Abstract
In calves, failure of passive transfer（FPT）is diagnosed when the serum immunoglobulin G（IgG）level is less than the reference value at 24〜48 hours after birth. However, the reference value for FPT at 1 week of age, around when calves are transferred to growing and fattening farms, has not been established. The purpose of this study was to examine the changes in serum IgG and total protein（TP）levels in the first 7 days of life and the accuracy of FPT diagnosis at 7 days of age using these laboratory data. This study used 43 Holsteins（HS）and 34 Japanese Black（JB）calves. Blood sampling was performed at 1 and 7 days old to measure serum IgG（mg/mℓ）and TP（g/dℓ）concentrations. We found that there was a positive correlation between IgG and TP in both HS and JB calves at both ages. Using the scatter diagram of IgG vs. TP in 1-day-old calves, the diagnostic TP threshold was calculated（HS-TP, 4.6; JB-TP, 5.3）by substituting the reference value of IgG concentration（HS-IgG, 10.0; JB-IgG, 20.0）into the linear equation of the best fitted curve. HS-IgG, HS-TP and JB-IgG were significantly lower at Day 7 than those at Day 1（the average rate of change: HS-IgG, 71.7%; HS-TP, 92.2%; JB-IgG, 73.8%; JB-TP, 95.4%）. The reference value for FPT for 7-day-old calves was obtained by multiplying the reference value at 1 day old by the average rate of change（HSIgG, 7.2; HS-TP, 4.2; JB-IgG, 14.8; JB-TP, 5.1）. Seven-day-old calves were considered to have FPT when their laboratory values were below these reference values, and the results were compared to those of 1 day olds. The positive predictive value（PPV）and the negative predictive value（NPV）were 78.6% and 93.3% for HS-IgG and 76.5% and 100.0% for HS-TP, espectively. The PPV and NPV were 100.0% and 80.0% for JB-IgG and 91.7% and 86.4% for JB-TP, respectively. Thus, the concentrations of serum IgG and TP at 7 days of age can be used to determine the presence or absence of FPT in calves at an acceptable level of accuracy.
