Title: Short communication: Behavioral attitude scores associated with bovine respiratory disease identified using calf lung ultrasound and clinical respiratory scoring
Abstract: The objective of this study was to determine whether calves exhibit differences in behavioral attitude when diagnosed with their first bovine respiratory disease (BRD) event and whether fever (≥39°C) at the time of BRD diagnosis affected attitude. Preweaned dairy calves (n = 280; 21 ± 6 d) were examined twice weekly until weaning using a clinical respiratory score (CRS; CRS+: 2 respiratory categories with scores of 2 or greater; CRS-: 1 respiratory category with a score of 2 or greater or all respiratory categories scoring less than 2), lung ultrasound, and attitude score (normal = bright, alert, responsive; depressed = dull but responds to stimulation, slow to stand, or reluctant to lie down). Bovine respiratory disease was categorized as subclinical BRD (SBRD; CRS- and lung consolidation ≥1 cm2; n = 164) or clinical BRD (CBRD; CRS+, with or without lung consolidation; n = 79). Calves without BRD (NOBRD; n = 37) remained CRS- with lung consolidation <1 cm2 for the study. Depressed attitudes were found in 23, 6, and 0% of CBRD, SBRD, and NOBRD calves, respectively. In calves with CBRD, the odds of having a depressed attitude were 5.2 (95% confidence interval, confidence interval: 1.1-23.7) and 4.5 (95% confidence interval: 2.0-10.4) times higher compared with the odds of NOBRD and SBRD calves having a depressed attitude, respectively. The odds of having a depressed attitude did not differ between SBRD and NOBRD calves. Fever was associated with the odds of having a depressed attitude score, whereby calves with a fever had 6.2 (95% confidence interval: 2.8-14) times higher odds of having a depressed attitude score compared with calves without a fever. Sensitivity and specificity of the attitude score for identifying CBRD were 23% (95% confidence interval: 14-33) and 95% (95% confidence interval: 82-99), respectively. Producers should be cautious when using this attitude score as the primary means of detecting calves affected by BRD.