Usually, I find winter calf management to be slightly easier than summer, especially with the addition of calf jackets helping to manage cold stress. This winter has been the opposite of simple — with temperatures on a roller coaster ride rivaling Steel Vengeance — that keeps me guessing as to how much to open and close my naturally ventilated calf barn.
Even if I had the advantages of positive pressure ventilation helping to manage air turns per hour, the 40-degree temperature swings can be hard on calves and humans. Factor in the high moisture in the air, and you have the perfect recipe for pneumonia.
Pneumonia and other respiratory diseases are caused by multiple factors, but the diagnosis of respiratory disease is vital to the future of your operation.
Multiple studies find respiratory distress reduces lifetime animal profits. USDA has found that 18.1% of calves experience respiratory disease before weaning and that 22.5% of all pre-weaning deaths are caused by respiratory diseases. Early detection of disease — before the animal are slow to come eat — is critical to the success of treatment and decreases cost of these diseases.
The University of Wisconsin released a standardized scoring system in the early 2000s that utilizes rectal temperature, cough score, nasal discharge and eye/ ear score on a 0-3 point scale to diagnose respiratory disease. A score of five or great being considered a respiratory disease. It is recommended that you score each calf twice per week for accurate diagnosis, which can be challenging since this system needs rectal temperature for accurate early disease detection. It is estimated that on a 100 calf operation, 20 hours per week would be needed to preform health screening using the standardized respiratory-scoring system.
New scoring system
The University of California Davis has released a new Bovine respiratory disease scoring system for pre-weaned dairy calves. This system is much simpler than the Wisconsin system; while temperature is a critical factor it is not needed for every calf. This system still uses a critical score of 5, but scores for each clinical sign is either present or absent.
This system also has a threshold score of 5 for disease diagnosis without temperature being required to reach this threshold but is a possible factor that should be considered when a score of 4 is reached without temperature. For more information and pictures for each score visit: www.vmtrc.ucdavis.edu/laboratories/dairy-epi-laboratory.
Both the Wisconsin system and California system for respiratory scoring are an excellent way for your farm to catch respiratory diseases sooner and treat in a timely manner, having a positive impact on calf survival and improve industry-wide animal welfare.
Environmental versus contagious
When you are having abnormally high numbers of respiratory disease cases, it is time to investigate the cause, which will fall into two broad categories: environmental or contagious causes.
Often environmental causes are due to poor air quality, and with some improvement in ventilation, a reduction in the incidence of respiratory disease is often found. Often poor air quality contains contaminates of ammonia, dust, humidity or microorganisms. One way to track air quality is to monitor humidity in the calf’s pen, which should be between 50% and 80%, and ammonia levels should be less than 10 ppm.
Calves often experience a micro-climate within their pens that is different from the barn, especially when solid walls are used between pens. In order to maintain air quality, it is recommended that a barn has four air changes per hour in winter and 40 in summer.
When relative humidity levels exceed 80%, mechanical ventilation may be necessary to improve calf health. Often positive pressure tube ventilation systems are the answers, but some operations successfully use negative pressure for winter ventilation without creating a draft.
The other cause of respiratory disease, contagious pneumonia, is typically not caused by poor air quality, but exposure to pathogens through contact with infected animals, infected colostrum or contaminated feeding equipment. If through working with your veterinarian, you determine that contagious pathogens are the cause of your pneumonia issues, disinfection protocols instead of better ventilation will be needed to improve your calves’ health.
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