Sperm metabolomics identifies freezability markers in Duroc, Landrace, and Large White boars

Cryopreservation of boar semen is widely applied in the conservation of genetic resources and animal breeding to enhance the utilization efficiency of superior boars. However, accurately identifying individuals with good freezing tolerance in boar sperm remains challenging. In this study, based on the differences in sperm motility before and after cryopreservation from 328 boars, we selected six boars each from the Duroc, Landrace, and Large White breeds, and categorized them into poor freezability ejaculates (PFE) and good freezability ejaculates (GFE) groups for sperm metabolomic analysis. A total of 1288 metabolites were identified using both positive and negative ion modes. There were 148 differentially expressed metabolites between the GFE and PFE groups, which were enriched in pathways such as alanine, aspartate and glutamate metabolism; arginine biosynthesis; D-amino acid metabolism; histidine metabolism; beta-alanine metabolism; citrate cycle (TCA cycle); pantothenate and CoA biosynthesis; and pyruvate metabolism. Further analysis, including ROC curve evaluation, identified seven potential biomarkers for sperm cryopreservation. Argininosuccinic acid, asparagine, L-aspartate, fumarate, D-ornithine, DL-serine and histidine were tightly interconnected in a series of amino acids metabolism. In conclusion, our findings imply that differences in certain amino acid biosynthetic pathways contribute to the variations in freezing tolerance of boar sperm.