Retracted: Evaluation of blood urea nitrogen as a new hematologic indicator associated with growth and development in newborn Hanwoo calves.

In immunologically naïve newborn calves, the intake of colostrum within 24 to 36 h after birth is responsible for the passive immunity of the calves during their first 2 to 4 wk of life. However, colostrum is important from both immunological and non-immunological perspectives. In this study, we aimed to develop a hematological diagnostic tool for newborn Hanwoo calves to diagnose the failure of passive transfer (FPT), as well as for calf growth and development, including average daily gain (ADG) and treatment frequency. Blood was collected at 12 to 24 h of age, and analyses of the complete blood count, serum biochemical profile, and blood gas were performed. Moreover, the number of treatments at weaning (up to 3 mo of age) was examined, and the body weight at birth, 3 mo, and 6 mo of age was recorded. From the total of 90 blood samples collected, the overall prevalence of FPT was 24.4% (22/90) in Hanwoo calves. Both serum total protein and blood urea nitrogen (BUN) showed significant correlations with albumin, globulin, albumin/globulin, creatinine, gamma-glutamyl transferase (GGT), glucose, and total bilirubin. Notably, only BUN was correlated with the ADG. Based on the receiver operating characteristic curve, BUN was statistically significant as a diagnostic tool for ADG with an area under the curve of 0.626 (95% confidence interval: 0.506 to 0.746; P < 0.05), and the optimal cutoff point was 7.3 mg/dL (sensitivity 0.65; specificity 0.64). The groups with BUN ≤ 7.3 mg/dL and BUN > 7.3 mg/dL showed significant differences in terms of albumin, globulin, albumin/globulin, creatinine, GGT, lymphocytes, and total bilirubin, and the results were similar to those of the comparison between the FPT and adaptive passive transfer (APT) groups. The ADG at 0 to 3 mo and 0 to 6 mo had a lower treatment frequency in the group with BUN ≤ 7.3 mg/dL. When comparing the ADG and frequency of treatment among the FPT, APT (BUN ≤ 7.3 mg/dL), and APT (BUN > 7.3 mg/dL) groups, the APT (BUN ≤ 7.3 mg/dL) group had the highest ADG (P < 0.01) and lowest treatment frequency. Therefore, in addition to the diagnosis of FPT, the analysis of BUN may be a new diagnostic tool for assessing the growth and development of calves.