Abstract
Background:
The Pesisir cattle are an indigenous genetic resource of Indonesia widely distributed in the coastal areas of West Sumatra. The breeding program still faces a major limitation, namely the restricted availability of superior sires, which may lead to a decline in the genetic quality of the population. The selection of Pesisir bulls is necessary to produce high quality frozen semen and constitutes a crucial component in sustainable genetic improvement efforts.

Aim:
This study evaluated semen quality in two groups of Pesisir bulls and identified candidate protein markers related to reproductive function based on molecular weight profiles.

Methods:
Five bulls were used and divided into a production group and a traditionally managed breeding group. Semen quality was assessed using Computer Assisted Sperm Analysis (CASA), while sperm protein profiling was performed using Gel Electrophoresis 1D SDS PAGE.

Results:
The results showed that semen quality in both management systems was within the normal range and met cryopreservation standards, with no significant differences (p > 0.05) in sperm motility and viability between groups. Protein analysis did not reveal group specific proteins and, 18 candidate proteins potentially involved in reproductive processes were identified, including those associated with sperm maturation, capacitation, acrosome reaction, and motility.

Conclusion:
These findings indicate that these proteins may serve as potential molecular markers of semen quality in Pesisir bull and suggest that bulls under traditional management possess comparable reproductive potential and may be considered as candidates for breeding programs aimed at genetic improvement.

Key words: Biomarkers; Pesisir bulls; Semen Quality; Sperm Protein; Reproductive.