Evaluation of Two Methods to Prevent Bovine Respiratory Disease in Growing Cattle
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Bovine Respiratory Disease (BRD) is the leading cause of morbidity and mortality in the cattle feeding industry. High impact and cost of BRD necessitates development of preventative mechanisms to improve animal health, performance, and well-being and to augment the sustainability of beef production. Two potential mechanisms to prevent disease were investigated: through metaphylactic therapy (or the on-arrival mass medication of a group of high-risk cattle to control BRD) and through manipulation of dietary energy intake. A trial was conducted to determine the effects of on-arrival metaphylaxis in beef cattle for controlling BRD and the subsequent effects on health and performance. Male calves in a randomized complete block design (n=198) received ceftiofur crystalline free acid (EXC), tilmicosin phosphate (MIC), or were not treated (CON). Significant differences were not observed in morbidity rates (P = 0.14) between cattle on the MIC (46.4 ± 4.32%) or EXC treatments (56.5 ± 4.32%). Both the MIC and EXC treatments effectively reduced overall morbidity and delayed onset of clinical illness in newly received beef cattle. Furthermore, this reduction in overall morbidity was achieved with minimal increase in total antimicrobial usage. While overall performance outcomes were not different, animal health was improved with metaphylaxis. A second trial was conducted to determine the effects of limit-feeding growing steers on immune function. Thirty-two steers were fed the same ration at one of three intake levels (low, medium, or high DMI). All steers were vaccinated on study d-0 with a five-way modified live vaccine, which acted as an immunological challenge to measure immune function. Energy intake affected serum neutralizing antibody response to vaccines, and therefore overall immune function, in growing cattle. Future research should establish an ideal window of energy intake for growing cattle where both performance and health are optimized.
Word, Alyssa Brook (2014). Evaluation of Two Methods to Prevent Bovine Respiratory Disease in Growing Cattle. Master's thesis, Texas A & M University. Available electronically from