Development of a rapid calcium testing strip with metal-enhanced fluorescence for early detection of hypocalcemia in dairy cattle.

= 0.941), with 95.0% to 108.6% recovery across different milk dilutions and an average recovery of 96.7% in skim milk, confirming its robustness against matrix effects in the target biological fluids. The functional detection range, spanning from a limit of detection of 431µM to 1.1 mM, and with a limit of quantification of 616 μM, effectively covering the critical diagnostic window for subclinical hypocalcemia (< 1.1 mM). Additionally, the test strips demonstrated long-term stability, maintaining performance for at least 120 days when stored at 4 °C. Lastly, the simple dipping-based sample application was validated as statistically equivalent to pipetting, showing potential for adaptation to farm use. This simple, portable technology could significantly improve herd health management with the potential to enable rapid, on-site screening for subclinical hypocalcemia, facilitating early treatment, and reducing the economic burden due to milk fever.