Objective: To evaluate exhaled N(2)O (eN(2)O), exhaled CO (eCO), and serum haptoglobin concentrations as diagnostic criteria for bovine respiratory disease (BRD) and determine whether a combination of biomarkers would be useful for predicting health outcomes of heifer calves.
Animals: 337 heifer calves newly arrived at a feedlot.
Procedures: Body weights, serum haptoglobin concentrations, and rumen temperatures were determined. Calves (n = 183) were randomly selected for breath sampling. Variables were compared among calves that remained healthy and those requiring treatment.
Results: Body weight at the time of first and second antimicrobial treatments did not differ from that at arrival, whereas body weight at the time of third antimicrobial treatment was lower. Temperature was lower at arrival, compared with that during antimicrobial treatment. Ratio of eN(2)O:eCO(2) was lowest at arrival, intermediate at the first and second antimicrobial treatments, and greatest at the third antimicrobial treatment. Ratio of eCO:eCO(2) was greater at times of antimicrobial treatment, compared with arrival. Concentration of serum haptoglobin was greatest at the time of the first antimicrobial treatment, lowest at the times of second and third treatments, and intermediate at arrival. Arrival ratios of eN(2)O: eCO(2) and eCO:eCO(2) and concentration of haptoglobin did not differ among heifers subsequently treated 1, 2, or 3 times.
Conclusions and clinical relevance: Although breath analysis was successfully implemented in a research feedlot, arrival rumen temperature, eN(2)O, eCO, and haptoglobin concentration were not accurate in predicting occurrence of BRD during a preconditioning program. However, these biomarkers might support the diagnosis of BRD.