A randomized controlled clinical trial was conducted using 1,071 newborn calves from 6 commercial dairy farms in Minnesota and Wisconsin, with the primary objective being to describe the effects of feeding heat-treated colostrum on serum immunoglobulin G concentration and health in the preweaning period. A secondary objective was to complete a path analysis to identify intermediate factors that may explain how feeding heat-treated colostrum reduced the risk for illness. On each farm, colostrum was collected each day, pooled, and divided into 2 aliquots; then, one aliquot was heat-treated in a commercial batch pasteurizer at 60°C for 60. min. Samples of fresh and heat-treated colostrum were collected for standard microbial culture (total plate count and total coliform count, cfu/mL) and for measurement of immunoglobulin G concentrations (mg/mL). Newborn calves were removed from the dam, generally within 30 to 60. min of birth, and systematically assigned to be fed 3.8. L of either fresh (FR, n = 518) or heat-treated colostrum (HT, n = 553) within 2. h of birth. Venous blood samples were collected from calves between 1 and 7. d of age for measurement of serum IgG concentrations (mg/mL). All treatment and mortality events were recorded by farm staff between birth and weaning. Regression models found that serum IgG concentrations were significantly higher in calves fed HT colostrum (18.0 ± 1.5. mg/mL) compared with calves fed FR colostrum (15.4 ± 1.5. mg/ml). Survival analysis using Cox proportional hazards regression indicated a significant increase in risk for a treatment event (any cause) in calves fed FR colostrum (36.5%, hazard ratio = 1.25) compared with calves fed HT colostrum (30.9%). In addition, we observed a significant increase in risk for treatment for scours in calves fed FR colostrum (20.7%, hazard ratio = 1.32) compared with calves fed HT colostrum (16.5%). Path analysis suggested that calves fed HT colostrum were at lower risk for illness because the heat-treatment process caused a significant reduction in colostrum total coliform count, which was associated with a reduced risk for illness as a function of improved serum IgG concentrations.
Bibliographical noteFunding Information:
This study was funded by a grant from the USDA-CSREES . The authors thank the owners and managers of the 6 dairy herds for their participation and support. We also thank Amber Hazel (College of Veterinary Medicine, University of Minnesota. St. Paul), Eb Ballinger (Cornell Veterinary Clinic, Cornell, WI), Jennifer Belz (Pierce Veterinary Clinic. Ellsworth, WI), and Katie Konkol (Mrdutt) (Bovine Veterinary Clinic. Ridgeland, WI) for their technical assistance.