The results of the performed ROC analysis to distinguish the best biomarkers for detecting kidney injury in premature calves with RDS showed that Cys-C concentration at the cut-off point of 398.38 pg/mL, area under the curve (AUC) 0.934 (95% confidence interval (CI) 0.859–1.000; p < 0.001), with 90% sensitivity and 89% specificity, NGAL concentration at a cut-off point of 10.02 ng/mL, area under the curve (AUC) 0.957 (95% confidence interval (CI) 0.913–1.000; p < 0.001), with 100% sensitivity and 85% specificity were the most eligible markers to the diagnosis of AKI (Table 5; Figure 1A). The gene discussed is LCN2; the disease is acute kidney injury.