Heat stress in pigs is a frequent problem that affects pig farms and must be prevented in time. How to avoid heat stress in swine production?

Pig heat elimination mechanisms

Pigs are animals that do not have developed sweat glands. Therefore, they cannot eliminate excess heat through sweat like other animals such as horses.

Pigs have a limited ability to remove body heat. Because of this, pigs seek out muddy and watery areas to lie down and bathe in mud. This layer of mud and contact with water allows them to remove heat (Thermoregulation). Animals eliminate heat in 4 ways:

1. Evaporation: this is the removal of heat by eliminating water through respiration or sweating. This mechanism in pigs is limited compared to other species but removes 30% of the heat.
2. Convection: transfer of heat from the body to air or water particles. In pigs, it represents 30% of heat loss.
3. Radiation: loss of body heat through electromagnetic waves (infrared) to the environment. In pigs, it represents 25% heat loss.
4. Conduction: is the transfer of body heat by contact with colder surfaces. In pigs, 15% of heat is eliminated by this route.

General effects of heat stress in pigs

When pigs are incapable to remove heat, they can enter a state of hyperthermia. This hyperthermia effect has severe consequences for the animals’ organs and body systems. Hyperthermia causes damage to body cells and can lead to loss consciousness. In addition, heat stress in pigs is a known problem that affects animal production. Some of the signs observed in the heat-stressed swine population are:

• Decreased feed intake: heat stress creates inappetence in animals, and they gain less daily weight. If it is a chronic problem, they begin to lose weight rapidly.
• Tachycardia and tachypnea: heat stress in pigs generates a physiological response where there is an increase in heart and respiratory rate. The body tries to maintain body balance and oxygenated tissues through these two response mechanisms.
• Depression and weakness: heat-stressed pigs may appear depressed and lying down all the time. This recumbent position on the floor removes heat by contact with the cold floor.

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Heat stress affects reproduction in pigs

The effect of heat stress also affects the reproductive aspects of both boars and breeding sows. Heat generates a cascade of physiological changes that, when the limit of tolerance is reached, can become pathological.

1. Heat affects spermatozoa: elevated temperatures can affect the thermoregulation of the testicles. For this reason, both sperm formation and sperm motility are affected. This effect can last for weeks.
2. Decreased conception rates: sows that have been served may have lower conception rates if they are heat stressed in the 15 days following service.
3. Embryo viability: Pregnant sows that suffer heat stress events may be affected systemically. Heat stress in sows’ results in decreased embryo viability and survival.
4. Stillbirths: heat stress in pigs also affects pregnant sows in their last two to three weeks, generating stillbirths.
5. Heat compromises lactation: heat stress in newborn pigs generates difficulties in lactation. In addition, the mother with heat stress consumes less feed and produces less milk.

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Prevention of heat stress in pigs

The best tool for dealing with heat stress in pigs is to prevent heat stress. This heat stress problem can be approached from several perspectives.

1. Construction of the house: The house where pig production is located should be oriented according to the direction of the sun and wind to facilitate ventilation. In addition, the roof should be high to avoid the accumulation of humidity and heat. Insulating materials can be used to prevent heat transfer from the infrastructure to the pigs.
2. Ventilation systems: In areas with high temperatures, it is recommended to install dynamic ventilation systems that allow air to be moved and cooled. These ventilation systems must be continuously maintained to ensure proper operation.
3. Complementary measures: Other complementary measures include planting shrubs around the buildings to reduce solar radiation. Sprinkling water inside the house is also useful to cool the animals.

Complementary management of heat stress

Some mechanisms can help control heat stress in pigs and benefit at critical times. This complementary management is focused on reducing the metabolic heat produced in the feeding process of sows.

1. Regulate dietary protein: Reducing dietary crude protein by 1-2% generate less metabolic energy in sows. Because the sow consumes less calorically stressed feed, the diet must be supplemented to maintain good lactation. Some of the supplements are synthetic amino acids such as lysine, tryptophan, methionine, cysteine, threonine, and valine.
2. Feed presentation: to cope with heat stress in pigs, feed presentation can be changed. Instead of supplying flours, the feed is given in fine granules. This prevents metabolic heat build-up.
3. Water supply: Water is essential to counter heat stress in pigs. It should be ensured that it is always below 20°C. In addition, salts can be added to make the animals consume more water.

CONCLUSIONS

Heat stress in pigs is one of the most recurrent problems in pig farming. Pigs have more limited heat elimination mechanisms than other species. The effect of heat stress can be very detrimental to swine production and reproduction. Preventive measures should be taken on pig farms to avoid heat stress in pigs.