On-farm Research from University of Minnesota Shows Benefit of Pasteurizing Colostrum

In the past five years there have been several university research studies into the effectiveness of pasteurizing colostrum. Penn State research showed that on average heating colostrum at 140°F for 30 minutes is the optimum combination to reduce bacteria counts without affecting colostrum IgG levels or viscosity. Work at the University of Minnesota confirmed that if higher levels of some disease-causing organisms are present in the colostrum, 140°F for 60 minutes will give a more reliable kill of these harmful bacteria; however, slightly more IgG will be lost in the process. Research also found that calves fed pasteurized colostrum absorbed more IgG. In three studies conducted by Penn State and the University of Minnesota, feeding pasteurized colostrum increased 24-hour serum IgG level by 25% and apparent absorption efficiency by 28%. A new study from the University of Minnesota looked at the implementation of colostrum pasteurization on farms to see if similar results could be achieved in the field. Results were published in the July issue of the Journal of Dairy Science.

Six farms in Minnesota and Wisconsin participated in this study, and 1,071 newborn calves were fed 1 gallon of either fresh or heat-treated colostrum within 2 hours of birth. Colostrum was collected daily on each farm and pooled into a single batch within 48 hours of collection. Half of each pool was stored in a refrigerator and the other half was heated to 140°F for 60 minutes in a batch pasteurizer. Fresh colostrum contained 63.9 mg/mL IgG, and heat treated colostrum had 61.1 mg/mL. Total plate count was 5.6 log cfu/mL for fresh and 3.5 log cfu/mL for heat-treated colostrum. Total coliform count was 4.7 log cfu/mL for fresh and 2.1 log cfu/mL for heat-treated colostrum. Heat treatment reduced total plate count and total coliform count, while IgG content was not significantly affected. Calves fed heat-treated colostrum had 18.0 mg/mL of serum IgG compared to 15.4 mg/mL for calves fed fresh colostrum, an increase of 16.88% (blood samples collected at 4 days of age on average). Efficiency of IgG absorption could not be calculated in this study because calf body weights were not measured. In addition, 36.5% of calves fed fresh colostrum were treated for an illness before weaning compared to 30.9% of calves fed heat-treated colostrum; calves fed fresh colostrum were 1.25 times more likely to be treated. Treatment for scours followed a similar pattern, and calves fed fresh colostrum were 1.32 times more likely to be treated than those fed heat-treated colostrum.

The results of this study were further analyzed to investigate why heat-treating colostrum reduces the risk of illness in calves. Total plate count and total coliform count in colostrum were found to have a negative, linear relationship with IgG level in serum. Using a statistical approach called path analysis, researchers determined that heat-treatment of colostrum improved serum IgG levels due to reduced total coliform count in colostrum. Path analysis cannot directly measure cause and effect, it simply evaluates mathematical relationships. However, previous research has shown E. coli that colonize the small intestine before colostrum feeding can be absorbed into the calf’s bloodstream and can limit the absorption of IgG. 

In summary, colostrum pasteurization can reduce bacterial loads in colostrum, improve IgG levels in calf serum, and reduce calf illnesses prior to weaning, as demonstrated in this study conducted on commercial dairy farms in the Midwest.