Sperm protein profiles and their correlation with DNA integrity and protamine deficiency in Donggala bulls (Bos indicus): Implications for fertility assessment.

Background and aim: The reproductive efficiency of livestock, especially indigenous breeds such as Donggala bulls, is pivotal to successful breeding programs. While conventional semen parameters are widely used, molecular markers, such as sperm protein profiles and DNA integrity, are emerging as reliable indicators of fertility. This study aimed to characterize the sperm protein profiles of Donggala bulls and examine their correlation with sperm DNA integrity and protamine deficiency.

Materials and methods: Frozen semen samples were collected from six Donggala bulls (aged 5-7 years). Pre-freezing evaluations included progressive motility (via computer-assisted sperm analysis), sperm morphology (using Diff-Quik staining), DNA integrity (assessed by the acridine orange assay), and protamine deficiency (assessed by the chromomycin A3 assay). Protein concentrations were determined using the bicinchoninic acid assay, and protein profiling was performed using 1D sodium dodecyl sulfate polyacrylamide gel electrophoresis. Band intensities and distributions were analyzed using ImageJ. Statistical correlations were analyzed using a one-way analysis of variance and Pearson's correlation coefficients.

Results: Significant individual variation was observed in semen quality among bulls. Progressive motility ranged from 38.3% to 46.1%, DNA integrity from 79.5% to 96.8%, and protamine deficiency from 96.0% to 98.7%. The number of protein bands per sample varied between 8 and 11, with molecular weights ranging from 5 to 175 kilodaltons (kDa). Protein concentration ranged from 8.32 to 20.70 μg/mL. A 35 kDa protein band was notably absent in one bull, which may be linked to lower motility. Strong correlations were observed between sperm motility and DNA fragmentation (r = 0.628), protamine deficiency (r = 0.539), protein concentration (r = 0.658), and protein band expression (r = 0.788).

Conclusion: Sperm protein profiles in Donggala bulls are significantly correlated with DNA integrity and protamine deficiency, indicating their potential as molecular biomarkers for fertility prediction. These findings provide a foundation for integrating protein profiling into breeding soundness evaluations, suggesting that targeted proteomic analysis may enhance reproductive management strategies.