Spray and drip cooling systems for piggeries

If there is good airflow at pig level to achieve evaporation, you can reduce heat stress in dry climates by drip or spray cooling. The water absorbs the pigs' body heat as it evaporates to cool their bodies.

Installing spray coolers

You can install spray and drip cooling systems cheaply and easily.

In a back-to-back, part-slatted pen system, you mount nozzles in a pipeline suspended from the roof structure about 1800mm over the centre partition. The spray covers the slatted portion of the pen but does not wet the pig feed. About 350mL of water sprayed on each pig over 2 or 3 minutes should evaporate in an hour (in half an hour in hotter climates so will need reapplying).

Use a drip system – instead of a spray system – for situations where you don’t want the floor to be very wet, such as for a lactating sow.

In deep litter shelters, spray the resting area, but adjust the system to avoid wet litter.

Spraying components

You should choose nozzles for their:

• uniform large droplet size
• spray angle
• flow rate.

Irrigation microjets and agricultural solid-cone spray-nozzles are the best choice because they distribute large water droplets evenly. You should only use misting or fogging nozzles with forced air ventilation systems because they increase humidity within the shed.

You need about 200kPa (kilopascals) of water pressure or 20m of head for the spray cooling system to operate properly. Higher pressures are unsuitable.

Galvanised metal pipes can be used, however PVC or polythene pipes are simpler, easier and cheaper to install. A 20mm nominal bore (NB) pipe should be adequate.

An electric solenoid valve controls the flow of water to the nozzles. The valve body is usually brass, although you can use nylon valves from washing machines if they are housed properly. The solenoid needs to be a two-way valve and is normally closed.

A filter in the pipeline before the solenoid valve is essential so the nozzles don’t get blocked by small particles, especially if your water source is a farm dam or creek.

Electrical components

If you want to automate a water spray system, you need to install a cycle timer switch and a thermostat with a remote sensing bulb to switch the power on and off.

Set your thermostat to trigger the solenoid valve when the temperature is higher than the set point (usually 26-28^oC). The system will spray your pigs continuously for the chosen minutes or until the thermostat temperature drops below the set point.

Use a remote bulb thermostat where the thermostat itself is mounted out of the way while the remote bulb is set at pig level. The thermostat should be accurate to within 1^oC.

You can also use a programmable controller unit (PCU) to set temperatures, times and length of spray. You can use the same PCU to control ventilation openings, fan speeds and heating systems, but there must be contingency plans in your electronic spray cooling system in case power fails.