Analysis of risk factors and production effects following an outbreak of bovine respiratory disease in Stocker cattle
Keywords:BRD, stocker cattle, outbreak investigation
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.