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Cooling and heating systems
Pig housing should be constructed to protect your pigs from:
- adverse weather
- sudden temperature changes
- extreme temperatures.
Your piggery must meet the requirements for heating, cooling and ventilation. Meeting the pigs' requirements starts with the external design of the shed.
The cheapest and most effective way to cool your pigs' environment is to use water spray-cooling and ducted ventilation systems.
Young pigs need warmth to grow, so you need to heat and insulate your farrowing and weaner areas to provide the correct temperature for them, especially in cold weather.
Healthy temperature ranges for pigs
Pigs are more susceptible to cold temperatures when they are young and to hot temperatures when they older (as heavy growers and adults).
Ideal temperature ranges
The ambient temperature range that suits your pigs' comfort and productivity is called the 'thermoneutral zone'. In this zone, your pig's heat production is determined by its live weight and feed intake because it is not affected by air temperature.
This is generally between 15 and 30°C but depends on:
- flooring type
- air flow
- skin wetness
- whether pigs are group housed.
The pig welfare code lists the lists the optimum temperatures for pigs at different stages.
Keeping pigs cool
The top limit of the thermoneutral zone is called the 'evaporative critical temperature' (ECT). If your pig's temperature goes above the ECT, your pig overheats and it will:
- avoid body contact with pen mates
- eat less
- foul areas of its pen that it normally keeps clean, then possibly lie in this and other wet areas
- pant more than 50 breaths a minute (this cools their bodies through evaporation from the lungs).
The 'upper critical temperature' (UCT) is the highest possible temperature your pig can reach before it starts to get serious health problems. The UCT is generally 6–8°C above the ECT. Your pigs will become severely distressed if their temperature rises above the UCT.
Avoid heat stress
Observe the pigs' behaviour, especially lactating and pregnant sows, for signs of heat stress, such as panting.
Then, lower their temperature by:
- increasing airflow
- wetting their skin
- giving ice licks.
Drip or spray cooling
If there is good airflow at pig level, you can reduce heat stress in dry climates by drip or spray cooling.
Keeping pigs warm
The lower limit of the thermoneutral zone is set by the 'lower critical temperature' (LCT).
Piglets and weaners suffer from cold more than older pigs. The best temperature for your newborn piglets is between 27°C and 35°C. You can lose piglets if the temperature falls below 16°C. Below 2°C your piglets will die within minutes.
Older pigs can be in cooler temperatures for short periods without it affecting their health, but they will eat more and produce more waste, which lowers your piggery's food conversion efficiency. Generally, the older your pig, the lower its LCT.
The pig welfare code recommends that you monitor your herds if temperatures fluctuate more than 10°C per day.
Ventilation systems in piggery sheds
Commercial ventilation and cooling systems use automate adjustment of items such as fans, sprays, heaters and shutters to achieve the pigs' comfort zone.
Ventilating air must be directed so it creates air circulation within your shed without draughts flowing directly on to your pigs, especially young pigs and in cooler weather.
Under the pig welfare, you must have failsafe backups in sheds with automated ventilation in case of power failure. Naturally ventilated sheds that rely on automated equipment must be inspected at least twice a day or have failsafe backups or an alarm to warn of a breakdown.
Observation of the pigs' behaviour is important when adjusting ventilation and cooling, not just relying on a set temperature.
Fans
Fans can improve ventilation, but they only affect a small area and you have little control over air direction or speed. Also, air won't circulate to partitioned areas. Fan systems can be properly designed by engineers.
Air quality
Fresh air must be introduced into your piggery to remove:
- water vapour
- carbon dioxide
- ammonia
- airborne dust
- bacteria
- odours.
The pig welfare code lists the maximum levels for pollutants in air.
Shed design
Ventilation in a shed depends on the shed design and type:
- closed sheds have automatically controlled temperature and ventilation (and fail-safe systems if there is a power outage)
- naturally ventilated sheds are narrow to allow good ventilation (and may also have automatically controlled temperature systems).
You can improve shed ventilation by opening up areas of the walls and roof:
- increase the area of your sidewall openings. Ideally, the sidewall opening should be able to be fully opened to get the best air circulation for your sows and growers
- install a 2 shutter system, 1 above the other, for flexible adjustment. Shutters can be linked to a thermostat to automatically adjust opening.
- build ridge vents into the roof to allow warm air to leave a wide shed (wider than 10m and usually a steeper roof pitch). Contact an agricultural engineer to design the correct size of the opening – a rule of thumb is 10% of the floor area for grower and adult pig sheds.
Make sure there are no nearby trees and foliage to block natural breezes. Trees and other sheds should be distant by at least 5 times the shed's height for good ventilation.
Poly-ducted ventilation
Ducted airflows let you control ambient temperature and spreads fresh air to virtually any area. Poly-ducted ventilation is cheaper and is easier to install and use than steel-ducted systems that can corrode in piggeries. It is often added to wide, naturally ventilated sheds to improve ventilation.
Talk to a ducted ventilation supplier for advice about the best system for your shed.
