A cohort study was conducted in a population of crossbred feeder steers at a commercial feedlot in central Iowa. This study assessed the relationship between Whisper® lung scores taken at feedlot arrival and feeding performance and health performance. Lung scores were taken at initial processing along with individual weights. Feeding performance outcomes included average daily gain (ADG), feed efficiency (FE), hot carcass weight (HCW), dressing percentage (DRESS), marbling score (MARB), fat thickness (FAT), and ribeye area (REA). Health outcomes included treatment for BRDC (RTX), death due to BRDC (RD), being diagnosed with chronic BRDC (RC), and dying after treatment for BRDC (RCF). A causal diagram was used to inform model building for linear and logistic regression models.

A total of 401 crossbred steer calves were enrolled in the study. Health data and ADG data from 389 steers were used in the health outcomes analyses and the ADG linear regression model. Carcass data from 227 steers were used in all other feeding performance analyses. Arrival age and arrival weight were found to be significant confounders and were included in the linear regression model analyzing arrival lung score’s association with ADG. There was no significant association between arrival lung score and ADG, FE, HCW, DRESS, MARB, FAT, or REA. There was a significant increase in the odds ratio for RTX but only for calves with an arrival lung score of 5 (OR 1.27, 95% CI 1.03-1.57, p-value 0.005). There was a significant increase in the odds ratio for RD but only for calves with an arrival lung score of 4 (OR 1.06, 95% CI 1.00-1.13, p-value 0.02). There was no association between arrival lung score and being diagnosed with chronic BRDC or dying after treatment for BRDC. This study demonstrates that arrival lung score may be predictive of treatment for BRDC and death due to BRDC but more research needs to be done.