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From removing waste gases and disease plumes, to controlling humidity and temperature, getting air flows right in pig housing is vital to the health and welfare of livestock.

Whatever type of housing a farm has, the principles of ventilation rely on air entering and leaving a building, writes pig specialist Dr. Laura Hancox in Livestock Farming.

While that may sound simple, unfortunately it isn’t —especially in naturally ventilated buildings. However small changes can sometimes make a big difference, she says.

What is ideal air movement?

In general, one cubic meter of air per kilogram of pig should move in and out of a pig barn every hour.

However, it is also important to think about how air moves around a building.

“In the UK, air outside naturally ventilated buildings is normally colder than the air already inside the building,” says Hancox.

“This means when the air enters the building it will sink, and you don’t want cold air falling onto the laying area, you should have it falling where you want the pigs to dung.”

In naturally-ventilated building, air movement is reliant on the stack effect — which is what happens when warm air rises and leaves a building, drawing fresh air in through side openings — or side-to-side air movement.

Naturally-ventilated buildings should be designed to make use of either of these effects.

How do you know ventilation is working?

To identify whether hog house ventilation is working properly, there are three things producers can consider, Hancox writes.

First, pigs’ behaviour can give clues about whether their environment is at its optimum condition: are the animals lying and dunging where they should? Are they dirty, are they huddled, or are they showing any signs of tail or ear biting?

Second, smell the air to see if you can detect any ammonia, she advises. If humans find an atmosphere unpleasant, it’s likely pigs will too.

Finally, Hancox suggests using smoke to identify which way the air is moving.

“The traditional way is burning straw or newspaper over a barrow but health and safety suggests a proper smoke machine is a better method,” she says.

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