Design and size
Polythene ducts direct air from a fan through a polythene tunnel that has holes so the air escapes and spreads over your pigs. The size of the duct depends on how fast you need the air to go through. There has to be enough air pressure for the flow to reach the pigs, but if it is too fast and the duct is too small it will flap and eventually wear out.
Polythene ducted ventilation systems need to be tailored to each of your buildings. The holes are made in the duct using a hole-punch, scalpel and a template. The holes are spaced evenly to make sure air spreads evenly and reaches the far end of your system. If the holes are too large the duct will collapse because the fan can't keep the duct inflated.
Duct material
There are 2 types of polythene for piggery ducts that provide efficient airflow and longevity:
- woven polyethylene fabric – sewn or heat-welded into the duct shape
- extruded polythene tubing – a ready-formed duct and the cheapest alternative.
Choose your ducting based on the ease of use, and how long the material lasts.
Extruded polythene can be black or clear. Piggeries often prefer clear polythene as it shows rodents in the duct before they do damage. Clear polythene ducting lasts about 5 years. Make sure clear polythene ducts are between 150–250 micrometres thick.
Normally cooling designs call for tubing that is 557mm in diameter. You can use smaller diameters to duct heated air from central oil or gas-fired heaters in farrowing and weaning buildings.
The duct is suspended – usually by a thin wire that runs inside the duct's top edge – so that either a piece of tie wire or a fence netting fastener can attach the duct (at approximately 1800mm spacings) to either the roof structure or a length of wire strung above the line of the duct. The duct's far end is closed off by folding and fixing it neatly back on itself. The duct must not have any bends in it and is usually lightly tensioned. When deflated, the duct will hang down from its top edge. Ensure it has sufficient clearance available so that it does not hang into pig pens or obstruct access.
Ventilation fans
Ducted air ventilation systems commonly use axial flow propeller fans or package evaporative coolers. The fan's capacity is needed for the design and it should be the capacity at a head of 6mm water gauge. It is preferable to mount the fan on the end wall of your piggery to draw in fresh outside air.
Transition pieces
The transition piece is a section of sheet metal ducting that connects the larger fan diameter to the smaller duct. It is a truncated cone in shape and the length is twice the fan's diameter. Having 4, or preferably 8, radial fins inside the transition piece will straighten the airflow.
Control systems
Automatic fans and shutters need a fail-safe system to open shutters in case there is a power failure and the temperature rises above safe levels.
Insulation
Ventilation systems may reduce the temperature in your shed, so it's important that you insulate the roof and walls to reduce heat loss by conduction.
Insulation protected by a vapour barrier reduces condensation inside pig sheds (some insulation forms its own vapour barrier). This protects interior linings and reduces the amount of ventilation you need to prevent condensation in your building. Insulation also reduces the shed heat load in hot weather.
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 26-28oC). 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 1oC.
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.
Piggery heating systems
Older growers and mature pigs can withstand low temperatures but young pigs are very susceptible to low temperatures.
Piglets can die if the ambient temperature falls below 16°C. Monitor recent weaners during cold weather – if they are huddled then they are cold.
Protect piglets
Piglets are susceptible to low temperatures, so keep indoor piglet areas warmer than 16°C.
The pig welfare code recommends that you provide litter bedding (dry straw or untreated wood shavings) and insulation or heating for piglets under 3 weeks.
Avoid draughts
You should eliminate draughts in cold weather, and for young pigs throughout the year, depending on the external and shed temperature.
Danger areas are:
- cracks in walls or near floor level
- open-ended trenches, which let draughts up through slats
- uncovered heat lamps which create draughts at floor level where cold air displaces hot air.
Use creep boxes or covers to keep warmth around the piglets and to reduce draughts.
Bedding
Choose bedding materials that are absorbent and comfortable.
Use nesting materials such as untreated wood saw shavings, straw or shredded paper to protect your newborn and weaned piglets. These materials can also be used for older pigs in outdoor shelters during cold weather and for deep litter shelters.
Avoid materials that:
- are slippery
- have too long straw length – can inhibit piglet ease of movement
- have high environmental bacteria levels
- are contaminated by mycotoxins or chemicals.
Creep boxes and kennels
Creep boxes or kennels can be installed in farrowing and weaning areas. They can be made from waterproof ply, with a hinged lid to easily check on the pigs. A nearly fully enclosed creep area stops draughts and uses less energy.
Your heat supply may be:
- infra-red gas
- electric or water-heated pads
- electric radiant bars or bulbs.
To build the most heat-efficient creep areas and kennels:
- choose a safe area for your heating system and creep construction to reduce fire risk
- position heat lamps so they maintain temperature without burning yet warm all piglets at the same time
- insulate pig housing to keep heat in
- seal the top of your kennels
- build heavy plastic strip doors so your piglets can access their sow.
Kennels need to be able to be opened for more ventilation in hot weather and to come apart for easy cleaning.
© The State of Queensland 1995–2024
- Last reviewed: 08 Sep 2021
- Last updated: 08 Sep 2021