Abstract
Bovine respiratory disease (BRD) is the leading cause of death in calves and can affect cattle at different ages. Dairy calves with BRD at weaning had decreased average daily gain (ADG) and decreased future milk production. However, the impacts of BRD on the lifetime growth performance of beef x dairy cattle, reared in similar systems, is unknown. The objective was to evaluate the impact of lung consolidation in calves (n=139 beef × Holstein) at weaning on feedlot growth performance and carcass characteristics. Calves were sourced from two dairies and raised in three cohorts. Calves with ≥ 1 cm(2) in at least one lobe at 4 d post-weaning via thoracic ultrasonography (TUS) were deemed to have lung consolidation (TUS+). Calves were fed milk replacer (0.84 kg/d) with ad-lib access to calf starter and water until weaned, 57 ± 14 d. At 4 ± 2 d post-weaning, calves moved to a growing farm. At 329 d of age, cattle were moved to the feedlot (60 km) where they were fed a total mixed ration ad libitum. Calf ADG was calculated by periods: pre-weaning ((1 to 4 d of age – weaning wt)/d), post-weaning ((weaning wt – 329 d wt)/d), and feedlot ((329 d wt - final wt)/d). The targeted final weight for steers and heifers was 680 kg and 635 kg, respectively. Cattle were sent to slaughter in 5 loads. Mixed linear models assessed associations of TUS+ status with ADG (pre-weaning, post-weaning, and feedlot), dry matter intake (DMI), feedlot arrival body weight (ABW), final body weight (FBW), feed efficiency (GF), hot carcass weight (HCW), dressing percentage, ribeye area (REA), marbling score, 12(th) rib fat thickness (BF), and calculated yield grade. Models included source dairy, calf ranch, and gender as fixed effects and breed as a random effect. At weaning, 35 calves were diagnosed with BRD by TUS+. There were no differences (P>0.05) between calves diagnosed with BRD and calves defined as healthy calves for ADG, DMI, ABW, FBW, or feed efficiency. Similarly, there were no differences (P>0.05) in HCW, dressing percentage, REA, BF, and calculated yield among calves diagnosed with BRD at weaning and healthy calves. However, the marbling score was greater (P=0.02) in carcasses from healthy calves (492 ± 12) compared to carcasses from calves with BRD (448 ± 18). These data suggest lung consolidation at weaning in beef x dairy cattle did not have long-term effects on growth performance but compromised marbling.