Immunoglobulin Y (IgY) Derived from Egg Yolk as a Non-Antibiotic Agent for Mitigating E. coli in Dairy Goat Mastitis: A One Health Perspective

Mastitis caused by Escherichia coli remains a significant health and productivity problem in the Indonesian dairy goat sector, and increasing concerns regarding antimicrobial resistance (AMR) have prompted the search for non-antibiotic alternatives to conventional treatments. This study conducted a preliminary evaluation of Immunoglobulin Y (IgY), a natural antibody derived from chicken egg yolks, as a potential supportive agent against E. coli-associated mastitis. Chickens were immunized with heat-inactivated E. coli ATCC 25922 to generate specific IgY, which was subsequently purified using the caprylic acid method. IgY concentration and purity were determined spectrophotometrically, providing a reliable measurement of the antibody yield. Antibacterial activity was assessed using two in vitro approaches: a Growth Inhibition Assay on solid media and a Total Plate Count (TPC) test in liquid culture. The highest IgY concentration obtained was 80.54 mg/mL on Day 40. At a 4 mL dose, IgY produced an inhibition zone of 9.67 mm, whereas the amoxicillin control produced 18.67 mm. Although the inhibition remained below standard interpretive thresholds, indicating limited activity in the diffusion-based assay, the TPC test revealed a partial reduction in bacterial load at the same dose, suggesting that higher IgY concentrations may be required to achieve consistent functional effects in broth cultures. Overall, these findings confirm that IgY possesses measurable in vitro antibacterial activity against E. coli and demonstrate its potential as a safe, sustainable, and residue-free complementary approach for mastitis management. Further research involving clinical mastitis isolates, antimicrobial-resistant strains, and standardized MIC determination is warranted to establish its broader therapeutic applicability and guide future in vivo studies.