This is the first study to evaluate the effect of supplementing CR with GAC on measures of passive transfer, health, and growth in commercial dairy calves. The use of 1.5 doses of CR, providing 150 g of IgG, resulted in high levels of passive transfer, with overall mean serum IgG and STP concentrations at 24 h averaging 20.2 mg/mL and 5.7 g/dL, respectively, but did not differ between CR treatments. Among all calves enrolled, only 1.2% had FPT, compared with an FPT rate of
approximately 19.2% on US dairy operations (Beam et al., 2009)