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Summer lovin’: how to keep pigs comfortable as temperatures rise

Caring for pigs in summer can be challenging, with the combination of heat and increased day-length both affecting comfort.

Australian Pork Limited Manager, Production Stewardship, Dr Pat Mitchell, said pigs needed to be supported to stay in their Thermal Comfort Zone.

“The Thermal Comfort Zone is the temperature range in which the pig feels most comfortable,” Dr Mitchell said.

“How comfortable they feel is affected by a number of factors. Interactions between air temperature, skin wetness, air movement, humidity, floor type, breed and amount and composition of diets all affect comfort.

“Their lower critical temperature (LCT) and evaporative critical temperature (ECT) the two extremes and varying according to environmental interactions.”

Dr Mitchell said watching pigs would give a good indication of how pigs were coping with their environment.

“Pigs change their behaviour when they feel hot or cold,” Dr Mitchell said.

“If air temperature falls, pigs feel cold and they will huddle and change posture to conserve heat. They’ll also use more of their feed to generate body heat and less for growth and production, meaning pigs will be leaner.

“As air temperature rises above the LCT, but still in the Thermal Comfort Zone, pigs can maintain their body temperature by a number of methods. For example, if the floor is cooler than the air, they may change position so more of their skin is in contact with the floor. They may reduce contact with other pigs, plus swallow, splash and increase water consumption.”

Water is important as temperatures rise. “You’ll notice that in high temperatures, pigs are rarely dry,” Dr Mitchell said.

“They deliberately wet themselves to cool the skin through evaporation with drinking water, saliva, dung and urine. As air temperature rises to the upper limit of the comfort zone, a pig starts to pant to increase the evaporative heat loss from its lungs. This occurs at the ECT. A good measure of this point is the pig panting at around 50 to 60 breaths per minute.”

While pigs can lose more heat by increasing their respiration rate or panting, this is inefficient compared to other animals, such as dogs. “As air temperature rises above the ETC, the pig pants faster, its body temperature increases and it reduces feed intake resulting in lower growth rates,” Dr Mitchell said.

“If air temperature rises further, a temperature is reached where the pig’s evaporative heat loss from lungs and skin is greatest.

“It has no further mechanisms left to control its rising body temperature.

“This is called the Upper Critical Temperature. Air temperature above the UCT cause a dramatic rise in body temperature, often followed by death.”

The age and stage of the pig is also important in this comfort equation.

“Piglets, lactating sows, weaners and other pigs have different needs,” Dr Mitchell said.

“For example, the body temperature of piglets falls rapidly after birth, but should recover within half an hour. Young pigs are very susceptible to cold and draught because they have thin skin, sparse hair coverage and very little fat.

“By contrast, a lactating sow has much higher heat production. The difference in needs can only be met by providing a farrowing area and straw so that the sow is kept within its Thermal Comfort Zone, while the bedding protects the piglets.”

So what can producers and staff do to keep pigs comfortable?

“For any class of pig, a high degree of stockmanship is required to provide the correct temperature,” Dr Mitchell said.

“For example, a pig may be too cold at 25 degrees in a strong breeze, but too hot if the air is slow-moving and humid.

“Even at high temperatures, pigs can feel comfortable when good ventilation is combined with wallows or spray or drip cooling.”

Dr Mitchell said rather than using a maximum/minimum thermometer to monitor pigs’ comfort, observation of behaviour was the key sign.

“If pigs huddle together or shiver, they are obviously too cold,” she said.

“If their dunging behaviour changes, causing dirty areas or they’re lying scattered across the floor panting, the pigs are suffering from high temperatures.

“Data loggers can measure daily temperature extremes, tracing hourly temperatures for periods of days or weeks and allowing you to download information and see what is happening, but really, regular observations of pig comfort are necessary.” 

“Keeping pigs comfortable is important for their welfare, but it also helps with your overall productivity,” Dr Mitchell said.

“If pigs are too cold, eat more feed to maintain their body temperature, but it’s not transformed to growth and condition. If they’re too hot, they will reduce their food intake, also affecting growth and condition.

“A happy, healthy pig is what we all want, so keeping a close eye on their environment and keeping them in their Thermal Comfort Zone helps deliver that.”

FYI:

Lower Critical Temperature: when pigs feel cold, they will huddle and change posture to conserve heat. More of the food eaten is used to generate body heat, leaving less energy available for growth and production. There will be less body fat deposited and pigs will be leaner.

Thermal Comfort Zone: the temperature range in which the pig is most comfortable. Behaviour will change to adapt as temperature rises above LCT but within this range. 

Evaporative Critical Temperature: the upper limit of the pig’s comfort zone.

Upper Critical Temperature: the pig has no further mechanisms left to control its rising body temperature. This is a danger zone.

Practical air temperature ranges between LCT & ECT[1]

Suckers(birth-weaners) 32-380C
Weaners (weaning-8 weeks) 30-220C
Growers/Finishers 20-240C
Dry sows/boars 18-240C
Lactating sows 18-220C

[1] From “Plan it Build It” 1994

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