This Real Science Exchange podcast episode was recorded during a webinar from Balchem’s Real Science Lecture Series.
Shakespeare wrote, “The eyes are the windows of the soul.” Dr. Ollivett believes the lungs are the window to calf health management. The lungs are an indicator organ: respiratory disease is a symptom of management failure. Failure of passive transfer, diarrhea, septicemia, poor nutrition, a dirty environment, and heat or cold stress can all negatively impact the lungs. Often, this can manifest as subclinical pneumonia, where the lungs are abnormal but the calf externally appears completely normal. (3:51)
Dr. Ollivett reviews the defense mechanisms of the airway. When a veterinarian takes swabs to assess a respiratory disease problem, the bacteria and viruses that live in the nasopharyngeal area just ahead of the trachea are the most representative of those bacteria and viruses that are present in the lungs. The bacteria and viruses in the lower nasal passages are unreliable indicators of what is present in the lungs. (6:28)
Is coughing a good predictor of pneumonia? Research shows that if calves are coughing, it is highly likely they will test positive for a respiratory pathogen. One study showed that coughing was the best predictor of observing pneumonia on lung ultrasound, but only 37% of calves with pneumonia on ultrasound also had a cough. Dr. Ollivett observed similar results in commercial settings, where only about 10% of calves with pneumonia on ultrasound had an accompanying cough. This suggests that a cough is not a good early warning tool for pneumonia. (10:29)
Dr. Ollivett believes respiratory disease exhibits an iceberg effect, where considerably more subclinical respiratory disease exists than clinical respiratory disease. She provides examples of necropsied lungs from dairy calves to emphasize the point that calves can appear completely normal, but have the same or more damage to their lungs compared to calves exhibiting clinical signs of pneumonia. In her work, Dr. Ollivett has found that the sensitivity of lung ultrasounds to find lung lesions in animals with subclinical disease is 88%. (16:32)
What does it take to perform a lung ultrasound? Dr. Ollivett gives an overview of the process and describes what normal and affected lungs look like. Depending on the farm, 50-80% of cases can be subclinical for one to two weeks before we see signs of pneumonia. With lung ultrasounds, you can treat affected animals sooner while also getting a good assessment of where management can improve to better prevent pneumonia cases in the future. (27:37)
The prevalence of the disease is roughly equal to the incidence of the disease times the duration of the disease. Prevention of disease reduces the speed at which disease occurs, thus decreasing the incidence of disease and lowering its prevalence. On the other hand, identifying sick calves sooner should reduce the duration of the disease, also lowering its prevalence. In addition, effective treatment that reduces the duration of disease supports antimicrobial stewardship. Dr. Ollivett details criteria to evaluate treatment failure in your operation, as well as discusses antibiotic therapy in conjunction with lung ultrasounds. (34:29)
Dr. Ollivett emphasizes the impact that the gut has on the lungs on most dairy farms. She feels that as an industry, we are far too comfortable with abnormal manure in 7- to 14-day-old calves. After any abnormal manure, calves are more likely to have abnormal lungs in the next couple of weeks. Ensuring good passive transfer and maintaining a clean environment will reduce lung lesions. (50:50)
To keep calves breathing easy, Dr. Ollivett shares recommendations to reduce management failures before, at, and after birth. These can include clean and adequate space in maternity, clean calf bedding and equipment, the excellent establishment of passive transfer, adequate average daily gains in early life, and routine lung ultrasounds. (53:21)
Dr. Ollivett answers questions from the webinar audience about evaluating treatment protocols for effectiveness, technicalities and landmarks of performing lung ultrasounds, how soon after birth to begin lung ultrasounds, using lung score to determine when to treat with antibiotics, and if lung ultrasounds could be used to cull animals with lung damage before they enter the milking herd. Watch the full webinar at balchem.com/realscience. (55:44)
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