Preliminary Validation of a 'Calf-Side' Test for Measurement of Serum IgG in Dairy Calves

Abstract

The importance of adequate passive transfer (APT, IgG ≥ 10 mg/mL at 24-48 h) of immunoglobulin (lg) for newborn calves is widely known in the dairy industry. Failure of passive transfer (FPT) is associated with increased risk of morbidity, mortality, reduced growth rate, and decreased production at first lactation. The gold standard test is measurement of serum IgG concentrations in an accredited veterinary laboratory using either RID or turbidimetric immunoassay (TIA) methods. Laboratory measures are accurate but expensive ($6 to $12 per sample), plus take time to ship samples and wait for results. A common on-farm test is to measure serum total protein (TP) concentrations using a hand held refractometer to indirectly predict serum IgG concentrations. This approach is inexpensive and rapid but is less accurate than direct IgG measurement in a laboratory. Calloway and others (2002) reported that serum TP concentrations of 5.0 g/dL had a sensitivity and specificity of 0.89 and 0.84, respectively, in detecting calves with FPT. Ideally, the industry would have available an accurate, rapid, convenient, and inexpensive calf-side test to measure serum IgG concentrations. The Midland BioProducts QTII™ Bovine Serum IgG test is a portable hand-held chemistry analyzer that works on the principle of a TIA method (Midland BioProducts Inc., Boone, IA). The chemistry analyzer weighs about 2 lb (0.91 kg), is about the size of a 1 L bottle and costs $1,950.00 as a one time purchase. Test kits are available in sets of 5 at approx. $7 .50 per test for the bovine species IgG. Test kits are also available for other bovine analytes including serum albumin, total protein, calcium, magnesium and phosphorus. It takes approx. six minutes to run one test. The objective of this study was to describe the test characteristics of the MBC QTII™ Bovine Serum IgG test.