A Randomized Clinical Trial Evaluating Metabolism of Colostral and Plasma Derived Immunoglobulin G in Jersey Bull Calves

Pipkin, K.M.; Hagey, J.V.; Rayburn, M.C.; Chigerwe, M.

Colostral, plasma, and serum IgG concentrations were determined using a commercial SRID kit with a serum IgG determination range 196-2,748 mg/dL, based on the manufacturer's recommendations. d Briefly, SRID plates containing specific anti-bovine IgG, agarose gel, 0.1 M phosphate buffer pH 7.0, 0.1% sodium azide as a bacteriostatic agent and 1 lg/mL amphotericin B as an antifungal agent and stored in a refrigerator at 4°C were warmed at room temperature (20-24°C) for 30 min. Aliquots (5 lL) of the provided reference serum at 3 different concentrations (196, 1,402, and 2,748 mg/dL) were pipetted into individual SRID wells on every plate used. An aliquot (5 lL) of serum, plasma, or colostrum samples were pipetted into individual SRID plate wells. The plates were incubated at room temperature (20-24°C) for 24 h. The diameters of the zones of precipitation were measured using a digital SRID plate reader e after 24 h. Serum, plasma, or colostral sample IgG concentrations were determined by comparing the diameter of the zones of precipitation with a standard curve generated by the reference serum. The regression equation generated in this manner (R 2 = 0.97-0.99) accurately predicted the inoculum IgG concentration. Minimum detectable serum IgG concentration was 196 mg/dL using the SRID. For the purposes of this study, calves determined to have serum IgG concentrations <196 mg/dL by SRID were assigned an IgG concentration of 195 mg/dL.