Factors Affecting Serum Total Protein and Immunoglobulin G Concentration in Replacement Dairy Calves

Evaluation of dairy replacement calf health is generally divided into the pre-weaning and post-weaning periods; with an average weaning age of 8.6 weeks [1]. In 2007, the NAHMS Dairy study found that the pre-weaning period accounts for about 81% of total dairy replacement calf mortality [1]. Accordingly, management strategies to optimize health during this period will have the greatest impact on overall dairy calf mortality. Cows do not confer immunity transplacentally, but rather calves acquire protection from pathogens through ingestion of colostrum in a process called passive transfer [2]. While morbidity and mortality risks are not exclusively correlated with passive transfer status, multiple studies have reported an increased risk for morbidity and mortality in calves with low levels of circulating immunoglobulins [3-5]. Colostrum has great amounts of immunoglobulins, with the majority being Immunoglobulin G (IgG), although IgA and IgM are also present and may be important [2,68]. Immunoglobulins are absorbed by enterocytes in the gut and aid in disease prevention until the calf’s own immune systems develops [2]. In addition to immunoglobulins, colostrum contains other diseasefighting constituents, such as leukocytes, lactoferrin, lysozyme [2], and cytokines [2,9]. Colostrum also serves as an important source of nutrition for the neonate, offering richer fat and vitamin contents than whole milk [10]. Higher concentration of immunoglobulins have been associated with improved production within the herd, specifically improved average daily gain [11] and increased milk yield [12].