Effect of medium-chain fatty acids on growth, health, and immune response of dairy calves

It is necessary for the dairy industry to reduce calf morbidity and mortality, and the reliance on antibiot-ics to treat sick calves, to address the growing concern regarding antibiotic resistant bacteria. The primary objective of this study was to evaluate the effect that feeding dairy calves medium-chain fatty acids (MCFA) has on growth performance and health, and the second-ary objective was to evaluate the effect of MCFA on en-ergy status around weaning and the adaptive immune response following a vaccine challenge. Thirty-three Holstein bull calves (5 +/- 1.6 d of age) were randomly assigned to 1 of 2 treatments. Control (CON) calves were fed milk replacer with no C8:0 or C10:0 oil added and MCFA calves were fed milk replacer with 0.5% of a combination of C8:0 or C10:0 oil added. Body weight and average daily gain were measured weekly. Feed efficiency (gain/feed) and the change in body condition score, hip width, hip height, heart girth, and paunch girth were calculated for the duration of the study. Fecal scores were recorded daily and all medical treat-ments were documented for the duration of the trial. On d 42, 49, and 56 of the study, a serum sample was collected from each calf and used to measure nonesteri-fied fatty acids, beta-hydroxybutyric acid, insulin, and glu-cose concentrations to evaluate energy status around weaning. A subset of 11 calves per treatment were enrolled in a vaccine challenge. At 21 +/- 1.9 d of age (mean +/- standard deviation) calves were vaccinated intramuscularly with 1 mL of endotoxin-free ovalbu-min (OVA) mixed with aluminum hydroxide adjuvant. At 42 d of age ( +/- 1.9 d), blood samples were collected and used to analyze OVA-specific IgG(1) and IgG(2), and calves were vaccinated a second time. At 56 d of age (& PLUSMN;1.9 d), blood samples were collected to analyze IgG(1) and IgG(2) as well as IFN-gamma and IL-4 secreted from peripheral blood mononuclear cells (PBMC) treated with OVA or phytohemagglutinin. Data were analyzed as a completely randomized design with repeated measures when applicable. A tendency for greater daily fecal score was observed for MCFA calves compared with CON. At d 42 of the study, nonesterified fatty acid concentrations were greater in CON calves compared with MCFA. At 42 and 56 d of age, anti-OVA IgG1 concentrations for CON and MCFA calves were greater than prevaccination samples. This study suggests that feeding MCFA to calves affects the energy status of calves around weaning and vaccinating dairy calves with ovalbumin combined with an aluminum hydroxide adjuvant is an effective way to evaluate the adaptive immune responses.