Beat heat stress in pigs during the hot summer months

The South African summer typically arrives hot on the heels of spring. And when the mercury starts to climb, the hot summer days can turn uncomfortable very quickly (Heat stress). Being productive is almost impossible – a dilemma that is 100 times worse for pigs.

Heat loss in pigs

Pigs are not very efficient when it comes to dissipating excess heat. They have a quick metabolism that generates heat, but a thick layer of subcutaneous fat and poorly developed sweat glands. Heat stress affects pigs that weigh 50kg and above, with sows and growers typically most affected. Their ideal environmental temperature is 18 to 23°C, which can be problematic as our summers are much hotter than that.

Two physiological effects come into play when a pig experiences heat stress. Firstly, it takes a lot of energy to dissipate excess heat. Blood is dispersed by heat, so blood has to be pumped to the skin to release heat.

Secondly, feed intake will decrease. Blood supply to the pig’s intestines must be optimal for digestion and this will decrease during heat stress, leading to impaired intestinal health, digestion and nutrient absorption.

At the same time, the bond between the cells of the intestinal wall, which is an important barrier between the intestinal tract and the blood vessels around the intestines, will weaken. This will lead to toxins moving from the gut into the bloodstream, a condition known as leaky gut syndrome. This physiological reaction is the same in sows and growers, but with a different effect as each has a different production goal.

The negative effects of heat stress are indicated in Figure 1.

Beat heat stress in pigs during the hot summer months

Disadvantages for sows

During lactation, there is a tug of war between what the sow needs and what the piglets need. The lactating sow requires an ambient temperature of 16 to 18°C, whereas the piglets require a temperature of 34°C. Studies show that when the ambient temperature increases to 25°C or higher, a sow’s feed intake drops by 500g per day. This has a serious impact on milk production, which in turn is harmful to piglets. In addition, the sow’s ova for the next cycle are formed during this period and heat therefore has an effect on the next litter.

Disadvantages for growers

According to a study, pigs grow 15% less during the Brazilian summer than its winter. The feeding patterns of growers tend to change. Feed intake decreases, but increases again during the cooler parts of the day. This comes with its own set of problems, as not all the nutrients are digested and whatever is left will ferment in the large intestine, leading to issues such as redgut (Lawsonia infection). All these factors contribute to reduced growth.

Solutions for heat stress

Heat stress can be largely avoided by making a few management changes, such as adjusting feeding periods to feed only during the cooler times of the day or using only optimal housing. Various factors such as the type of floors, ventilation systems and orientation of the houses can make a big difference.

But what if these measures are in place and your animals are still struggling? This is where nutrition comes into play and a lot can be done to make life easier for sows and growers. These solutions include betaine, vitamin C, ration adjustments and essential oils.

New research on the benefits of essential oils abounds, including their beneficial effects on heat stress. Pigs, which have a natural fondness for menthol, find it easier to breathe when it is included in their feed. Eucalyptus oil has an antimicrobial effect and improves immunity, especially in the lungs.

An extract of peppers (Capsicum oleoresin) improves feed intake and has an anti-inflammatory effect on the digestive system. Cinnamon functions as an antioxidant and has a cooling effect in the intestines. A combination of these essential oils therefore promotes pigs’ defence against heat stress.

Conquer the challenge

South Africa’s hot summer months pose several challenges. Pigs require a helping hand to safely navigate the heat without a loss in production. Production losses due to heat stress have a sizable economic impact and must be limited. Don’t wait until the heat is on. Be proactive and help you pigs through the hot summer months.

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Suné Le Roux
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