Health, growth, and survival measures were evaluated as secondary outcomes of this study. No effect of GAC addition to colostrum replacer was found for any of the health or growth parameters measured. However, given that sample sizes were not originally calculated with health outcomes in mind, readers should interpret these results with caution. The relatively small sample size of 129 heifer calves (CON = 60; GAC = 69) might not have provided sufficient power to detect modest differences in calf health. Nonetheless, we did not observe biologically important numerical differences between treatment groups for any of the health outcomes evaluated. These results are in contrast to what was originally
hypothesized: if GAC enhanced serum IgG concentrations or reduced colonization of the gut by pathogens
such as E. coli or Salmonella spp.,