Abstract
Background:
The Kokok Balenggek rooster (KBR), with its distinct phenotypes—Biriang, Balang, Kinantan, and Kuriak—offers a unique opportunity to study variations in semen characteristics and protein profiles. Understanding these variations can aid in the development of better management strategies for poultry breeding programs.

Aim:
This study aimed to characterize the spermatozoa and seminal plasma protein profiles based on molecular weight (MW) across four phenotypes of KBRs, focusing on semen parameters, such as motility, viability, and protein concentration.

Methods:
Semen samples were collected from the KBR of four phenotypes: Biriang, Balang, Kinantan, and Kuriak. The parameters analyzed included semen volume, color, smell, consistency, sperm concentration, motility, viability, abnormality, plasma membrane integrity, and protein concentration. Protein profiles of spermatozoa and seminal plasma were analyzed using MW markers via gel electrophoresis.

Results:
The results revealed significant variations in semen volume (p < 0.05) and protein concentration (p < 0.01), with the Kinantan phenotype exhibiting the highest protein concentration (2.23 mg/ml). Sperm motility (p < 0.05) and viability (p > 0.05) were highest in the Biriang, Balang, and Kinantan phenotypes, whereas the Kuriak phenotype showed lower motility (64%, p < 0.01). Protein profile analysis indicated the presence of proteins in sperm with MWs of 10, 25–35, 35–45, 45–65, and 100 kDa and in seminal plasma with MWs of 10, 20–25, 25–35, 45, 65, 75, 140, and
180–245 kDa, respectively, across all phenotypes.

Conclusion:
This study highlighted variations in sperm characteristics and protein profiles among KBR phenotypes, with the Kuriak phenotype showing lower motility, providing insights for improving genetic resource management and semen preservation.

Key words: Keywords: Kokok Balenggek roosters, Protein, Seminal plasm, Sperm