Abstract

Background:
Tropical heat and humidity induce oxidative and thermal stress that threaten male fertility, yet the seminal plasma mechanisms that sustain sperm function under these conditions remain poorly understood in goats.

Aim:
This study evaluated semen quality and characterized the seminal-plasma proteome of Saanen bucks raised under Indonesia’s tropical conditions to identify molecular adaptations associated with fertility resilience.

Methods:
Three healthy bucks (five ejaculates each) were examined for sperm motility, viability, abnormality, membrane and acrosome integrity, and kinematics using computer-assisted sperm analysis (CASA). Seminal-plasma proteins were separated by one-dimensional SDS–PAGE and annotated through Gene Ontology enrichment.

Results:
While most semen traits and kinematics were comparable among bucks, abnormality and acrosome integrity differed significantly (p < 0.05). A conserved extracellular, vesicle-associated proteome was identified—including BSP1, BSP3, BSP5, ANXA5, ALB, HSPA1A, HSP90AA1, CLU, GPX5, and SOD1—with minor inter-individual variation in LTF, FN1, SPP1, and A2M. Enrichment (FDR < 0.05) highlighted extracellular region, vesicle, and cytokine-regulatory pathways.

Conclusion:
This study provides the first proteomic evidence of seminal plasma adaptation to tropical heat stress in Saanen bucks, revealing a stable core of chaperone, antioxidant, and membrane-coating proteins that safeguard sperm function. These findings establish a novel proteomic basis for heat-resilient fertility and support the development of protein-based screening tools for sire selection and reproductive management in tropical dairy-goat systems.

Key words: Sperm; Oxidative stress defense; Molecular chaperones; Saanen fertility biomarkers; Reproductive adaptability.