Looks can be deceiving: Compensatory growth fails to offset carcass quality losses from early-life lung consolidation in beef x dairy calves

The beef × Holstein calf industry is segmented, limiting research that quantifies the long-term consequences of early life respiratory disease on the final product. The objective of this study was to evaluate the impact of lung consolidation (LC) diagnosed at weaning (61 ± 14 d) on growth performance, carcass characteristics, and liver health in beef × dairy cattle. Beef × Holstein calves (n = 143 Sire breeds Angus=51, Charolais=27, Red Angus=23, and Simmental=42) were assessed for LC using thoracic ultrasonography (TUS) at weaning and were not consolidated, or TUS + (LC ≥ 1cm). 37 TUS+ calves were pair-matched to controls by sex and cohort). Average daily gain (ADG) had three periods: arrival to weaning (P1), weaning to 83 ± 21 d (P2), and 83 d to 238 ± 21 d (P3). Following a background phase, cattle were finished in a feedlot and harvested at target weights (n = 139, 35 TUS+). Mixed linear regression models were used to assess the association of TUS+ status with ADG, and carcass characteristics (marbling, carcass dressing percentage etc.,). The odds of receiving a select quality carcass grade vs. choice or prime, and the odds of lung scarring at slaughter, were calculated using logistic regression modeling. A principal component analysis was used to assess the association of TUS+ status with explaining the variability in liver microbiomes harvested at slaughter (27 cattle). During the immediate post-weaning period (P2), controls exhibited a greater ADG (1.18 ± 0.02 kg/d) compared to calves with severe LC (≥ 1.03 ± 0.04 kg/d; P = 0.01). However, no differences in ADG were observed during P3, suggesting compensatory gain. Despite this weight recovery, detrimental effects were evident at harvest; carcasses from controls had significantly greater marbling scores (495 ± 7.82) than TUS+ cattle (462 ± 13.84; P = 0.05). Cattle that were TUS+ tended to have 3.05 increased odds of scoring select vs. choice, or prime quality grade compared to controls (OR 95% CI: 0.93 to 10.02; P = 0.06). Other carcass characteristics, such as ribeye area, hot dressing percentage, and hanging weights, were not affected. Cattle with LC at weaning tended to have 1.98 increased odds of having lung scarring at slaughter (OR 95% CI: 0.94 to 4.18; P = 0.08). There was no association of TUS+ status with explaining the variability of the liver microbiome. Overall, these results emphasize that early-life respiratory status is a critical predictor of final carcass value, even when organ-specific microbiomes remain unaffected.