In a previous Michigan State University Extension article, entitled Colostrum is the start that dairy calves need we talked about the importance of calves receiving quality colostrum soon after birth. The question for calf raisers, buyers and sellers of calves is how do we know if the colostrum management program is providing the passive immunity that is critical for the calves’ health?
Calves are born without any immune protection, unlike human babies. Therefore it is critical to achieve adequate “passive immunity” through colostrum intake within the first few hours of birth. The passive immunity is due to transferring immunoglobulins (Ig) from the dam to the calf through colostrum. We call the process of achieving this passive immunity, “passive transfer”. If calves do not receive sufficient Ig, either through delayed colostrum intake, poor quality colostrum intake or inadequate colostrum intake, we call that a Failure of Passive Transfer (FPT). FPT is defined as serum Ig levels below 10 mg/ml or serum total protein levels less than 5.2 g/dl.
So how big of a problem is FPT? Beam et al. (2009) reported that a study of 394 farms in 17 states, 19.2 percent of the heifer calves in the U.S. have failure of passive transfer and 40.7 percent of U.S. farms have at least one calf with failure of passive transfer. Other studies suggest an even higher rate. In addition, Furman-Fratczak et al. (2011) reported that morbidity (sickness) and intensity of disease were the lowest in heifer calves with serum Ig concentrations exceeding 10 mg/mL (or serum total protein conc. greater than 5.2 g/dL) at 30 to 60 hours after birth. They also reported that scours, respiratory disease and growth rate were all impacted by the level of passive transfer.
Determining the success of passive transfer has traditionally relied on taking blood samples from calves between one and two days of age and shipping them to a lab to determine the level of immunoglobulin’s in the blood. Recent research out of both Washington State University (WSU) and California Polytechnic State University has explored the use of a digital Brix Refractometer to indicate serum Ig concentration or total serum protein and determine failure/success of passive transfer. The WSU study showed that a Brix scale reading of 8.3 percent correlated with 10 mg/mL Ig in serum and that at this level the Brix Refractometer provided the best balance between true positive and false positive rates for failure of passive transfer. At 8.3 percent the Brix Refractometer identified 93 percent of calves with FPT and only misclassified 14 percent as having FPT when their serum IgG was actually ≥ 10 mg/ml.
This resent research indicates that the Brix Refractometer could be a useful on-farm tool to not only assess colostrum quality but also failure of passive transfer. Calf raisers, sellers and buyers can use the tool to determine the quality of colostrum management in newborn calves and use that information to improve management and results. Improving colostrum management programs on farms will lead to better health and growth of both heifer and steer calves, which is beneficial for animal wellbeing and farm profitability.