Measurement of Exhaled Nitric Oxide and Carbon Dioxide in the Breath of Beef Calves
Holland, Ben Patrick
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Two experiments were conducted to test the ability to measure exhaled nitric oxide (eNO) and exhaled carbon dioxide (eCO 2 ) in the breath of healthy beef calves and calves showing clinical signs of bovine respiratory disease (BRD) using tunable diode laser absorption spectroscopy. In experiment one, three steers (avg. initial BW = 251.8 kg) were used in a preliminary study in which two steers were challenged intra-tracheally with M. haemolytica . Breath and blood, for serum Hp analysis, were collected as well as clinical responses recorded. Prior to the challenge, eNO levels in all three calves were approximately 1 ppb. The eNO levels increased to at least 2 ppb in the challenged steers. Experiment two used 395 steer and bull calves (avg. initial BW = 218.6 22.4 kg) received from auction markets for breath measurements during a 42-d receiving trial. Upon arrival, all steers had breath sampled for eNO and eCO 2 analysis. Subsequently, all calves treated for signs of BRD were sampled as well as randomly selected clinically healthy control calves. Arrival mean eNO was 313.9 415.2 ppt and mean eCO 2 was 2.64 0.94%. No differences in eNO were found between cattle subsequently treated for BRD. Steers eventually treated for BRD exhaled higher levels of CO2 than calves never treated (P<0.05). At the time of treatment, mean eNO was 368.3 ppt and 465.4 ppt for control and treated calves, respectively (P=0.29). Opposite of arrival data, eCO 2 was higher for control than treated calves (2.62 vs. 2.03%; P<0.001). Measurement of exhaled breath was successfully incorporated into the daily activities of a research facility, and numeric trends suggest eNO may be useful in diagnosing and monitoring BRD. However, the fact that eNO levels were near lower detection limits of current instrumentation and occasional contamination by high ambient NO decreased the accuracy of the measurement.
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