Evaluation of different analytical methods to assess failure of passive transfer in neonatal calves.

The objective of this study was to evaluate different analytical methods of assessing failure of passive transfer (FPT) in neonatal calves. We hypothesized that 3 different media (i.e., centrifuged serum, centrifuged plasma, filtered plasma) and different analytical methods [i.e., ELISA, capillary electrophoresis (CE), Brix refractometer, and handheld optical refractometer] would be highly correlated with the gold standard radial immunodiffusion (RID) and would generate comparable results. Serum and plasma blood samples were collected from Holstein Friesian calves (n = 216) aged 1 to 7 d, from 2 commercial dairy herds in northeast Germany. The RID analysis showed that 59 of 216 calves (27%) had serum IgG concentrations of <10 mg/mL and 157 calves (73%) had serum concentrations of ≥10 mg/mL. The mean IgG concentration (± standard deviation) was 17.1 ± 9.8 mg/mL, and the range was 0.8 to 47.8 mg/mL. In serum, the correlation between RID and CE was r = 0.97, and between RID and ELISA was r = 0.90; CE and ELISA were also highly correlated (r = 0.89). Both refractometry methods were highly correlated with RID using centrifuged serum, centrifuged plasma, or filtered plasma (Brix refractometer: r = 0.84, 0.80, and 0.78, respectively; handheld optical refractometer: r = 0.83, 0.81, and 0.80, respectively). We determined test characteristics (optimum thresholds, sensitivity, specificity, positive predictive value, negative predictive value, and area under the curve) for CE, ELISA, and the handheld optical and digital refractometers using receiver operating characteristic curve analyses with RID as the reference value. Optimal thresholds for assessing FPT using plasma were higher than for serum, regardless of the method of plasma harvesting. The 4 different devices had comparable areas under the curve, irrespective of the medium used. All analytical methods can be used to assess FPT.

Evaluation of the capillary electrophoresis method for measurement of immunoglobulin concentration in ewe colostrum.

Capillary electrophoresis (CE) is a technique routinely used in clinical laboratories that allows the separation and quantification of blood serum proteins in a rapid, precise, accurate, and inexpensive manner. Recently, CE has been proposed to separate and measure colostral proteins, but an evaluation of the agreement between CE and radial immunodiffusion (RID) method, currently used to quantify IgG in colostrum, is still lacking. The purpose of this study was to test the ability of a CE instrument, normally used in blood serum protein analysis, to realize the correct quantification of total Ig concentration in ewe colostrum, using RID assay as reference. Colostrum samples (n = 68) were collected from 35 multiparous Sarda ewes at first milking (n = 33) and at 24 h postpartum (n = 35). The mean ± standard deviation of IgG concentration measured by RID and whey colostrum total Ig concentration measured by CE were 54.76 ± 41.82 g/L and 54.70 ± 41.43 g/L, respectively. Lin's concordance correlation coefficient (r = 0.993; 95% confidence interval = 0.989 to 0.996) and linear regression analysis results (RID = 1.0022CE - 0.063; R2 = 0.986) showed an excellent agreement between these 2 methods. Bland-Altman analysis confirmed that CE method can be a suitable alternative to RID: the mean of the differences between CE and RID was -0.055 ± 4.95 g/L (95% confidence interval = -1.25 to 1.14 g/L) and the agreement limits were -9.75 to 9.60 g/L (low limit 95% confidence interval = -11.82 to -7.68 g/L; high limit 95% confidence interval = 7.57 to 11.72 g/L). In conclusion, the current study indicates that CE method may be a reliable tool for the quantification of the total Ig concentration in ewe colostrum.