On-farm diagnosis of latent respiratory failure in calves

Abstract

The goal of this study was to develop a method for the diagnosis of latent respiratory failure in calves with bovine respiratory disease (BRD) in farm conditions. The study involved 48 calves of the red-motley Holstein breed aged 14–28 days, with no previously experienced BRD, no dyspnea at rest, and a lack of anemia. Group I consisted of 24 calves with spontaneous or induced cough and WI clinical score of ≥5. Group II included 24 calves without spontaneous and induced cough and WI clinical score of ≤3. The determination of respiratory rate (RR), respiratory minute volume, and tidal volume in all calves was performed before and after functional exertion with a 15-min run and 30-s apnea. Blood samples were obtained from the jugular vein before 30-s apnea, then immediately after, and finally 1 min after apnea; blood gases and acid-base status were analyzed on an ABL-330, while total hemoglobin content was analyzed on a Micros-60. Tachypnea and dyspnea appeared after the 15-min run in group I calves, lasting 7.2 ± 0.4 and 3.7 ± 0.2 min. In group II calves, tachypnea lasted 3.8 ± 0.2 min, and no dyspnea occurred. Within 1 min, hypoxemia and hypercapnia caused by 30-s apnea in group II calves were compensated for due to an increase in pulmonary ventilation; in group I calves it was compensated for within more than 1 min, with presence of shallow breathing and dyspnea. The relation of RR immediately after 30-s apnea to RR before apnea showed excellent diagnostic value for detecting latent respiratory failure in the calves: area under the curve was 0.981, with cut-off point of ≥1.47, sensitivity of 95.8%, and specificity of 87.5%.