Serum Immunoglobulin G Concentrations in Calves Fed Fresh Colostrum or a Colostrum Supplement

This study compared serum immunoglobulin G (IgG) concentrations in calves fed colostrum with those of calves fed a colostrum supplement containing spray‐dried serum. Twenty‐four Holstein calves were randomly assigned to 1 of 2 treatment groups (fresh colostrum or colostrum supplement). Each calf was fed 4 L of colostrum (n 1 = 12) or 4 L of colostrum supplement (n 2 = 12) via oroesophageal intubation at 3 hours of age. The concentration of the colostrum supplement fed to calves was twice the manufacturer's recommendation. The median and range values for colostral IgG concentration were 6,430 mg/dL and 1,400‐17,000 mg/ dL, respectively. Median serum IgG concentrations at 2 days of age differed significantly ( P = .001) between calves receiving fresh colostrum (3,350 mg/dL) and the colostrum supplement (643 mg/dL). Eight percent of calves force fed colostrum had serum IgG concentrations <1,000 mg/dL, whereas 75% of calves force‐fed supplement had IgG concentrations below this threshold. The calculated population relative risks for mortality associated with passive transfer for calves force‐fed colostrum and calves force‐fed colostrum supplement were 1.09 and 1.90, respectively. Force‐fed fresh colostrum is superior to the colostrum supplement studied, but the colostrum supplement has similar efficacy to routine colostrum administration practices.