The rainfall over the last week has affected ground conditions on many farms, and if cattle are not already inside they will be soon. Weaning is also happening on a lot of farms with spring-born beef cattle on them, while purchasing of cattle in marts has also heated up.
Anything that causes stress in an animal’s life weakens their immune system and leaves them more vulnerable to disease.
Weaning, transportation, marts and mixing with other cattle are stressors for cattle. Without proper management, illness and disease can occur, with pneumonia being one of the main threats to weanlings.
Pneumonia is a virus spread by airborne pathogens, so keeping cool, fresh air in a shed will greatly reduce the risk of the disease spreading.
Unlike farmers in continental Europe who rely on mainly mechanical ventilation with extractor fans in place to remove the warm, stale air from sheds, we rely on natural ventilation. While a much cheaper option, it is not without its faults, mainly where there is inadequate inlet and outlet spacing.
The following are some simple steps to improve ventilation in sheds.
Create an eave outlet
While a lot of sheds have enough air coming in, there can often be an issue with an adequate outlet to remove the stale, warm air.
As a rule of thumb, there should be 0.1m² of unrestricted outlet space for each animal housed: 450mm wide for a house up to 15m wide; 600mm wide for a house up to 24m wide; and 750mm wide for larger houses.
Raise existing roof sheets
Raising sheets is a practical method to turn the roof into a ‘breathing roof’. One or two lines of sheeting per bay can be raised above the plane of the roof by about 100mm to 150mm with an overlap of about 100mm to 150mm, at each side, to prevent in-blown rain.
The raised sheets run up along the slope of the roof (which is usually across the width of the shed) and possibly up and over a round-roofed shed as well if one is present.
A wider, new sheet may have to be used to ensure sufficient overlapping to prevent rain entering the shed.
Angling of side sheeting
Side sheeting can be angled away from the wall at the bottom to increase the air inlet space along the perimeter walls
of the shed. Air is deflected upwards from the side wall as it enters. This can be done easily enough with box section steel.
Opening doors
Using doors as a supplementary air inlet is usually discouraged as it can lead to draughts, but in extremely mild conditions like we have now with little to no wind, they can be useful to allow more clean, fresh air to enter the building.
Knocking blocks
In older sheds, block walls were built up close to the eaves with no side sheeting used. The top line or two of blocks can be knocked to increase the air inlet from the side. Begin with one line and, if required, knock an additional line.
The stack effect
The stack effect works on the basis that warm air is less dense than cold air, and therefore rises up to the ridge of the roof, bringing with it any pathogens and dust. However, if there is inadequate spacing for an air outlet, then the air will cool and fall down to livestock level again, bringing with it the pathogens and dust. While we often focus on inlet spacing, outlet spacing is just if even not more critical.
How to
spot poor
ventilation
Cobwebs and black mould on sheeting and roof timbers.Stale, warm air when entering the shed when cattle are housed.Excessive sweating of cattle, as they are unable to regulate their body temperature. Adequate natural ventilation is key to controlling airborne diseases such as pneumonia at housing. Air outlet space (raised ridge or raised sheeting) is as important as inlet space. Doors should only be open to supplement air inlet spaces on muggy, calm days.Cobwebs, black mould, and warm/stale air are signs of poor ventilation.
The rainfall over the last week has affected ground conditions on many farms, and if cattle are not already inside they will be soon. Weaning is also happening on a lot of farms with spring-born beef cattle on them, while purchasing of cattle in marts has also heated up.
Anything that causes stress in an animal’s life weakens their immune system and leaves them more vulnerable to disease.
Weaning, transportation, marts and mixing with other cattle are stressors for cattle. Without proper management, illness and disease can occur, with pneumonia being one of the main threats to weanlings.
Pneumonia is a virus spread by airborne pathogens, so keeping cool, fresh air in a shed will greatly reduce the risk of the disease spreading.
Unlike farmers in continental Europe who rely on mainly mechanical ventilation with extractor fans in place to remove the warm, stale air from sheds, we rely on natural ventilation. While a much cheaper option, it is not without its faults, mainly where there is inadequate inlet and outlet spacing.
The following are some simple steps to improve ventilation in sheds.
Create an eave outlet
While a lot of sheds have enough air coming in, there can often be an issue with an adequate outlet to remove the stale, warm air.
As a rule of thumb, there should be 0.1m² of unrestricted outlet space for each animal housed: 450mm wide for a house up to 15m wide; 600mm wide for a house up to 24m wide; and 750mm wide for larger houses.
Raise existing roof sheets
Raising sheets is a practical method to turn the roof into a ‘breathing roof’. One or two lines of sheeting per bay can be raised above the plane of the roof by about 100mm to 150mm with an overlap of about 100mm to 150mm, at each side, to prevent in-blown rain.
The raised sheets run up along the slope of the roof (which is usually across the width of the shed) and possibly up and over a round-roofed shed as well if one is present.
A wider, new sheet may have to be used to ensure sufficient overlapping to prevent rain entering the shed.
Angling of side sheeting
Side sheeting can be angled away from the wall at the bottom to increase the air inlet space along the perimeter walls
of the shed. Air is deflected upwards from the side wall as it enters. This can be done easily enough with box section steel.
Opening doors
Using doors as a supplementary air inlet is usually discouraged as it can lead to draughts, but in extremely mild conditions like we have now with little to no wind, they can be useful to allow more clean, fresh air to enter the building.
Knocking blocks
In older sheds, block walls were built up close to the eaves with no side sheeting used. The top line or two of blocks can be knocked to increase the air inlet from the side. Begin with one line and, if required, knock an additional line.
The stack effect
The stack effect works on the basis that warm air is less dense than cold air, and therefore rises up to the ridge of the roof, bringing with it any pathogens and dust. However, if there is inadequate spacing for an air outlet, then the air will cool and fall down to livestock level again, bringing with it the pathogens and dust. While we often focus on inlet spacing, outlet spacing is just if even not more critical.
How to
spot poor
ventilation
Cobwebs and black mould on sheeting and roof timbers.Stale, warm air when entering the shed when cattle are housed.Excessive sweating of cattle, as they are unable to regulate their body temperature. Adequate natural ventilation is key to controlling airborne diseases such as pneumonia at housing. Air outlet space (raised ridge or raised sheeting) is as important as inlet space. Doors should only be open to supplement air inlet spaces on muggy, calm days.Cobwebs, black mould, and warm/stale air are signs of poor ventilation. 
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