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Diarrhea and bovine respiratory disease (BRD) are the most common illnesses affecting calves during the preweaning period. This retrospective cohort study aimed to evaluate the associations of diarrhea and BRD with ADG, relative ADG (relADG; % of ADG relative to mid-point BW), milk replacer refusal (MRR), starter intake, and mortality in Holstein and beef-on-dairy (BxD) calves during the first 56 d of life. A total of 240 newborn calves (114 Holstein and 126 BxD) were enrolled between September 2023 and March 2024, and were housed individually for 56 d, bottle-fed with 6L/d of milk replacer and had ad libitum access to calf starter and water. Diarrhea was defined as the presence of watery feces accompanied by dehydration, whereas BRD diagnosis was based on a clinical scoring system including cough (2), eye discharge (2), abnormal respiration (2), nasal discharge (4), ear droop or head tilt (5), and rectal temperature ≥39.2°C (2); BRD was defined as a total score ≥5. Both diseases were evaluated daily by the research team. Body weight was assessed at enrollment and 56 d later. Survival analyses and linear regression models were fitted to the data. The associations between BRD and diarrhea with ADG were specific to breed. Among BxD, the ADG (95% CI) was 0.42 (0.36-0.48) and 0.60 (0.56-0.63) kg/d for calves with and without diarrhea, whereas that for Holstein calves was 0.45 (0.39-0.52) and 0.51 (0.49-0.55) kg/d for calves with and without diarrhea. Additionally, lower ADG associated with BRD was only observed among Holstein calves (BRD = 0.44kg/d 95% CI: 0.39-0.49, no-BRD = 0.53 kg/d 95% CI: 0.49-0.57), as no differences were observed among BxD calves. However, relADG was only associated with diarrhea, and it was not breed specific. Milk replacer refusals were greater for calves diagnosed with BRD, but the association between diarrhea and MRR was specific to breed, with a grater difference observed in BxD calves than for Holstein. Diarrhea and BRD were both linked with lower starter intake throughout the study, but only diarrhea was associated with higher mortality. Our findings suggest that BRD and diarrhea were associated with lower growth performance and feed intake of preweaning Holstein and BxD calves.
Moreira et al. (Thu,) studied this question.