the diseases which are endemic in Europe, the United States, and Asia.”
Swegen said the extender fully supported sperm function for a minimum of five days at around 22 degrees C, though the researchers had many samples which still had commercially viable motility after two weeks.
“We are currently further refining the protocol for the processing of sperm prior to storage in our extender, the type of packaging to use, and strategies for eliminating the growth of microbes during storage.”
The first fertility trials will be undertaken in the 2017/2018 breeding season using mares sourced through Harness Racing Australia.
“We are confident that the extender will be ready for commercialisation by the following year,” Swegen said.
The project was instigated by Harness Racing Australia which was interested in improving per-cycle conception rates following insemination with chilled semen.
Swegen said she was grateful for the support of her supervisor, Laureate Professor John Aitken, and the work of her colleagues Dr Zamira Gibb and Ms Sarah Lambourne, and Dr Jen Clulow of Scone Equine Hospital, on the project.