In modern pig breeding, genetic progress can be achieved more quickly by using younger boars for semen production and artificial insemination.
The challenge is that the boars must reach sexual maturity to produce semen, and the sperm cells must have good quality to ensure high fertility in the field.
– It can be difficult to determine when a boar should start being used for semen production. Today, standard tests are used to measure sperm concentration, motility, and morphology. However, there is a need for more analysis methods to increase our knowledge, Shrestha explains to inn.no.
Asmita Shrestha's research aimed to map the molecular and functional changes in boar semen associated with sexual maturation.
– We followed young Duroc boars from the time they began producing semen and over time, analyzing the semen using advanced methods. Metabolomics was used to identify changes in metabolites, transcriptomics to understand molecular mechanisms, and functional tests to assess sperm quality.
The study identified key metabolites in semen, such as glutamate, alanine, aspartate, choline, and taurine, whose concentrations changed with age and could serve as potential biomarkers.
– We also found that more sexually mature boars showed significant improvements in sperm motility, viability, DNA integrity, and tolerance for storing semen doses over time, says Shrestha.
The work lays the foundation for developing new molecular biomarkers that can help determine the optimal time for young boars to start producing semen doses for breeding purposes.
– This could help make Norwegian pig production even more efficient and accelerate genetic progress, according to the PhD candidate at University of Inland Norway.
The title of Asmita Shrestha's dissertation is «Investigation of biomarkers for sexual maturation in boar semen using metabolomics, transcriptomics, and sperm quality analyses.»
Key findings of the PhD research:
- We identified key metabolites (glutamate, alanine, aspartate, choline) as potential biomarkers for sexual maturity. Their concentration levels help characterize reproductive development in young Duroc boars.
- We mapped the complete "metabolic fingerprint" of boar semen, identifying several key biological pathways (e.g., porphyrin metabolism, taurine and hypotaurine metabolism, glycerolipid metabolism) that change significantly during sexual maturation.
- We confirmed that functional sperm quality improves with age. Mature boars showed better sperm movement, improved DNA integrity, and increased tolerance for sperm storage, with most sperm quality parameters stabilizing after 8 months of age.
- We profiled the sperm transcriptomic landscape to identify complex regulatory networks that provide deeper insights into the biological processes underlying sexual maturation.