Westpoint Farm Vets’ Tim Potter stresses the importance of optimising the calf environment to help prevent pneumonia.
Pneumonia is a complex disease caused by multiple factors, including environmental and management-related stressors and a long list of viral and bacterial pathogens. In combination, these factors overwhelm calves’ immunity and lead to disease.
The lifetime economic cost of a case of pneumonia in a dairy heifer is estimated at £772. The biggest contributor to this figure is the increased likelihood of a calf with pneumonia dying or being removed from the herd before her first calving. Heifers that had pneumonia as calves also have a reduced in daily liveweight gain of 0.067kg/day, and produce 121.2kg less milk during their first lactation. These figures demonstrate the significant impact pneumonia can have on the long-term performance of herds, and highlight the increased-efficiency opportunities of preventing the disease.
Disease prevention
To minimise the impact of pneumonia it is vital to focus on disease prevention. Once producers are treating clinical cases the damage to calves’ lungs has already been done. Vaccination is one possible tool to help to prevent pneumonia. When considering vaccine programmes, it is important to look at each unit’s specific disease challenges and risk factors because there is not a ‘one-size-fits-all’ solution to pneumonia. Vaccines must be administered prior to the period of expected challenge rather than being given to high-risk, stressed calves under high-infection pressure.
Pneumonia’s complex nature means that no single practice for reducing its impact exists and, in fact, addressing one factor alone will often lead to poor results. Introducing a vaccination programme for a group of animals kept in poorly ventilated sheds, for example, is unlikely to resolve a pneumonia issue. Similarly, calves that do not receive sufficient colostrum will not be able to respond as well to vaccines.
Effective ventilation
Good ventilation is essential to prevent pneumonia in housed animals. Respiratory-disease-causing pathogens will not survive for long once exhaled by livestock when ventilation is effective. But in a poorly ventilated environment pathogens can survive for relatively long periods, forming a significant disease reservoir and increasing the likelihood of disease spread across a group.
Adequate ventilation will ensure there is sufficient fresh air coming into the building to replace the warm, damp air exhaled by livestock. Air should be completely changed at least every six minutes. Most housing relies on natural ventilation with the wind creating a difference in air pressure inside and outside the building that draws air through. Ventilation is also driven by the stack effect where heat generated by livestock causes air to rise and escape near the top of the building. This then draws fresh air in through the sides of the building.
Poor ventilation in existing facilities is usually due to inlets and/or outlets being absent or too small. Unfortunately, new cattle sheds are also being erected with cranked ridges even though these often only offer around 20% of the required outlet. Stocking density can also impact housing ventilation. Overstocking and understocking will have a significant impact on the stack effect and ventilation requirements.
Other things to consider when assessing the calf-house environment include reducing humidity by keeping housing as dry as possible. Typical issues to look out for include poor drainage, leaking water troughs, and poorly maintained gutters