Association between milk anti- <i>Staphylococcus aureus</i> antibody, somatic cell count, and milk yield in lactating dairy cows

This observational study demonstrated moderate agreement between S/P ratio and SCC. Additionally, there were negative associations between the S/P ratio and MS amongst older cows and in late lactation. Thus, the S/P ratio of an <i>S. aureus</i>-specific IgG ELISA is correlated with a well-defined marker of mastitis (SCC) and with milk yield depression. Further assessment of these associations using microbiology, and investigation of associations between the antibody results and long-term survival in the herd would further strengthen the validity and utility of the test.