Prognostic value of acid-base changes and clinical signs of respiratory disease severity in hospitalized dairy calves

Abstract

Bovine respiratory disease (BRD) represents a significant concern due to its negative effects on animal health, short- and long-term productivity, and substantial economic losses in both dairy and beef calves. This retrospective study aims to identify the predictors associated with outcomes in hospitalized calves affected by BRD.

From 2005 to 2020, 652 calves diagnosed with respiratory problems were admitted to the Veterinary Teaching Hospital of the University of Milan. Data on signalment, clinical signs, auscultatory findings, blood gas results, microbiological findings, and outcomes were collected. Among these, 184 Holstein Friesian calves aged 1 to 6 months (17 males and 167 females) with uncomplicated BRD were included in the study. Upon hospitalization, the calves were treated according to a standardized protocol involving antibiotics, mucolytics, and anti-inflammatory drugs. The potential clinical predictors of survival were evaluated using multivariable logistic regression. The association between predictors and outcome was considered significant when the p-value was <0.05.

Post-treatment, 130 calves were discharged in a healthy state, whereas 54 calves succumbed to the disease. A multivariable logistic regression model indicated that survival rate was significantly associated to auscultatory findings with a higher risk of survivor in calves with only increased breath sounds compared to calves with increased bronchial sound (P = 0.006; odds ratio: 7.359; 95% confidence interval: 1.857-29.156). In addition, increased base excess was found in survived calves compared to non-survived calves (P = 0.012; odds ratio: 1.14; 95% confidence interval: 1.013-1.226).

These findings suggest that calves with lower auscultatory scores are more likely to survive. Additionally, the presence of pathological bronchial sounds indicates more severe lung lesions compared to other alterations in normal breath sounds. Furthermore, a higher base excess value correlates with a better outcome. The increase in base excess indicates that the metabolic compensatory mechanisms in animals with a positive outcome effectively manage the respiratory acidosis induced by lung lesions, while in cases with a negative outcome, these compensatory mechanisms are either absent or inadequate.