Chitosan Nanoparticle Delivery Enhances the Antibacterial Performance and Bioactivity of Bovine Lactoferricin against <i>Staphylococcus aureus</i> -Associated Mastitis

Bioactive peptides such as bovine lactoferricin (BLfcin) are gaining attention as functional agents to enhance animal health and reduce antibiotic reliance in dairy production. This study developed a chitosan nanoparticle (NP) delivery system to enhance the stability and efficacy of BLfcin, an antimicrobial peptide. BLfcin-loaded NPs (101.2-135.9 nm; +19.83 to +21.37 mV) showed high encapsulation efficiency (72.18%) and significantly improved antibacterial activity against <i>S. aureus</i> and <i><i>E. coli</i></i> compared to free BLfcin. Transcriptomic analysis revealed that BLfcin NPs suppressed genes related to ribosomes, ABC transporters, and two-component systems. In a murine mastitis model, BLfcin NPs reduced the bacterial burden, alleviated mammary inflammation, and enhanced antioxidant enzyme levels without inducing toxicity. These results demonstrate that chitosan NPs effectively potentiate the antimicrobial and immunomodulatory effects of BLfcin, offering a promising nanotherapeutic strategy for nonantibiotic mastitis management.