Evaluation of Physiological Stress, Respiratory Vaccination, and Use of Immunostimulants in Beef and Dairy Calves
Hudson, Rachel Elizabeth
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Vaccination is a common practice to prevent bovine respiratory disease (BRD) and other diseases prevalent among the beef and dairy industries. A range in respiratory vaccination strategies are carried out with utilization of modified-live virus (MLV) and killed virus (KV) vaccines that may be advantageous under different conditions. More recently, immunostimulatory products have become available for control and prevention of BRD but their efficacy is poorly understood. Experiment 1 investigated the interaction of physiological stress and vaccine type (MLV vs. KV) in beef calves and Experiment 2 explored the safety and efficacy of different doses of an immunostimulant, pegbovigrastim, in recently weaned dairy calves. In Experiment 1, 48 crossbred beef steers were exposed to an acute (ACU) or chronic (CHR) stress model and were administered either a MLV or KV vaccine on d 0 of the study. This resulted in 4 treatments arranged in a 2 × 2 factorial consisting of ACU with killed virus vaccination (ACUKV), ACU with modified-live virus vaccination (ACUMLV), CHR with KV (CHRKV), and CHR with MLV (CHRMLV). Virus detection in nasal swabs, virus-specific antibody titers, haptoglobin, cortisol, and hematological variables were evaluated following stress model implementation and vaccination. Results indicated that CHR stress model and MLV vaccination may have more profoundly induced immune dysfunction in beef calves due to altered hematological and endocrine responses. In Experiment 2, 33 weaned Jersey bull calves were administered a commercially available immunostimulant, pegbovigrastim, using 3 different doses in attempt to validate a safe and efficacious dose for use in calves. Treatments included s.c. administration of 1.11 mg (PEGA), 2.22 mg (PEGB), and 4.44 mg (PEGC) of pegbovigrastim injection. Blood samples were collected to analyze hematological variables and functional capacities of blood neutrophils. While functional capacities of blood neutrophils were not different between treatments, leukocyte variables were increased for all treatments with greatest increases in white blood cell and neutrophil responses among PEGC. Further research investigating the interactions between the duration and intensity of physiological stress and vaccine antigen type is needed to ensure safe use in stressed beef calves. In addition, clinical investigation is needed to validate the use of pegbovigrastim as a safe and effective aid in prevention of BRD.