Association between the severity of lung lesions and performance, mortality, first conception, and pneumonia treatment in dairy calves

The objectives of this study were to determine the impact of lung lesions in dairy calves on weight gain throughout the pre-weaning phase, mortality until 19 months of age, and age at first conception, and its association with transfer of passive immunity (TP) and diarrhea and establish the efficiency of on-farm calf pneumonia diagnosis. Thoracic ultrasonography (TUS) was conducted on 193 Holstein calves aged 1 to 24 weeks, and data related to TP, diarrhea, weight gain, and age at first conception were collected. Out of these, 109 calves were used to compare TUS findings with on-farm diagnosis, which was based on treatment records. For each unit increase in plasma protein (TP) above 5.0 g/dL, there was a reduction in the number of lesions > 1 cm (R2= 0.0061; P= 0.003) and cases treated for pneumonia (R2= 0.021; P= 0.044), whereas more days in diarrhea represented more treatments (R2= 0.022; P= 0.04). The number of intercostal spaces (ICS) affected had a negative effect on the time required to reach a body weight of 370 kg (R2= 0.025; P = 0.001) and an increase in the mean value of the number of ICS with consolidations > 1 cm by one unit resulted in a 51% increase in the death rate (hazard ratio = 1.51; P= 0.002) up to 19 months of age. In the comparison of TUS and on-farm diagnosis, 36.69% (40/109) of the calves were misdiagnosed. These results underscore the importance of enhancing diagnostic methods and strategies for pneumonia in calves, as well as identifying and mitigating associated risk factors to improve health, future productivity, and survival.