Association Between Serum Total Protein and Immunoglobulin G Measures in Calves Fed a Whole Colostrum Derived Colostrum Replacer

Use of refractometers to measure serum total protein (TP, g/dl) is a good method for monitoring passive transfer of IgG in groups of calves. Calloway and others (2002) reported that a serum TP concentrations of 5.0 or 5.2 g/dl most accurately predicted adequate passive transfer, defined as serum IgG of 10 mg/mL. The relationship between serum TP and IgG has been determined for calves fed maternal colostrum (MC), but not for calves fed whole colostrum derived colostrum replacers (CR). The objective of this study is to describe the relationship between serum TP (g/dl) and IgG concentrations (mg/mL) at 24 hours of age in calves fed whole colostrum derived CR vs calves fed raw MC.