Effect of heat treatment of bovine colostrum on bacterial counts, viscosity, and immunoglobulin G concentration

A study was conducted to identify the optimal temperature and time at which heat treatment of bovine colostrum would least change viscosity and IgG concentrations yet reduce bacterial count. First-milking colostrum with >50 g of immunoglobulins/L (measured by colostrometer) was collected from 30 Holstein cows. Aliquots of colostrum were heated for 0, 30, 60, or 90 min at 57, 60, or 63 degrees C in a water bath. Samples were examined for viscosity, IgG(1), and IgG(2) concentrations, standard plate count, coagulase-negative staphylococci, environmental streptococci, coliform, gram-negative noncoliform, Streptococcus agalactiae, and Staphylococcus aureus counts. All heat treatments reduced counts of all bacteria groups measured compared with untreated colostrum samples. Heat treatment at >= 60 degrees C denatured IgG(1) compared with untreated colostrum; however, colostral IgG(2) levels were not reduced when temperature was held at 60 degrees C for <60 min. Viscosity was not affected when temperature was held at 60 degrees C for <60 min. In this study, heat treatment of bovine colostrum at 60 degrees C for 30 or 60 min reduced bacterial count, slightly reduced IgG concentration, and did not affect viscosity.