Abstract
Background:
Semen quality is a crucial determinant of male fertility, and seminal plasma proteins play an essential role in the regulation of sperm function, protection, and fertilization ability. Profiling these proteins can provide insights into fertility-associated markers in livestock, particularly in indigenous cattle such as the Aceh bull.

Aim:
This study aimed to determine the seminal plasma protein profile of Aceh bulls and analyze its relationship with semen quality parameters.

Methods:
Semen was collected once a week using an artificial vagina. The collected samples were evaluated both macroscopically and microscopically. Macroscopic evaluation included volume, color, pH, and consistency, while microscopic evaluation assessed mass movement, motility, viability, morphology, membrane integrity (MI), and acrosome integrity using an Olympus BX51 microscope. Sperm concentration was measured using an (SDM 6, Minitube, Tiefenbach, Germany). Seminal plasma proteins were analyzed using one-dimensional sodium dodecyl sulfate-polyacrylamide gel electrophoresis (1D SDS-PAGE).

Results:
Aceh bull semen had an average volume of 6.25 ± 1.25 ml, a pH of 6.7 ± 0.04, a milky white color, and medium viscosity. Microscopic evaluations revealed motility of 76.30% ± 3.79%, concentration of 1541 ± 79.9 × 106/ml, viability of 76.44% ± 3.21%, MI of 79.77% ± 4.59%, morphology of 88.04% ± 4.65%, and intact acrosome integrity of 93.58% ± 0.2%. The protein concentration ranged from 151.38 to 158.34 μg/ml. The seminal plasma protein concentration ranged from 151.38 to 158.34 μg/ml. 1D SDS-PAGE revealed distinct banding patterns based on the molecular weight (MW). Bulls with sperm motility >75% exhibited nine protein bands, whereas those with motility <75% displayed ten bands. Higher MW bands were absent in some individuals, particularly within the range of 270–176 kDa. The protein MW distribution was negatively correlated with sperm motility (r = −0.48), concentration (r = −0.18), viability (r = −0.47), MI (r = −0.46), morphology (r = −0.46), and acrosome integrity (r = −0.47). No significant differences in sperm concentration, viability, morphology, or acrosome integrity were observed between bulls, whereas MI differed among individuals.

Conclusion:
The seminal plasma protein profiles of Aceh bulls showed a negative correlation with semen quality parameters. Lower MW proteins were associated with higher semen quality, indicating their potential as fertility assessment biomarkers in Aceh bulls.

Key words: Aceh bulls; Fertility; Protein profile; Semen quality; Seminal plasma.