Abstract
The objectives of this study were to: 1) to examine the effect of number of stocker cattle in a receiving pen on BRD morbidity and mortality; and 2) to examine the effect of number of stocker cattle in a receiving pen on cattle performance. Crossbred steers of unknown origin and history (n = 200) were purchased from auction barns in the southern portion of the United States. Cattle were stratified by weight and assigned to either a small (10 head/pen) or large (50 head/pen) treatment on arrival. Calves were assigned to 1 of 3 large pens or 1 of 5 small pens. Cattle were observed daily for clinical signs of BRD and treated if rectal temperature ≥40°C. Body weight was collected on d 0, 14, 28, 42, and 56. Rectal temperature was collected at arrival. Days-at-risk for BRD was the number of days from arrival until a calf: (1) was first diagnosed with BRD; (2) died; or (3) finished the trial. Treatment effects on BRD incidence and performance were tested using Poisson distribution and logistic regression using GLIMMIX or linear regression using MIXED procedure of SAS, respectively, accounting for clustering by pen. Mortality was analyzed using the LOGISTIC function with Firth’s penalized likelihood. There were 8,698 total days at risk and overall incidence density was 7.82 BRD cases per 1,000 calf days. Overall morbidity totaled 32.5% with 5.5% mortality. No difference among treatment was observed for morbidity, mortality, or performance. Cattle with fever on arrival were 1.125 times more likely to contract BRD (P ˂ .0001). The number of BRD treatments received had an effect on ADG at d 0–14 (P ˂ .0001), 0–28 (P ˂ .0001), and 0–60 (P ˂ .0001), with ADG decreasing as number of treatments increased. In summary, fever on arrival affected BRD incidence, and number of treatments cattle received affected growth throughout the trial.