Time to review ventilation of housing for benefit of stock

FROM now on farmers will be beginning to house animals as ground conditions deteriorate. It may not be a bad idea to review ventilation in sheds especially if respiratory diseases such as pneumonia had occurred in animals during previous housing periods.

In general dust levels, temperature, humidity and air circulation should be controlled and where ventilation in existing building is not adequate – inlets and outlets may need to be modified in order to achieve this.

Normally buildings at right angle to the prevailing wind will naturally ventilate better.

However draughts at or below animal height should be avoided particularly for young animals with the bulk of air movement occurring above head height.

The chill effects of cold temperatures are intensified when combined with increased air speed or high levels of moisture at lower levels in the shed.

Ventilation is governed by air inlets and outlets in the shed.

As a rule of thumb the ridge outlet area should be 0.04m2 per animal up to 100kgs in weight rising to 0.1m2 for older animals.

The most common outlets used on sheds in Ireland are open ridges along the full length of the shed with either up stands or ridge cap to stop rain getting in.

These open ridges are generally between 0.2-0.3m wide and should be unrestricted. Space sheeting on the roof with 10mm spacing is also commonly used as outlet ventilation.

Where no outlet is available for warm air to escape then it should be rectified immediately before stock enter shed.

As regards air inlets these should be split across two side walls of the shed and should be a minimum of twice the area of the air outlet though four times the outlet area is recommended.

The air inlets should not restrict airflow but should reduce airspeed at animal height. Most farm buildings require side wall cladding that is solid to animal height with the air inlets above this level.

Cladding material with many small openings is suitable for inlet area though different makes will have different air spacing.

Typically vented sheeting has 5% in comparison with space boarding of 100mm board and 25mm gap having 20% air spacing.

This can be altered by varying size of boarding though it is not recommended to increase the size of the gap beyond 25mm.

Windbreakers typically will have 25% spacing.

Yorkshire boarding can be used where rain is getting into the shed through the spaces.

In this case two rows of vertical boards are placed offset on the walls with the inside boards positioned at the centre of the gaps between the outside boards. For Yorkshire boarding the gap between boards should not exceed 50mm.