Seminal plasma metabolomic profiles are associated with semen quality and age-related differences in Duroc boars

Boar semen quality and age are vital for successful fertility management in the swine industry. Understanding how seminal plasma (SP) metabolites vary with semen quality and age is essential for optimizing breeding strategies. This study aimed to determine whether SP metabolite profiles and semen quality are associated with Duroc boar age. A total of 58 ejaculates were collected from 38 Duroc boars and categorized via semen quality into the following categories: GOOD (≥75 % motility and ≥75 % normal morphology, n = 29) and POOR (<75 % motility and <75 % normal morphology, n = 29). Ejaculates were also classified by boar age as follows: YOUNG (8-18 months, n = 15), ADULT (19-36 months, n = 24), and OLD (37-48 months, n = 19). On average, boar age was 26.2 ± 11.3 months. YOUNG boars (343.2 × 10⁶ sperm/mL) had a higher sperm concentration than ADULT boars (285.6 × 10⁶ sperm/mL, P = 0.016) but did not differ compared to OLD boars (297.3 × 10⁶ sperm/mL, P = 0.062). In ADULT boars, the sperm concentration was higher in GOOD compared to POOR quality (327.4 vs. 243.8 × 10⁶ sperm/mL, P = 0.002). Similarly, OLD boars with GOOD quality showed higher sperm concentration than POOR quality sample (348.6 vs. 245.9 × 10⁶ sperm/mL, P = 0.002), whereas no significant difference was observed in YOUNG boars (P = 0.782). Metabolomic analysis revealed differences in SP metabolite profiles related to semen quality and age. From a total of 50 identified metabolites, 17 showed significantly higher concentrations in GOOD quality sperm (P < 0.05). Age-related interactions revealed that OLD boars with GOOD semen quality had enriched levels of several metabolites, including aspartate, valine, and tryptophan, which are associated with hormonal regulation, energy metabolism, and antioxidant defense, suggesting potential biomarkers for sustained fertility. These findings indicate that SP metabolite profiling could serve as a biomarker-based tool to support semen quality assessments and optimize boar culling strategies, ultimately enhancing reproductive efficiency and extending boar longevity.