Case report: Analysis of risk factors and production effects following an outbreak of bovine respiratory disease in Stocker cattle

Risk factors and production losses are reported for an outbreak of bovine respiratory disease (BRD] in stocker cattle in a southeastern US grass-based system. Beef calves purchased from livestock auctions arrived in 2 groups 1 week apart (n=133 and 77, respectively]. Cattle were mass- medicated with antibiotics and vaccinated 3 days after arrival, then commingled on ryegrass pasture. A daily BRD score (0-4] based on presence and severity of clinical signs was used to determine antibiotic treatment eligibility over the 150-day stocker phase. BRD morbidity and mortality were 61.9% and 12.9%, respectively. Cattle in arrival group 2 had a greater incidence density of BRD (rate ratio = 1.54,95% Cl: 1.07,2.22]. Odds for death were 5.0 times greater for cattle in arrival group 2 (95% Cl: 2.0,12.2] and 42.5 times greater for cattle diagnosed with BRD (95% Cl: 2.5,713.2]. Average daily gain was decreased 0.15 lb/day (0.07 kg/day] in cattle with BRD. Including death loss, calves with BRD gained an average of 64.1 lb (29.1 kg] less than unaffected calves over the stocker phase. Despite metaphylaxis and prompt identification of sick cattle, this BRD outbreak resulted in high morbidity, mortality, and production loss in a stocker cattle system.