Best Practice Tips
Controlling Bovine Respiratory Disease requires the correct balance between the level of infectious agents to which the calf is exposed (challenge) and the calf’s resistance to those agents (immunity). Therefore in addition to vaccination, effective control of BRD involves managing the herd to reduce the trigger factors, particularly through improvements to housing and general calf health.
A building’s ventilation plays a vital part in the respiratory disease complex. Good ventilation builds a uniform air flow whether it is calm or windy outside, ensuring that excess moisture, heat and dust, gases and germs all escape from the building, creating a healthy environment for the herd.
Naturally ventilated buildings rely on heat generated by calves to heat the air, which rises and exits through outlets in the roof. This then draws air in through inlets in the walls. This is known as ‘the stack effect’ and ensures fresh air circulates in the building - even on the stillest of days.
Effective ventilation helps to reduce the level of infectious agents circulating in the shed and reduces gases such as ammonia and slurry gases which can be harmful to the respiratory tract. If a building is poorly ventilated, the warm air that animals breathe out cannot escape, so it condenses and falls, creating the ideal environment for the viruses and bacteria that lead to respiratory disease to multiply.
The stack effect gives efficient ventilation:
- Animals breathe out warm air which rises and escapes from the highest point of the building (the outlet)
- This creates negative pressure within the building which draws fresh air back in through the inlets
- Doors are not suitable inlets; they create drafts, give fresh air in only one area, and are closed too easily
The quality of a building’s ventilation can be assessed by using smoke cartridges. These release smoke in to the building and how, or whether, it dissipates gives a good idea of the quality of ventilation. The test should be carried out when the building is full of stock (to get the stack effect) and when the air is still (to ensure that any wind does not skew the results). In a well ventilated building, the smoke will pass out through the outlets in the top of the building. If it hangs in the building there is a problem.
It is often a good idea to also test specific areas in a building – even if ventilation is good in the centre, there may be corners where ventilation is less good. In fact, research shows nearly half of all naturally ventilated buildings do not supply adequate airflow for the amount of cattle housed.
Adequate ventilation is a long-term investment so you should seek professional advice when constructing or changing buildings.
Overstocking a building is detrimental for two reasons:
- More animals means more infectious agents are breathed out increasing the challenge level in the building
- Cattle produce large amounts of moisture. Increased stocking increases air moisture levels allowing bacteria and viruses to survive for longer
You therefore need to ensure that stocking levels are correct, especially in sheds which may not be ventilating adequately.
Protect against parasites
Lung damage caused by lung worm can cause respiratory disease at grass and increase the risk of pneumonia soon after housing when animals are exposed to viruses and bacteria as well. A vaccine is available to protect against lungworm, or alternatively control can be achieved through use of an appropriate endectocide or anthelmintic treatment programme. If cattle can be treated some weeks before housing this helps ensure they are free of lungworm and therefore healthier when housed, reducing one of the risk factors at this stressful time. Some endectocides (for example Cydectin® Pour-On for Cattle) allow treatment up to 5 weeks pre-housing which, for convenience, could coincide with vaccination against the respiratory viruses.
Continued vaccination - Once started, keep going
As the risk factors of respiratory disease will often still be present, it is important to continue with a vaccination programme once it has been established. It can be tempting to stop after a few years when vaccination has been successful and disease incidence is low. However, even if disease pressure was lower the previous year due to a mild winter, weather is highly unpredictable so disease can easily return.
What Farmers are Saying
Find out from those who have already experienced SureCalf what they have to say about the programme.
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